Floquet dynamical quantum phase transitions(DQPTs),which are nonanalytic phenomena recuring periodically in time-periodic driven quantum many-body systems,have been widely studied in recent years.In this article,the F...Floquet dynamical quantum phase transitions(DQPTs),which are nonanalytic phenomena recuring periodically in time-periodic driven quantum many-body systems,have been widely studied in recent years.In this article,the Floquet DQPTs in transverse XY spin chains under the modulation ofδ-function periodic kickings are investigated.We analytically solve the system,and by considering the eigenstate as well as the ground state as the initial state of the Floquet dynamics,we study the corresponding multiple Floquet DQPTs emerged in the micromotion with different kicking moments.The rate function of return amplitude,the Pancharatnam geometric phase and the dynamical topological order parameter are calculated,which consistently verify the emergence of Floquet DQPTs in the system.展开更多
We investigate the role of quantum correlation around the quantum phase transitions by using quantum renormalization group theory. Numerical analysis indicates that quantum correlation as well as quantum nonlocality c...We investigate the role of quantum correlation around the quantum phase transitions by using quantum renormalization group theory. Numerical analysis indicates that quantum correlation as well as quantum nonlocality can efficiently detect the quantum critical point in the two-dimensional XY systems. The nonanalytic behavior of the first derivative of quantum correlation is observed at the critical point as the size of the model increases. Furthermore, we discuss the quantum correlation distribution in this system based on the square of concurrence(SC) and square of quantum discord(SQD). The monogamous properties of SC and SQD are obtained. Particularly, we prove that the quantum critical point can also be achieved by monogamy score.展开更多
CePdAl has been recently recognized as a frustrated antiferromagnetic heavy-fermion compound with a pressureor field-tuned,extended quantum critical phase at zero temperature.Identifying characteristic signatures of t...CePdAl has been recently recognized as a frustrated antiferromagnetic heavy-fermion compound with a pressureor field-tuned,extended quantum critical phase at zero temperature.Identifying characteristic signatures of the emerging quantum critical phase,which are expected to be distinct from those near a quantum critical point,remains challenging.In this work,by performing ultrasonic and thermoelectric measurements down to very low temperatures in a^(3)He–^(4)He dilution refrigerator in the presence of magnetic field,we are able to obtain some crucial thermodynamic and thermal transport features of the quantum critical phase,including a frustration-related elastic softening detected by ultrasound and a Fermi-surface change probed by thermoelectric effect.展开更多
We study geometric phases of the ground states of inhomogeneous XY spin chains in transverse fields with Dzyaloshinski--Moriya (DM) interaction, and investigate the effect of the DM interaction on the quantum phase ...We study geometric phases of the ground states of inhomogeneous XY spin chains in transverse fields with Dzyaloshinski--Moriya (DM) interaction, and investigate the effect of the DM interaction on the quantum phase transition (QPT) of such spin chains. The results show that the DM interaction could influence the distribution of the regions of QPTs but could not produce new critical points for the spin-chain. This study extends the relation between geometric phases and QPTs.展开更多
Multiple quantum coherences are often employed to describe quantum many-body dynamics in nuclear spin systems and recently,to characterize quantum phase transitions in trapped ions.Here we investigate the multiple-qua...Multiple quantum coherences are often employed to describe quantum many-body dynamics in nuclear spin systems and recently,to characterize quantum phase transitions in trapped ions.Here we investigate the multiple-quantum-coherence dynamics of a spin-1 Bose–Einstein condensate.By adjusting the quadratic Zeeman shift,the condensate exhibits three quantum phases.Our numerical results show that the spectrum of multiple quantum coherence does indeed catch the quantum critical points.More importantly,with only a few low-order multiple quantum coherences,the spin-1 condensate exhibits rich signals of the many-body dynamics,beyond conventional observables.The experimental implementation of such multiple quantum coherence protocol is also discussed.展开更多
According to our scheme to construct quantum phase transitions (QPTs) in spin chain systems with matrix product ground states, we first successfully combine matrix product state (MPS) QPTs with spontaneous symmetr...According to our scheme to construct quantum phase transitions (QPTs) in spin chain systems with matrix product ground states, we first successfully combine matrix product state (MPS) QPTs with spontaneous symmetry breaking. For a concrete model, we take into account a kind of MPS QPTs accompanied by spontaneous parity breaking, though for either side of the critical point the GS is typically unique, and show that the kind of MPS QPTs occur only in the thermodynamic limit and are accompanied by the appearance of singularities, diverging correlation length, vanishing energy gap and the entanglement entropy of a half-infinite chain not only staying finite but also whose first derivative discontinuous.展开更多
The past two decades have witnessed a surge of interest in exploring correlation and coherence measures to investigate quantum phase transitions(QPTs). Here, motivated by the continued push along this direction, we pr...The past two decades have witnessed a surge of interest in exploring correlation and coherence measures to investigate quantum phase transitions(QPTs). Here, motivated by the continued push along this direction, we propose a measure which is built upon the so-called degree of coherence, and advocate using the susceptibility of our measure to detect QPTs. We show that our measure can capture both the notions of coherence and correlations exhibited in bipartite states and therefore represents a hybrid of these two notions. Through examining the XXZ model and the Kitaev honeycomb model, we demonstrate that our measure is favorable for detecting QPTs in comparison to many previous proposals.展开更多
