Finding the common origin of non-Fermi liquids(NFLs) transport in high-temperature superconductors(HTSCs)has proven to be fundamentally challenging due to the prominence of various collective fluctuations.Here,we prop...Finding the common origin of non-Fermi liquids(NFLs) transport in high-temperature superconductors(HTSCs)has proven to be fundamentally challenging due to the prominence of various collective fluctuations.Here,we propose a comprehensive non-Hermitian Hamiltonian(NHH) for quantum coupling of multiple scattering mechanisms associated with four types of order fluctuations.It predicts that the anticommutation symmetry of the spinor fermions constrains the scattering rate to a unified quadrature scaling,i.e.,Γ=Γ_(1)+√Γ_(Q)^(2)+(μk_(B)T)^(2)+(vμ_(B)B)^(2)+(γ_(E)E)^(2).This scaling yields a comprehensive and accurate description of two widespread NFL behaviors in HTSCs,i.e.,a temperature-scaling crossover between quadratic and linear laws and the quadrature magnetoresistance,validated by several dozens of data sets for broad phase regimes.It reveals that the common origin of these behaviors is the spinor-symmetry-constrained quantum coupling of spin-wave and topological excitations of mesoscopic orders.Finally,we show that this NHH can be easily extended to other complex quantum fluids by specifying the corresponding symmetries.It is concluded that this work uncovers a critical organization principle(i.e.,the spinor symmetry) underlying the NFL transport,thus providing a novel theoretical framework to advance the transport theory of correlated electron systems.展开更多
We investigate a modified Anderson model at the large-N limit,where the Coulomb interaction is replaced by the Sachdev-Ye-Kitaev random interaction.The resistivity of conduction electron ρ_(c) has a minimum value aro...We investigate a modified Anderson model at the large-N limit,where the Coulomb interaction is replaced by the Sachdev-Ye-Kitaev random interaction.The resistivity of conduction electron ρ_(c) has a minimum value around temperature T^(*),which is similar to the Kondo system,but the impurity electron’s density of state A_(d)(ω) demonstrates no sharp-peak like the Kondo resonance around the Fermi surface.This provides a counterintuitive example where resistivity minimum exists without Kondo resonance.The impurity electron’s entropy S_(d) and specific heat capacity C_(v) show a crossover from Fermi liquid to a non-Fermi liquid behavior dependent on temperature.The system is a Fermi liquid at T T^(*),and then becomes a Fermi gas at sufficiently high temperatures T>>T^(*).The non-Fermi liquid at the intermediate-T regime does not occur in the standard Anderson model.We also make a renormalization group analysis,which confirms the crossover from Fermi liquid to the non-Fermi behavior.It is emphasized that the resistivity minimum emerges in our model when the system behaves as a non-Fermi liquid rather than Fermi liquid,which provides an alternative example showing resistivity minimum in condensed matter physics.展开更多
The effects of interchannel scattering of conduction electrons by the impu rity and repulsion of conduction electrons at the impurity site on the two-channel Kondo model are simultaneously considered in this paper.It ...The effects of interchannel scattering of conduction electrons by the impu rity and repulsion of conduction electrons at the impurity site on the two-channel Kondo model are simultaneously considered in this paper.It is shown that these two perturbations will substantially modify the usual local non-Fermi liquid behavior of the two-channel Kondo model.With bosonization and unitary transformations we find that the system can be transformed into a single channel Kondo model with anisotropy between longitudinal and transverse exchange couplings.Whatever for originally antiferromagnetic or ferromagnetic isotropic coupling,the system always flows to strong-coupling limit,which exhibits local Fermi liquid behavior at low temperatures.展开更多
Recasting the BCS theory in the larger framework of the Bethe-Salpeter equation, a new equation is derived for the temperature-dependent critical current density jc(T) of an elemental superconductor (SC) directly in t...Recasting the BCS theory in the larger framework of the Bethe-Salpeter equation, a new equation is derived for the temperature-dependent critical current density jc(T) of an elemental superconductor (SC) directly in terms of the basic parameters of the theory, namely the dimensionless coupling constant [N(0)V], the Debye temperature θD and, additionally, the Fermi energy EF—unlike earlier such equations based on diverse, indirect criteria. Our approach provides an ab initio theoretical justification for one of the latter, text book equations invoked at T = 0 which involves Fermi momentum;additionally, it relates jc with the relevant parameters of the problem at T ≠ 0. Noting that the numerical value of EF of a high-Tc SC is a necessary input for the construction of its Fermi surface—which sheds light on its gap-structure, we also briefly discuss extension of our approach for such SCs.展开更多
