We investigate the existence and stability of surface defect gap solitons at an interface between a defect in a two-dimensional optical lattice and a uniform saturable Kerr nonlinear medium. The surface defect embedde...We investigate the existence and stability of surface defect gap solitons at an interface between a defect in a two-dimensional optical lattice and a uniform saturable Kerr nonlinear medium. The surface defect embedded in the two-dimensional optical lattice gives rise to some unique properties. It is interestingly found that for the negative defect, stable surface defect gap solitons can exist both in the semi-infinite gap and in the first gap. The deeper the negative defect, the narrower the stable region in the semi-infinite gap will be. For a positive defect, the surface defect gap solitons exist only in the semi-infinite gap and the stable region localizes in a low power region.展开更多
We study the stability of zero-vorticity and vortex lattice quantum droplets(LQDs),which are de-scribed by a two-dimensional(2D)Gross-Pitaevskii(GP)equation with a periodic potential and Lee-Huang-Yang(LHY)term.The LQ...We study the stability of zero-vorticity and vortex lattice quantum droplets(LQDs),which are de-scribed by a two-dimensional(2D)Gross-Pitaevskii(GP)equation with a periodic potential and Lee-Huang-Yang(LHY)term.The LQDs are divided in two types:onsite-centered and offsite-centered LQDs,the centers of which are located at the minimum and the maximum of the potential,respec-tively.The stability areas of these two types of LQDs with diferent number of sites for zero-vorticity and vorticity with S=1 are given.We found that the μ-N relationship of the stable LQDs with a fixed number of sites can violate the Vakhitov-Kolokolov(VK)criterion,which is a necessary stability condition for nonlinear modes with an attractive interaction.Moreover,the μ-N relationship shows that two types of vortex LQDs with the same number of sites are degenerated,while the zero-vorticity LQDs are not degenerated.It is worth mentioning that the offsite-centered LQDs with zero-vorticity and vortex LQDs with S=1 are heterogeneous.展开更多
We study the possibility of stabilizing a Fulde-Ferrell-Larkin-Ovchinnikov(FFLO)state in an equally populated two-component Fermi gas trapped in a moving two-dimensional optical lattice.For a system with nearly half f...We study the possibility of stabilizing a Fulde-Ferrell-Larkin-Ovchinnikov(FFLO)state in an equally populated two-component Fermi gas trapped in a moving two-dimensional optical lattice.For a system with nearly half filling,we find that a finite pairing momentum perpendicular to the moving direction can be spontaneously induced for a proper choice of lattice velocity.As a result,the total pairing momentum is tilted towards the nesting vector to take advantage of the significant enhancement of the density of states.展开更多
We construct a power enhancement cavity to form an optical lattice in an ytterbium optical clock.It is demonstrated that the intra-cavity lattice power can be increased by about 45 times,and the trap depth can be as l...We construct a power enhancement cavity to form an optical lattice in an ytterbium optical clock.It is demonstrated that the intra-cavity lattice power can be increased by about 45 times,and the trap depth can be as large as 1400Er when laser light with a power of only 0.6 W incident to the lattice cavity.Such high trap depths are the key to accurate evaluation of the lattice-induced light shift with an uncertainty down to~1×10-18.By probing the ytterbium atoms trapped in the power-enhanced optical lattice,we obtain a 4.3 Hz-linewidth Rabi spectrum,which is then used to feedback to the clock laser for the close loop operation of the optical lattice clock.We evaluate the density shift of the Yb optical lattice clock based on interleaving measurements,which is-0.46(62)mHz.This result is smaller compared to the density shift of our first Yb optical clock without lattice power enhancement cavity mainly due to a larger lattice diameter of 344μm.展开更多
Moirésuperlattices,a twisted functional structure crossing the periodic and nonperiodic potentials,have recently attracted great interest in multidisciplinary fields,including optics and ultracold atoms,because o...Moirésuperlattices,a twisted functional structure crossing the periodic and nonperiodic potentials,have recently attracted great interest in multidisciplinary fields,including optics and ultracold atoms,because of their unique band structures,physical properties,and potential implications.Driven by recent experiments on quantum phenomena of bosonic gases,the atomic Bose–Einstein condensates in moiréoptical lattices,by which other quantum gases such as ultracold fermionic atoms are trapped,could be readily achieved in ultracold atom laboratories,whereas the associated nonlinear localization mechanism remains unexploited.Here,we report the nonlinear localization theory of ultracold atomic Fermi gases in two-dimensional moiréoptical lattices.The linear Bloch-wave spectrum of such a twisted structure exhibits rich nontrivial flat bands,which are separated by different finite bandgaps wherein the existence,properties,and dynamics of localized superfluid Fermi gas structures of two types,gap solitons and gap vortices(topological modes)with vortex charge S¼1,are studied numerically.Our results demonstrate the wide stability regions and robustness of these localized structures,opening up a new avenue for studying soliton physics and moiréphysics in ultracold atoms beyond bosonic gases.展开更多