We construct a mapped bilayer quantum Hall system to realize the proposal that two nearly flatbands have opposite Chern numbers.For the C=±1 case,the two Landau levels of the bilayer experience opposite magnetic ...We construct a mapped bilayer quantum Hall system to realize the proposal that two nearly flatbands have opposite Chern numbers.For the C=±1 case,the two Landau levels of the bilayer experience opposite magnetic fields.We consider a mapped bilayer quantum Hall system at total fillingν_(t)=1/2+1/2where the intralayer interaction is repulsive and the interlayer interaction is attractive.We take exact diagonalization(ED)calculations on a torus to study the phase transition when the separation distance d/l_(B)is driven.The critical point at d_(c)/l_(B)=0.68 is characterized by a collapse of degeneracy and a crossing of energy levels.In the region d/l_(B)<d_(c)/l_(B),the states of each level are highly degenerate.The pair-correlation function indicates electrons with opposite pseudo-spins are strong correlated at r=0.We find an exciton stripe phase composed of bound pairs.The ferromagnetic ground state is destroyed by the strong effective attractive potential.An electron composite-Fermion(eCF)and a hole composite Fermion(hCF)are tightly bound.In the region d/lB>d_(c)/l_(B),a crossover from the d→d_(c)limit to the large d limit is observed.The electron and hole composite Fermion liquids(CFL)are realized by composite Fermions(CF)which attach opposite fluxes,respectively.展开更多
We study the quantum phase transition and entanglement in the Jaynes-Cummings model with squeezed light,utilize a special transformation method to obtain the analytical ground state of the model within the near-resona...We study the quantum phase transition and entanglement in the Jaynes-Cummings model with squeezed light,utilize a special transformation method to obtain the analytical ground state of the model within the near-resonance regime,and numerically verify the validity of the analytical ground state.It is found that the ground state exhibits a first-order quantum phase transition at the critical point linearly induced by squeezed light,and the ground state entanglement reaches its maximum when the qubit-field coupling strength is large enough at the critical point.展开更多
In this article, we review our recent work on quantum phase transition in two-dimensional strongly correlated fermion systems. We discuss the metal insulator transition properties of these systems by calculating the d...In this article, we review our recent work on quantum phase transition in two-dimensional strongly correlated fermion systems. We discuss the metal insulator transition properties of these systems by calculating the density of states, double occupancy, and Fermi surface evolution using a com- bination of the cellular dynamical mean-field theory (CDMFT) and the continuous-time quantum Monte Carlo algorithm. Furthermore, we explore the magnetic properties of each state by defining magnetic order parameters. Rich phase diagrams with many intriguing quantum states, including antiferromagnetic metal, paramagnetic metal, Kondo metal, and ferromagnetic insulator, were found for the two-dimensional lattices with strongly correlated fermions. We believe that our results would lead to a better understanding of the properties of real materials.展开更多
In order to investigate the quantum phase transitions and the time-of-flight absorption pictures analyt- ically in a systematic way for ultracold Bose gases in bipartite optical lattices, we present a generalized Gree...In order to investigate the quantum phase transitions and the time-of-flight absorption pictures analyt- ically in a systematic way for ultracold Bose gases in bipartite optical lattices, we present a generalized Green's function method. Utilizing this method, we study the quantum phase transitions of ultracold Bose gases in two types of bipartite optical lattices, i.e., a hexagonal lattice with normal Bose-Hubbard interaction and a d-dimensional hypercubic optical lattice with extended Bose-Hubbard interaction. Furthermore, the time-of-flight absorption pictures of ultracold Bose gases in these two types of lat- tices are also calculated analytically. In hexagonal lattice, the time-of-flight interference patterns of ultracold Bose gases obtained by our analytical method are in good qualitative agreement with the exDerimental results of Soltan-Panahi, et al. [Nat. Phys. 7, 434 (2011)]. In square optical lattice, the emergence of peaks at(±π/a,±π/a) in the time-of-flight absorption pictures, which is believed to bea sort of evidence of the existence of a supersolid phase, is clearly seen when the system enters the compressible phase from charge-density-wave phase.展开更多
We clarify some technical issues in the present generalized effective-potential Landau theory (GEPLT) to make the GEPLT more consistent and complete. Utilizing this clarified GEPLT, we analytically study the quantum...We clarify some technical issues in the present generalized effective-potential Landau theory (GEPLT) to make the GEPLT more consistent and complete. Utilizing this clarified GEPLT, we analytically study the quantum phase transitions of ultracold Bose gases in bipartite superlattices at zero temper- ature. The corresponding quantum phase boundaries are analytically calculated up to the third-order hopping, which are in excellent agreement with the quantum Monte Carlo (QMC) simulations.展开更多