It is well known that the critical current density of a superconductor depends on its size, shape, nature of doping and the manner of preparation. It is suggested here that the collective effect of such differences fo...It is well known that the critical current density of a superconductor depends on its size, shape, nature of doping and the manner of preparation. It is suggested here that the collective effect of such differences for different samples of the same superconductor is to endow them with different values of the Fermi energy—a single property to which may be attributed the observed variation in their critical current densities. The study reported here extends our earlier work concerned with the generalized BCS equations [Malik, G.P. (2010) Physica B, 405, 3475-3481;Malik, G.P. (2013) WJCMP, 3,103-110]. We develop here for the first time a framework of microscopic equations that incorporates all of the following parameters of a superconductor: temperature, momentum of Cooper pairs, Fermi energy, applied magnetic field and critical current density. As an application of this framework, we address the different values of critical current densities of Bi-2212 for non-zero values of temperature and applied magnetic field that have been reported in the literature.展开更多
Chemical properties of seawater are studied at forced shifting of Fermi level εF? in the band gap of liquid water due to deviation of its composition H2O1−z ( |?z|−13 ) from the stoichiometric one...Chemical properties of seawater are studied at forced shifting of Fermi level εF? in the band gap of liquid water due to deviation of its composition H2O1−z ( |?z|−13 ) from the stoichiometric one ( z = 0 ). It is shown that the hypo-stoichiometric state ( z > 0 ) of seawater emerges when Fermi level is shifted to the local electron level ?εH3O of hydroxonium H3O+ in galvanic cell with the strongly polarized anode and the quasi-equilibrium cathode. Then, each εH3O is occupied by electron and hydroxonium radicals [H3O]? together with hydroxide anions [OH−]?form in seawater hydrated electrons [(H2O)2−] . The opposite hyper-stoichiometric state ( z εOH for removing electron from each hydroxide ion OH−and forming hydroxyl radicals [OH] as strong oxidizers. It turned out that the ions of sodium and chlorine are connected into hydrates of sodium hypochlorite NaClO in this case.展开更多
In unconventional superconductors, it is generally believed that understanding the physical properties of the normal state is a pre-requisite for understanding the superconductivity mechanism. In conventional supercon...In unconventional superconductors, it is generally believed that understanding the physical properties of the normal state is a pre-requisite for understanding the superconductivity mechanism. In conventional superconductors like niobium or lead, the normal state is a Fermi liquid with a well-defined Fermi surface and well-defined quasipartcles along the Fermi surface. Superconductivity is realized in this case by the Fermi surface instability in the superconducting state and the formation and condensation of the electron pairs(Cooper pairing). The high temperature cuprate superconductors, on the other hand, represent another extreme case that superconductivity can be realized in the underdoped region where there is neither well-defined Fermi surface due to the pseudogap formation nor quasiparticles near the antinodal regions in the normal state. Here we report a novel scenario that superconductivity is realized in a system with well-defined Fermi surface but without quasiparticles along the Fermi surface in the normal state.High resolution laser-based angle-resolved photoemission measurements have been performed on an optimally-doped iron-based superconductor(Ba_(0.6)K_(0.4))Fe_2As_2. We find that, while sharp superconducting coherence peaks emerge in the superconducting state on the hole-like Fermi surface sheets, no quasiparticle peak is present in the normal state. Its electronic behaviours deviate strongly from a Fermi liquid system. The superconducting gap of such a system exhibits an unusual temperature dependence that it is nearly a constant in the superconducting state and abruptly closes at Tc. These observations have provided a new platform to study unconventional superconductivity in a non-Fermi liquid system.展开更多