We report the 87Sr optical lattice clock developed at the National Time Service Center. We achieved a closed-loop operation of the optical lattice clock based on 87Sr atoms. The linewidth of the spin-polarized clock p...We report the 87Sr optical lattice clock developed at the National Time Service Center. We achieved a closed-loop operation of the optical lattice clock based on 87Sr atoms. The linewidth of the spin-polarized clock peak is 3.9 Hz with a clock laser pulse length of 300 ms, which corresponds to a Fourier-limited linewidth of 3 Hz. The fitting of the in-loop error signal data shows that the instability is approximately 5 × 10 15τ-1/2, affected primarily by the white noise. The fractional frequency difference averages down to 5.7 × 10 ^-17 for an averaging time of 3000 s.展开更多
We report a transportable one-dimensional optical lattice clock based on 87Sr at the National Time Service Center.The transportable apparatus consists of a compact vacuum system and compact optical subsystems.The vacu...We report a transportable one-dimensional optical lattice clock based on 87Sr at the National Time Service Center.The transportable apparatus consists of a compact vacuum system and compact optical subsystems.The vacuum system with a size of 90 cm×20 cm×42 cm and the beam distributors are assembled on a double-layer optical breadboard.The modularized optical subsystems are integrated on independent optical breadboards.By using a 230 ms clock laser pulse,spin-polarized spectroscopy with a linewidth of 4.8 Hz is obtained which is close to the 3.9 Hz Fourier-limit linewidth.The time interleaved self-comparison frequency instability is determined to be 6.3 × 10^-17 at an averaging time of 2000 s.展开更多
An optical atomic clock with 171yb atoms is devised and tested. By using a two-stage Doppler cooling technique, the 171Yb atoms are cooled down to a temperature of 6 ± 3 μK, which is close to the Doppler limit. ...An optical atomic clock with 171yb atoms is devised and tested. By using a two-stage Doppler cooling technique, the 171Yb atoms are cooled down to a temperature of 6 ± 3 μK, which is close to the Doppler limit. Then, the cold 171Yb atoms are loaded into a one-dimensional optical lattice with a wavelength of 759 nm in the Lamb-Dicke regime. Furthermore, these cold 171yb atoms are excited from the ground-state 1S0 to the excited-state 3P0 by a clock laser with a wavelength of 578 nm. Finally, the 1S0-3P0 clock-transition spectrum of these 171yb atoms is obtained by measuring the dependence of the population of the ground-state 1 S0 upon the clock-laser detuning.展开更多
The nonlinear Landau Zener tunneling and nonlinear Rabi oscillations of Bose-Einstein condensate (BEC) with higher-order atomic interaction between the Bloch bands in an accelerating optical lattice are discussed. W...The nonlinear Landau Zener tunneling and nonlinear Rabi oscillations of Bose-Einstein condensate (BEC) with higher-order atomic interaction between the Bloch bands in an accelerating optical lattice are discussed. Within the two-level model, the tunneling probability of BEC with higher-order atomic interaction between Bloch bands is obtained. We finds that the tunneling rate is closely related to the higher-order atomic interaction. Furthermore, the nonlinear Rabi oscillations of BEC with higher-order atomic interaction between the bands are discussed by imposing a periodic modulation on the level bias. Analytical expressions of the critical higher-order atomic interaction for suppressing/enhancing the Rabi oscillations are obtained. It is shown that the critical value strongly depends on the modulation parameters (i.e., the modulation amplitude and frequency) and the strength of periodic potential.展开更多
An optical lattice clock based on 87Sr is built at National Institute of Metrology (NIM) of China. The systematic frequency shifts of the clock are evaluated with a total uncertainty of 2.3×10-16. To measure it...An optical lattice clock based on 87Sr is built at National Institute of Metrology (NIM) of China. The systematic frequency shifts of the clock are evaluated with a total uncertainty of 2.3×10-16. To measure its absolute frequency with respect to NIM's cesium fountain clock NIM5, the frequency of a flywheel H-maser of NIM5 is transferred to the Sr laboratory through a 50-kin-long fiber. reference frequency of this H-maser, is used for the optical this Sr clock is measured to be 429228004229873.7(1.4)Hz. A fiber optical frequency comb, phase-locked to the frequency measurement. The absolute frequency of展开更多