Motivated by the recent discovery of a continuous ferromagnetic quantum phase transition in Ce Rh_(6)Ge_(4) and its distinction from other U-based heavy fermion metals such as UGe_(2),we develop a unified explanation ...Motivated by the recent discovery of a continuous ferromagnetic quantum phase transition in Ce Rh_(6)Ge_(4) and its distinction from other U-based heavy fermion metals such as UGe_(2),we develop a unified explanation of their different ground state properties based on an anisotropic ferromagnetic Kondo-Heisenberg model.We employ an improved large-N Schwinger boson approach and predict a full phase diagram containing both a continuous ferromagnetic quantum phase transition for large magnetic anisotropy and first-order transitions for relatively small anisotropy.Our calculations reveal three different ferromagnetic phases including a half-metallic spin selective Kondo insulator with a constant magnetization.The Fermi surface topologies are found to change abruptly between different phases,consistent with that observed in UGe_(2).At finite temperatures,we predict the development of Kondo hybridization well above the ferromagnetic long-range order and its relocalization near the phase transition,in good agreement with band measurements in Ce Rh_(6)Ge_(4).Our results highlight the importance of magnetic anisotropy and provide a unified theory for understanding the ferromagnetic quantum phase transitions in heavy fermion metals.展开更多
We present a new model of quantum phase transitions in matrix product systems of one-dimensional spin-1 chains and study the phases coexistence phenomenon. We find that in the thermodynamic limit the proposed system h...We present a new model of quantum phase transitions in matrix product systems of one-dimensional spin-1 chains and study the phases coexistence phenomenon. We find that in the thermodynamic limit the proposed system has three different quantum phases and by adjusting the control parameters we are able to realize any phase, any two phases equal coexistence and the three phases equM coexistence. At every critical point the physical quantities including the entanglement are not discontinuous and the matrix product system has long-range correlation and N-spin maximal entanglement. We believe that our work is helpful for having a comprehensive understanding of quantum phase transitions in matrix product states of one-dimensional spin chains and of certain directive significance to the preparation and control of one-dimensional spin lattice models with stable coherence and N-spin maximal entanglement.展开更多
For the matrix product system of a one-dimensional spin-1/2 chain, we present a new model of quantum2 phase transitions and find that in the thermodynamic limit, both sides of the critical point are respectively descr...For the matrix product system of a one-dimensional spin-1/2 chain, we present a new model of quantum2 phase transitions and find that in the thermodynamic limit, both sides of the critical point are respectively described by phases |Ψa 〉=|1··· 1 representing all particles spin up and |Ψb 〉=|0··· 0 representing all particles spin down, while the phase transition point is an isolated intermediate-coupling point where√ the two phases coexist equally, which is2 described by the so-called N-qubit maximally entangled GHZ state |Ψpt =√2/2(|1··· 1 +|0··· 0). At the critical point,2the physical quantities including the entanglement are not discontinuous and the matrix product system has longrange correlation and N-qubit maximal entanglement. We believe that our work is helpful for having a comprehensive understanding of quantum phase transitions in matrix product states of one-dimensional spin chains and of potential directive significance to the preparation and control of one-dimensional spin lattice models with stable coherence and N-qubit maximal entanglement.展开更多
The atomic mass table presents zones where the structure of the states changes rapidly as a function of the neutron or proton number.Among them,notable examples are the A≈100 Zr region,the Pb region around the neutro...The atomic mass table presents zones where the structure of the states changes rapidly as a function of the neutron or proton number.Among them,notable examples are the A≈100 Zr region,the Pb region around the neutron midshell(N=104),and the N≈90 rare-earth region.The observed phenomena can be understood in terms of either shape coexistence or quantum phase transitions.The objective of this study is to find an observable that can distinguish between both shape coexistence and quantum phase transitions.As an observable to be analyzed,we selected the two-neutron transfer intensity between the 0+states in the parent and daughter nuclei.The framework used for this study is the Interacting Boson Model(IBM),including its version with configuration mixing(IBM-CM).To generate wave functions of isotope chains of interest needed for calculating transfer intensities,previous systematic studies using IBM and IBM-CM were used without changing the parameters.The results of two-neutron transfer intensities are presented for Zr,Hg,and Pt isotopic chains using IBM-CM.Moreover,for Zr,Pt,and Sm isotopic chains,the results are presented using IBM with only a single configuration,i.e.,without using configuration mixing.For Zr,the two-neutron transfer intensities between the ground states provide a clear observable,indicating that normal and intruder configurations coexist in the low-lying spectrum and cross at A=98→100.This can help clarify whether shape coexistence induces a given quantum phase transition.For Pt,in which shape coexistence is present and the regular and intruder configurations cross for the ground state,there is almost no impact on the value of the two-neutron transfer intensity.Similar is the situation with Hg,where the ground state always has a regular nature.For the Sm isotope chain,which is one of the quantum phase transition paradigms,the value of the two-neutron transfer intensity is affected strongly.展开更多