We reveal and explain the scaling behavior of the thermopower S/T exhibited by the archetypal heavy-fermion （HF） metal YbRh2Si2 under the application of magnetic field B at temperature T. We show that the same scali...We reveal and explain the scaling behavior of the thermopower S/T exhibited by the archetypal heavy-fermion （HF） metal YbRh2Si2 under the application of magnetic field B at temperature T. We show that the same scaling is demonstrated by different HF compounds such as/3-YbA1B4 and the strongly correlated layered cobalt oxide [BiBa0.66K0.3602]CoO2. Using YbRh2Si2 as an example, we demonstrate that the scaling behavior of SIT is violated at the antiferromagnetic phase transition, while both the residual resistivity Po and the density of states, N, experience jumps at the phase transition, causing the thermopower to make two jumps and change its sign. Our elucidation is based on flattening of the single-particle spectrum that profoundly affects Po and N. To depict the main features of the SIT behavior, we construct a T-B schematic phase diagram of YbRh2Si2. Our calculated SIT for the HF compounds are in good agreement with experimental facts and support our observations.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 91952201 and 11452002)。
文摘Finding the common origin of non-Fermi liquids(NFLs) transport in high-temperature superconductors(HTSCs)has proven to be fundamentally challenging due to the prominence of various collective fluctuations.Here,we propose a comprehensive non-Hermitian Hamiltonian(NHH) for quantum coupling of multiple scattering mechanisms associated with four types of order fluctuations.It predicts that the anticommutation symmetry of the spinor fermions constrains the scattering rate to a unified quadrature scaling,i.e.,Γ=Γ_(1)+√Γ_(Q)^(2)+(μk_(B)T)^(2)+(vμ_(B)B)^(2)+(γ_(E)E)^(2).This scaling yields a comprehensive and accurate description of two widespread NFL behaviors in HTSCs,i.e.,a temperature-scaling crossover between quadratic and linear laws and the quadrature magnetoresistance,validated by several dozens of data sets for broad phase regimes.It reveals that the common origin of these behaviors is the spinor-symmetry-constrained quantum coupling of spin-wave and topological excitations of mesoscopic orders.Finally,we show that this NHH can be easily extended to other complex quantum fluids by specifying the corresponding symmetries.It is concluded that this work uncovers a critical organization principle(i.e.,the spinor symmetry) underlying the NFL transport,thus providing a novel theoretical framework to advance the transport theory of correlated electron systems.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674139,11704166,and 11834005)the Fundamental Research Funds for the Central Universities,China,and PCSIRT(Grant No.IRT-16R35)。
文摘We investigate a modified Anderson model at the large-N limit,where the Coulomb interaction is replaced by the Sachdev-Ye-Kitaev random interaction.The resistivity of conduction electron ρ_(c) has a minimum value around temperature T^(*),which is similar to the Kondo system,but the impurity electron’s density of state A_(d)(ω) demonstrates no sharp-peak like the Kondo resonance around the Fermi surface.This provides a counterintuitive example where resistivity minimum exists without Kondo resonance.The impurity electron’s entropy S_(d) and specific heat capacity C_(v) show a crossover from Fermi liquid to a non-Fermi liquid behavior dependent on temperature.The system is a Fermi liquid at T T^(*),and then becomes a Fermi gas at sufficiently high temperatures T>>T^(*).The non-Fermi liquid at the intermediate-T regime does not occur in the standard Anderson model.We also make a renormalization group analysis,which confirms the crossover from Fermi liquid to the non-Fermi behavior.It is emphasized that the resistivity minimum emerges in our model when the system behaves as a non-Fermi liquid rather than Fermi liquid,which provides an alternative example showing resistivity minimum in condensed matter physics.
文摘The effects of interchannel scattering of conduction electrons by the impu rity and repulsion of conduction electrons at the impurity site on the two-channel Kondo model are simultaneously considered in this paper.It is shown that these two perturbations will substantially modify the usual local non-Fermi liquid behavior of the two-channel Kondo model.With bosonization and unitary transformations we find that the system can be transformed into a single channel Kondo model with anisotropy between longitudinal and transverse exchange couplings.Whatever for originally antiferromagnetic or ferromagnetic isotropic coupling,the system always flows to strong-coupling limit,which exhibits local Fermi liquid behavior at low temperatures.
文摘Recasting the BCS theory in the larger framework of the Bethe-Salpeter equation, a new equation is derived for the temperature-dependent critical current density jc(T) of an elemental superconductor (SC) directly in terms of the basic parameters of the theory, namely the dimensionless coupling constant [N(0)V], the Debye temperature θD and, additionally, the Fermi energy EF—unlike earlier such equations based on diverse, indirect criteria. Our approach provides an ab initio theoretical justification for one of the latter, text book equations invoked at T = 0 which involves Fermi momentum;additionally, it relates jc with the relevant parameters of the problem at T ≠ 0. Noting that the numerical value of EF of a high-Tc SC is a necessary input for the construction of its Fermi surface—which sheds light on its gap-structure, we also briefly discuss extension of our approach for such SCs.
文摘It is well known that the critical current density of a superconductor depends on its size, shape, nature of doping and the manner of preparation. It is suggested here that the collective effect of such differences for different samples of the same superconductor is to endow them with different values of the Fermi energy—a single property to which may be attributed the observed variation in their critical current densities. The study reported here extends our earlier work concerned with the generalized BCS equations [Malik, G.P. (2010) Physica B, 405, 3475-3481;Malik, G.P. (2013) WJCMP, 3,103-110]. We develop here for the first time a framework of microscopic equations that incorporates all of the following parameters of a superconductor: temperature, momentum of Cooper pairs, Fermi energy, applied magnetic field and critical current density. As an application of this framework, we address the different values of critical current densities of Bi-2212 for non-zero values of temperature and applied magnetic field that have been reported in the literature.
文摘Chemical properties of seawater are studied at forced shifting of Fermi level εF? in the band gap of liquid water due to deviation of its composition H2O1−z ( |?z|−13 ) from the stoichiometric one ( z = 0 ). It is shown that the hypo-stoichiometric state ( z > 0 ) of seawater emerges when Fermi level is shifted to the local electron level ?εH3O of hydroxonium H3O+ in galvanic cell with the strongly polarized anode and the quasi-equilibrium cathode. Then, each εH3O is occupied by electron and hydroxonium radicals [H3O]? together with hydroxide anions [OH−]?form in seawater hydrated electrons [(H2O)2−] . The opposite hyper-stoichiometric state ( z εOH for removing electron from each hydroxide ion OH−and forming hydroxyl radicals [OH] as strong oxidizers. It turned out that the ions of sodium and chlorine are connected into hydrates of sodium hypochlorite NaClO in this case.
基金supported by the National Key Research and Development Program of China (2016YFA0300300 and 2017YFA0302900)the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (XDB07020300 and XDB25000000)+1 种基金the National Basic Research Program of China (2015CB921000), the National Natural Science Foundation of China (11334010)and the Youth Innovation Promotion Association of CAS (2017013)
文摘In unconventional superconductors, it is generally believed that understanding the physical properties of the normal state is a pre-requisite for understanding the superconductivity mechanism. In conventional superconductors like niobium or lead, the normal state is a Fermi liquid with a well-defined Fermi surface and well-defined quasipartcles along the Fermi surface. Superconductivity is realized in this case by the Fermi surface instability in the superconducting state and the formation and condensation of the electron pairs(Cooper pairing). The high temperature cuprate superconductors, on the other hand, represent another extreme case that superconductivity can be realized in the underdoped region where there is neither well-defined Fermi surface due to the pseudogap formation nor quasiparticles near the antinodal regions in the normal state. Here we report a novel scenario that superconductivity is realized in a system with well-defined Fermi surface but without quasiparticles along the Fermi surface in the normal state.High resolution laser-based angle-resolved photoemission measurements have been performed on an optimally-doped iron-based superconductor(Ba_(0.6)K_(0.4))Fe_2As_2. We find that, while sharp superconducting coherence peaks emerge in the superconducting state on the hole-like Fermi surface sheets, no quasiparticle peak is present in the normal state. Its electronic behaviours deviate strongly from a Fermi liquid system. The superconducting gap of such a system exhibits an unusual temperature dependence that it is nearly a constant in the superconducting state and abruptly closes at Tc. These observations have provided a new platform to study unconventional superconductivity in a non-Fermi liquid system.
文摘We reveal and explain the scaling behavior of the thermopower S/T exhibited by the archetypal heavy-fermion （HF） metal YbRh2Si2 under the application of magnetic field B at temperature T. We show that the same scaling is demonstrated by different HF compounds such as/3-YbA1B4 and the strongly correlated layered cobalt oxide [BiBa0.66K0.3602]CoO2. Using YbRh2Si2 as an example, we demonstrate that the scaling behavior of SIT is violated at the antiferromagnetic phase transition, while both the residual resistivity Po and the density of states, N, experience jumps at the phase transition, causing the thermopower to make two jumps and change its sign. Our elucidation is based on flattening of the single-particle spectrum that profoundly affects Po and N. To depict the main features of the SIT behavior, we construct a T-B schematic phase diagram of YbRh2Si2. Our calculated SIT for the HF compounds are in good agreement with experimental facts and support our observations.