Recent experiments [Guo et al., Phys. Rev. Lett. 124 206602(2020)] on thermodynamic properties of the frustrated layered quantum magnet SrCu_(2)(BO_(3))_(2)-the Shastry–Sutherland material-have provided strong eviden...Recent experiments [Guo et al., Phys. Rev. Lett. 124 206602(2020)] on thermodynamic properties of the frustrated layered quantum magnet SrCu_(2)(BO_(3))_(2)-the Shastry–Sutherland material-have provided strong evidence for a lowtemperature phase transition between plaquette-singlet and antiferromagnetic order as a function of pressure. Further motivated by the recently discovered unusual first-order quantum phase transition with an apparent emergent O(4) symmetry of the antiferromagnetic and plaquette-singlet order parameters in a two-dimensional "checkerboard J-Q" quantum spin model[Zhao et al., Nat. Phys. 15 678(2019)], we here study the same model in the presence of weak inter-layer couplings. Our focus is on the evolution of the emergent symmetry as the system crosses over from two to three dimensions and the phase transition extends from strictly zero temperature in two dimensions up to finite temperature as expected in SrCu_(2)(BO_(3))_(2).Using quantum Monte Carlo simulations, we map out the phase boundaries of the plaquette-singlet and antiferromagnetic phases, with particular focus on the triple point where these two ordered phases meet the paramagnetic phase for given strength of the inter-layer coupling. All transitions are first-order in the neighborhood of the triple point. We show that the emergent O(4) symmetry of the coexistence state breaks down clearly when the interlayer coupling becomes sufficiently large, but for a weak coupling, of the magnitude expected experimentally, the enlarged symmetry can still be observed at the triple point up to significant length scales. Thus, it is likely that the plaquette-singlet to antiferromagnetic transition in SrCu_(2)(BO_(3))_(2) exhibits remnants of emergent O(4) symmetry, which should be observable due to additional weakly gapped Goldstone modes.展开更多
We use quantum Monte Carlo simulations to study an S = 1/2 spin model with competing multi-spin interactions. We find a quantum phase transition between a columnar valence-bond solid(cVBS) and a Néel antiferromag...We use quantum Monte Carlo simulations to study an S = 1/2 spin model with competing multi-spin interactions. We find a quantum phase transition between a columnar valence-bond solid(cVBS) and a Néel antiferromagnet(AFM), as in the scenario of deconfined quantum-critical points, as well as a transition between the AFM and a staggered valence-bond solid(sVBS). By continuously varying a parameter, the sVBS–AFM and AFM–cVBS boundaries merge into a direct sVBS–cVBS transition. Unlike previous models with putative deconfined AFM–cVBS transitions, e.g., the standard J–Q model,in our extended J–Q model with competing cVBS and sVBS inducing terms the transition can be tuned from continuous to first-order. We find the expected emergent U(1) symmetry of the microscopically Z4 symmetric cVBS order parameter when the transition is continuous. In contrast, when the transition changes to first-order, the clock-like Z4 fluctuations are absent and there is no emergent higher symmetry. We argue that the confined spinons in the sVBS phase are fracton-like.We also present results for an SU(3) symmetric model with a similar phase diagram. The new family of models can serve as a useful tool for further investigating open questions related to deconfined quantum criticality and its associated emergent symmetries.展开更多
We investigate quantum phase transitions for q-state quantum Potts models(q=2,3,4)on a square lattice and for the Ising model on a honeycomb lattice by using the infinite projected entangled-pair state algorithm with ...We investigate quantum phase transitions for q-state quantum Potts models(q=2,3,4)on a square lattice and for the Ising model on a honeycomb lattice by using the infinite projected entangled-pair state algorithm with a simplified updating scheme.We extend the universal order parameter to a two-dimensional lattice system,which allows us to explore quantum phase transitions with symmetry-broken order for any translation-invariant quantum lattice system of the symmetry group G.The universal order parameter is zero in the symmetric phase,and it ranges from zero to unity in the symmetry-broken phase.The ground-state fidelity per lattice site is computed,and a pinch point is identified on the fidelity surface near the critical point.The results offer another example highlighting the connection between(i)critical points for a quantum many-body system undergoing a quantum phase-transition and(ii)pinch points on a fidelity surface.In addition,we discuss three quantum coherence measures:the quantum Jensen–Shannon divergence,the relative entropy of coherence,and the l1norm of coherence,which are singular at the critical point,thereby identifying quantum phase transitions.展开更多
In this paper, we study the quantum phase transition and the effect of impurity on the thermal entanglement between any two lattices in three-qubit Heisenberg XX chain in a uniform magnetic field. We show that the qua...In this paper, we study the quantum phase transition and the effect of impurity on the thermal entanglement between any two lattices in three-qubit Heisenberg XX chain in a uniform magnetic field. We show that the quantum phase transition always appears when impurity parameter is an arbitrary constant and unequal to zero, the external magnetic field and impurity parameters have a great effect on it. Also, there exists a relation between the quantum phase transition and the entanglement. By modulating the temperature, magnetic field and the impurity parameters, the entanglement between any two lattices can exhibit platform-like behaviour, which can be used to realize entanglement switch.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.11475037)the Fundamental Research Funds for the Central Universities(Grant No.DUT19LK38)。
文摘Floquet dynamical quantum phase transitions(DQPTs),which are nonanalytic phenomena recuring periodically in time-periodic driven quantum many-body systems,have been widely studied in recent years.In this article,the Floquet DQPTs in transverse XY spin chains under the modulation ofδ-function periodic kickings are investigated.We analytically solve the system,and by considering the eigenstate as well as the ground state as the initial state of the Floquet dynamics,we study the corresponding multiple Floquet DQPTs emerged in the micromotion with different kicking moments.The rate function of return amplitude,the Pancharatnam geometric phase and the dynamical topological order parameter are calculated,which consistently verify the emergence of Floquet DQPTs in the system.
基金supported by the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20171397)the National Natural Science Foundation of China(Grant Nos.11535004,11375086,1175085,and 11120101005)+1 种基金the Foundation for Encouragement of College of Sciences(Grant No.LYLZJJ1616)the Pre-research Foundation of Army Engineering University of PLA
文摘We investigate the role of quantum correlation around the quantum phase transitions by using quantum renormalization group theory. Numerical analysis indicates that quantum correlation as well as quantum nonlocality can efficiently detect the quantum critical point in the two-dimensional XY systems. The nonanalytic behavior of the first derivative of quantum correlation is observed at the critical point as the size of the model increases. Furthermore, we discuss the quantum correlation distribution in this system based on the square of concurrence(SC) and square of quantum discord(SQD). The monogamous properties of SC and SQD are obtained. Particularly, we prove that the quantum critical point can also be achieved by monogamy score.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0303100)the National Natural Science Foundation of China(Grant Nos.12141002,52088101,and 11974389)+2 种基金the Fund of the Chinese Academy of Sciences through the Scientific Instrument Developing Project(Grant No.ZDKYYQ20210003)the Strategic Priority Research Program(Grant No.XDB33000000)by China Postdoctoral Science Foundation(Grant No.2020TQ0349)。
文摘CePdAl has been recently recognized as a frustrated antiferromagnetic heavy-fermion compound with a pressureor field-tuned,extended quantum critical phase at zero temperature.Identifying characteristic signatures of the emerging quantum critical phase,which are expected to be distinct from those near a quantum critical point,remains challenging.In this work,by performing ultrasonic and thermoelectric measurements down to very low temperatures in a^(3)He–^(4)He dilution refrigerator in the presence of magnetic field,we are able to obtain some crucial thermodynamic and thermal transport features of the quantum critical phase,including a frustration-related elastic softening detected by ultrasound and a Fermi-surface change probed by thermoelectric effect.
基金Project supported by National Natural Science Foundation of China (Grant Nos. 10847108 and 10775023)
文摘We study geometric phases of the ground states of inhomogeneous XY spin chains in transverse fields with Dzyaloshinski--Moriya (DM) interaction, and investigate the effect of the DM interaction on the quantum phase transition (QPT) of such spin chains. The results show that the DM interaction could influence the distribution of the regions of QPTs but could not produce new critical points for the spin-chain. This study extends the relation between geometric phases and QPTs.
基金supported by the NSAF under Grant No.U1930201the National Natural Science Foundation of China(NSFC)under Grant Nos.12274331,91836101,12135018,12204428the Innovation Program for Quantum Science and Technology under Grant No.2021ZD0302100。
文摘Multiple quantum coherences are often employed to describe quantum many-body dynamics in nuclear spin systems and recently,to characterize quantum phase transitions in trapped ions.Here we investigate the multiple-quantum-coherence dynamics of a spin-1 Bose–Einstein condensate.By adjusting the quadratic Zeeman shift,the condensate exhibits three quantum phases.Our numerical results show that the spectrum of multiple quantum coherence does indeed catch the quantum critical points.More importantly,with only a few low-order multiple quantum coherences,the spin-1 condensate exhibits rich signals of the many-body dynamics,beyond conventional observables.The experimental implementation of such multiple quantum coherence protocol is also discussed.
基金Supported by Scientific Research Foundation of CUIT (KYTZ201024)
文摘According to our scheme to construct quantum phase transitions (QPTs) in spin chain systems with matrix product ground states, we first successfully combine matrix product state (MPS) QPTs with spontaneous symmetry breaking. For a concrete model, we take into account a kind of MPS QPTs accompanied by spontaneous parity breaking, though for either side of the critical point the GS is typically unique, and show that the kind of MPS QPTs occur only in the thermodynamic limit and are accompanied by the appearance of singularities, diverging correlation length, vanishing energy gap and the entanglement entropy of a half-infinite chain not only staying finite but also whose first derivative discontinuous.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11775129, and 12174224)。
文摘The past two decades have witnessed a surge of interest in exploring correlation and coherence measures to investigate quantum phase transitions(QPTs). Here, motivated by the continued push along this direction, we propose a measure which is built upon the so-called degree of coherence, and advocate using the susceptibility of our measure to detect QPTs. We show that our measure can capture both the notions of coherence and correlations exhibited in bipartite states and therefore represents a hybrid of these two notions. Through examining the XXZ model and the Kitaev honeycomb model, we demonstrate that our measure is favorable for detecting QPTs in comparison to many previous proposals.
文摘We construct a mapped bilayer quantum Hall system to realize the proposal that two nearly flatbands have opposite Chern numbers.For the C=±1 case,the two Landau levels of the bilayer experience opposite magnetic fields.We consider a mapped bilayer quantum Hall system at total fillingν_(t)=1/2+1/2where the intralayer interaction is repulsive and the interlayer interaction is attractive.We take exact diagonalization(ED)calculations on a torus to study the phase transition when the separation distance d/l_(B)is driven.The critical point at d_(c)/l_(B)=0.68 is characterized by a collapse of degeneracy and a crossing of energy levels.In the region d/l_(B)<d_(c)/l_(B),the states of each level are highly degenerate.The pair-correlation function indicates electrons with opposite pseudo-spins are strong correlated at r=0.We find an exciton stripe phase composed of bound pairs.The ferromagnetic ground state is destroyed by the strong effective attractive potential.An electron composite-Fermion(eCF)and a hole composite Fermion(hCF)are tightly bound.In the region d/lB>d_(c)/l_(B),a crossover from the d→d_(c)limit to the large d limit is observed.The electron and hole composite Fermion liquids(CFL)are realized by composite Fermions(CF)which attach opposite fluxes,respectively.
基金Project supported by the Natural Science Foundation of Fujian Province,China(Grant No.2021J01574).
文摘We study the quantum phase transition and entanglement in the Jaynes-Cummings model with squeezed light,utilize a special transformation method to obtain the analytical ground state of the model within the near-resonance regime,and numerically verify the validity of the analytical ground state.It is found that the ground state exhibits a first-order quantum phase transition at the critical point linearly induced by squeezed light,and the ground state entanglement reaches its maximum when the qubit-field coupling strength is large enough at the critical point.
基金I am so grateful for the great contribu- tions and beneficial communications from Yao-Hua Chen, Hai-Di Liu, and Heng-Fu Lin while I am preparing this review paper. This work was supported by the National Science Foundation of China (Grant Nos. 11174169, 11234007, and 51471093).
文摘In this article, we review our recent work on quantum phase transition in two-dimensional strongly correlated fermion systems. We discuss the metal insulator transition properties of these systems by calculating the density of states, double occupancy, and Fermi surface evolution using a com- bination of the cellular dynamical mean-field theory (CDMFT) and the continuous-time quantum Monte Carlo algorithm. Furthermore, we explore the magnetic properties of each state by defining magnetic order parameters. Rich phase diagrams with many intriguing quantum states, including antiferromagnetic metal, paramagnetic metal, Kondo metal, and ferromagnetic insulator, were found for the two-dimensional lattices with strongly correlated fermions. We believe that our results would lead to a better understanding of the properties of real materials.
基金Y.J. acknowledges Axel Pelster for his stimulating and fruitful discussions. Z.L. acknowledges inspir- ing discussions with Van Chen. This work was supported by the National Natural Science Foundation of China [Grant Nos. 11074043 (Z.L.), 11274069 (Z.L.) and 11275119 (Y.J.)] and by the State Key Programs of China (Grant Nos. 2012CB921604 and 2009CB929204) (Z.L.). This work was also supported by Ph.D. Programs Foundation of Ministry of Education of China under Grant No. 20123108110004 (Y.J.).
文摘In order to investigate the quantum phase transitions and the time-of-flight absorption pictures analyt- ically in a systematic way for ultracold Bose gases in bipartite optical lattices, we present a generalized Green's function method. Utilizing this method, we study the quantum phase transitions of ultracold Bose gases in two types of bipartite optical lattices, i.e., a hexagonal lattice with normal Bose-Hubbard interaction and a d-dimensional hypercubic optical lattice with extended Bose-Hubbard interaction. Furthermore, the time-of-flight absorption pictures of ultracold Bose gases in these two types of lat- tices are also calculated analytically. In hexagonal lattice, the time-of-flight interference patterns of ultracold Bose gases obtained by our analytical method are in good qualitative agreement with the exDerimental results of Soltan-Panahi, et al. [Nat. Phys. 7, 434 (2011)]. In square optical lattice, the emergence of peaks at(±π/a,±π/a) in the time-of-flight absorption pictures, which is believed to bea sort of evidence of the existence of a supersolid phase, is clearly seen when the system enters the compressible phase from charge-density-wave phase.
基金Z. L. acknowledges inspiring discussions with Yan Chen, Ying Jiang and also thanks Tao Wang for provid- ing the QMC data and useful discussions. Z. L. wishes also to thank Dan Bo Zhang for reading and providing useful comments on this manuscript. This work was supported by the State Key Programs of China (Grant Nos. 2017YFA0304204 and 2016YFA0300504), and the National Natural Science Foundation of China (Grant Nos. 11625416, and 11474064).
文摘We clarify some technical issues in the present generalized effective-potential Landau theory (GEPLT) to make the GEPLT more consistent and complete. Utilizing this clarified GEPLT, we analytically study the quantum phase transitions of ultracold Bose gases in bipartite superlattices at zero temper- ature. The corresponding quantum phase boundaries are analytically calculated up to the third-order hopping, which are in excellent agreement with the quantum Monte Carlo (QMC) simulations.
基金supported by the National Key Research and Development Program of China(Grant No.2017YFA0303103)the National Natural Science Foundation of China(Grant Nos.12174429,and 11974397)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB33010100)。
文摘Motivated by the recent discovery of a continuous ferromagnetic quantum phase transition in Ce Rh_(6)Ge_(4) and its distinction from other U-based heavy fermion metals such as UGe_(2),we develop a unified explanation of their different ground state properties based on an anisotropic ferromagnetic Kondo-Heisenberg model.We employ an improved large-N Schwinger boson approach and predict a full phase diagram containing both a continuous ferromagnetic quantum phase transition for large magnetic anisotropy and first-order transitions for relatively small anisotropy.Our calculations reveal three different ferromagnetic phases including a half-metallic spin selective Kondo insulator with a constant magnetization.The Fermi surface topologies are found to change abruptly between different phases,consistent with that observed in UGe_(2).At finite temperatures,we predict the development of Kondo hybridization well above the ferromagnetic long-range order and its relocalization near the phase transition,in good agreement with band measurements in Ce Rh_(6)Ge_(4).Our results highlight the importance of magnetic anisotropy and provide a unified theory for understanding the ferromagnetic quantum phase transitions in heavy fermion metals.
基金Supported by National Natural Science Foundation of China(10974137)Major Natural Science Foundation of Educational Department of Sichuan Province(14ZA0167)
文摘We present a new model of quantum phase transitions in matrix product systems of one-dimensional spin-1 chains and study the phases coexistence phenomenon. We find that in the thermodynamic limit the proposed system has three different quantum phases and by adjusting the control parameters we are able to realize any phase, any two phases equal coexistence and the three phases equM coexistence. At every critical point the physical quantities including the entanglement are not discontinuous and the matrix product system has long-range correlation and N-spin maximal entanglement. We believe that our work is helpful for having a comprehensive understanding of quantum phase transitions in matrix product states of one-dimensional spin chains and of certain directive significance to the preparation and control of one-dimensional spin lattice models with stable coherence and N-spin maximal entanglement.
基金Supported by National Natural Science Foundation of China(10974137)by Educational Commission of Sichuan Province of China(14ZA0167)
文摘For the matrix product system of a one-dimensional spin-1/2 chain, we present a new model of quantum2 phase transitions and find that in the thermodynamic limit, both sides of the critical point are respectively described by phases |Ψa 〉=|1··· 1 representing all particles spin up and |Ψb 〉=|0··· 0 representing all particles spin down, while the phase transition point is an isolated intermediate-coupling point where√ the two phases coexist equally, which is2 described by the so-called N-qubit maximally entangled GHZ state |Ψpt =√2/2(|1··· 1 +|0··· 0). At the critical point,2the physical quantities including the entanglement are not discontinuous and the matrix product system has longrange correlation and N-qubit maximal entanglement. We believe that our work is helpful for having a comprehensive understanding of quantum phase transitions in matrix product states of one-dimensional spin chains and of potential directive significance to the preparation and control of one-dimensional spin lattice models with stable coherence and N-qubit maximal entanglement.
基金This work has been partially supported by the Ministerio de Ciencia e Innovación(Spain)under projects number FIS2017-88410-P,PID2019-104002GB-C21 and PID2019-104002GB-C22,by the Consejería de Economía,Conocimiento,Empresas y Universidad de la Junta de Andalucía(Spain)under Group FQM-160(JMA)and FQM-370(JEGR),by the European Regional Development Fund(ERDF),ref.SOMM17/6105/UGR,and by the European Commission,ref.H2020-INFRAIA-2014-2015(ENSAR2).Resources supporting this work were provided by the CEAFMC and the Universidad de Huelva High Performance Computer(HPC@UHU)funded by ERDF/MINECO project UNHU-15CE-2848。
文摘The atomic mass table presents zones where the structure of the states changes rapidly as a function of the neutron or proton number.Among them,notable examples are the A≈100 Zr region,the Pb region around the neutron midshell(N=104),and the N≈90 rare-earth region.The observed phenomena can be understood in terms of either shape coexistence or quantum phase transitions.The objective of this study is to find an observable that can distinguish between both shape coexistence and quantum phase transitions.As an observable to be analyzed,we selected the two-neutron transfer intensity between the 0+states in the parent and daughter nuclei.The framework used for this study is the Interacting Boson Model(IBM),including its version with configuration mixing(IBM-CM).To generate wave functions of isotope chains of interest needed for calculating transfer intensities,previous systematic studies using IBM and IBM-CM were used without changing the parameters.The results of two-neutron transfer intensities are presented for Zr,Hg,and Pt isotopic chains using IBM-CM.Moreover,for Zr,Pt,and Sm isotopic chains,the results are presented using IBM with only a single configuration,i.e.,without using configuration mixing.For Zr,the two-neutron transfer intensities between the ground states provide a clear observable,indicating that normal and intruder configurations coexist in the low-lying spectrum and cross at A=98→100.This can help clarify whether shape coexistence induces a given quantum phase transition.For Pt,in which shape coexistence is present and the regular and intruder configurations cross for the ground state,there is almost no impact on the value of the two-neutron transfer intensity.Similar is the situation with Hg,where the ground state always has a regular nature.For the Sm isotope chain,which is one of the quantum phase transition paradigms,the value of the two-neutron transfer intensity is affected strongly.
基金the support from the RGC of Hong Kong SAR China (Grant Nos. GRF 17303019 and 17301420)the National Key Research and Development Program of China (Grant No. 2016YFA0300502)+3 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No. XDB33000000)support from the National Natural Science Foundation of China (Grant No. 12004020)AWS was supported by the NSF (Grant No. DMR-1710170)by the Simons Foundation (Grant No. 511064)。
文摘Recent experiments [Guo et al., Phys. Rev. Lett. 124 206602(2020)] on thermodynamic properties of the frustrated layered quantum magnet SrCu_(2)(BO_(3))_(2)-the Shastry–Sutherland material-have provided strong evidence for a lowtemperature phase transition between plaquette-singlet and antiferromagnetic order as a function of pressure. Further motivated by the recently discovered unusual first-order quantum phase transition with an apparent emergent O(4) symmetry of the antiferromagnetic and plaquette-singlet order parameters in a two-dimensional "checkerboard J-Q" quantum spin model[Zhao et al., Nat. Phys. 15 678(2019)], we here study the same model in the presence of weak inter-layer couplings. Our focus is on the evolution of the emergent symmetry as the system crosses over from two to three dimensions and the phase transition extends from strictly zero temperature in two dimensions up to finite temperature as expected in SrCu_(2)(BO_(3))_(2).Using quantum Monte Carlo simulations, we map out the phase boundaries of the plaquette-singlet and antiferromagnetic phases, with particular focus on the triple point where these two ordered phases meet the paramagnetic phase for given strength of the inter-layer coupling. All transitions are first-order in the neighborhood of the triple point. We show that the emergent O(4) symmetry of the coexistence state breaks down clearly when the interlayer coupling becomes sufficiently large, but for a weak coupling, of the magnitude expected experimentally, the enlarged symmetry can still be observed at the triple point up to significant length scales. Thus, it is likely that the plaquette-singlet to antiferromagnetic transition in SrCu_(2)(BO_(3))_(2) exhibits remnants of emergent O(4) symmetry, which should be observable due to additional weakly gapped Goldstone modes.
基金Project supported by the NSF under Grant No.DMR-1710170 and by a Simons Investigator Grant.
文摘We use quantum Monte Carlo simulations to study an S = 1/2 spin model with competing multi-spin interactions. We find a quantum phase transition between a columnar valence-bond solid(cVBS) and a Néel antiferromagnet(AFM), as in the scenario of deconfined quantum-critical points, as well as a transition between the AFM and a staggered valence-bond solid(sVBS). By continuously varying a parameter, the sVBS–AFM and AFM–cVBS boundaries merge into a direct sVBS–cVBS transition. Unlike previous models with putative deconfined AFM–cVBS transitions, e.g., the standard J–Q model,in our extended J–Q model with competing cVBS and sVBS inducing terms the transition can be tuned from continuous to first-order. We find the expected emergent U(1) symmetry of the microscopically Z4 symmetric cVBS order parameter when the transition is continuous. In contrast, when the transition changes to first-order, the clock-like Z4 fluctuations are absent and there is no emergent higher symmetry. We argue that the confined spinons in the sVBS phase are fracton-like.We also present results for an SU(3) symmetric model with a similar phase diagram. The new family of models can serve as a useful tool for further investigating open questions related to deconfined quantum criticality and its associated emergent symmetries.
基金the National Natural Science Foundation of China(Grant No.11805285)Natural Science Foundation of Chongqing of China(Grant No.cstc2020jcyjmsxmX0034)the Science and Technology Research Program of Chongqing Municipal Education Commission(Grant No.KJQN 201900703)。
文摘We investigate quantum phase transitions for q-state quantum Potts models(q=2,3,4)on a square lattice and for the Ising model on a honeycomb lattice by using the infinite projected entangled-pair state algorithm with a simplified updating scheme.We extend the universal order parameter to a two-dimensional lattice system,which allows us to explore quantum phase transitions with symmetry-broken order for any translation-invariant quantum lattice system of the symmetry group G.The universal order parameter is zero in the symmetric phase,and it ranges from zero to unity in the symmetry-broken phase.The ground-state fidelity per lattice site is computed,and a pinch point is identified on the fidelity surface near the critical point.The results offer another example highlighting the connection between(i)critical points for a quantum many-body system undergoing a quantum phase-transition and(ii)pinch points on a fidelity surface.In addition,we discuss three quantum coherence measures:the quantum Jensen–Shannon divergence,the relative entropy of coherence,and the l1norm of coherence,which are singular at the critical point,thereby identifying quantum phase transitions.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10774088)the Key Program of the National Natural Science Foundation of China (Grant No. 10534030)
文摘In this paper, we study the quantum phase transition and the effect of impurity on the thermal entanglement between any two lattices in three-qubit Heisenberg XX chain in a uniform magnetic field. We show that the quantum phase transition always appears when impurity parameter is an arbitrary constant and unequal to zero, the external magnetic field and impurity parameters have a great effect on it. Also, there exists a relation between the quantum phase transition and the entanglement. By modulating the temperature, magnetic field and the impurity parameters, the entanglement between any two lattices can exhibit platform-like behaviour, which can be used to realize entanglement switch.