We report on the magic wavelength measurement of our optical lattice clock based on fermion strontium atoms at the National Institute of Metrology (NIM). A Ti:sapphire solid state laser locked to a reference cavity...We report on the magic wavelength measurement of our optical lattice clock based on fermion strontium atoms at the National Institute of Metrology (NIM). A Ti:sapphire solid state laser locked to a reference cavity inside a temperature-stabilized vacuum chamber is employed to generate the optical lattice. The laser frequency is measured by an erbium fiber frequency comb. The trap depth is modulated by varying the lattice laser power via an acousto-optic modulator. We obtain the frequency shift coefficient at this lattice wavelength by measuring the diffbrential frequency shift of the clock transition of the strontium atoms at different trap depths, and the frequency shift coefficient at this lattice wavelength is obtained. We measure the frequency shift coefficients at different lattice frequencies around the magic wavelength and linearly fit the measurement data, and the magic wavelength is calculated to be 368554672(44)MHz.展开更多
Recently, the concept of topological insulators has been generalized to topological semimetals, including three-dimensional (3D) Weyl semimetals, 3D Dirac semimetMs, and 3D node-line semimetals (NLSs). In particul...Recently, the concept of topological insulators has been generalized to topological semimetals, including three-dimensional (3D) Weyl semimetals, 3D Dirac semimetMs, and 3D node-line semimetals (NLSs). In particular, several compounds (e.g., certain 3D graphene networks, Cu3PdN, Ca3P2 ) were discovered to be 3D NLSs, in which the conduction and valence bands cross at closed lines in the Brillouin zone. Except for the two-dimensional (2D) Dirac semimetal (e.g., graphene), 2D topological semimetals are much less investigated. Here we propose a new concept of a 2D NLS and suggest that this state could be realized in a new mixed lattice (named as HK lattice) composed by Kagome and honeycomb lattices. It is found that A3B2 (A is a group-liB cation and B is a group-VA anion) compounds (such as Hg3As2) with the HK lattice are 2D NLSs due to the band inversion between the cation Hg-s orbital and the anion As-pz orbital with respect to the mirror symmetry. Since the band inversion occurs between two bands with the same parity, this peculiar 2D NLS could be used as transparent conductors. In the presence of buckling or spin-orbit coupling, the 2D NLS state may turn into a 2D Dirac semimetal state or a 2D topological crystalline insulating state. Since the band gap opening due to buckling or spin-orbit coupling is small, Hg3As3 with the HK lattice can still be regarded as a 2D NLS at room temperature. Our work suggests a new route to design topological materials without involving states with opposite parities.展开更多
This paper proposes a flexible scheme to form various optical multi-well traps for cold atoms or molecules by using a simple optical system composed of an compounded amplitude cosine-only grating and a single lens ill...This paper proposes a flexible scheme to form various optical multi-well traps for cold atoms or molecules by using a simple optical system composed of an compounded amplitude cosine-only grating and a single lens illuminated by a plane light wave or a Gaussian beam. Dynamic manipulation and evolution of multi-well trap can be easily implemented by controlling the modulation frequency of the cosine patterns. It also discusses how to expand this multi-well trap to two-dimensional lattices with single- or multi-well trap by using an orthogonally or non-orthogonally modulated grating, as well as using incoherent multi-beam illumination, and these results show that all the symmetric structures of two-dimensional Bravais lattices can be obtained facilely by using proposed scheme.展开更多
Using the direct perturbation technique, this paper obtains a general perturbed solution of the Bose-Einstein condensates trapped in one-dimensional tilted optical lattice potential. We also gave out two necessary and...Using the direct perturbation technique, this paper obtains a general perturbed solution of the Bose-Einstein condensates trapped in one-dimensional tilted optical lattice potential. We also gave out two necessary and sufficient conditions for boundedness of the perturbed solution. Theoretical analytical results and the corresponding numerical results show that the perturbed solution of the Bose-Einstein condensate system is unbounded in general and indicate that the Bose-Einstein condensates are Lyapunov-unstable. However, when the conditions for boundedness of the perturbed solution are satisfied, then the Bose-Einstein condensates are Lyapunov-stable.展开更多
The impurity-induced localization of two-component Bose-Einstein condensates loaded into deep one-dimensional optical lattices is studied both analytically and numerically. It is shown that, the analytical criteria fo...The impurity-induced localization of two-component Bose-Einstein condensates loaded into deep one-dimensional optical lattices is studied both analytically and numerically. It is shown that, the analytical criteria for self-trapping and moving soliton/breather of the primary-component condensate are modified significantly by an admixture of an impurity component (the second component). The realization of the self-trapped state and the moving soliton/breather states of the primary-component becomes more easy with the minor admixture of the impurity-component, even if the two components are partly overlapped.展开更多
We have developed a systematic analytical approach to the study on the dynamic properties of the linear and the nonlinear excitations for quasi-one-dimensional Bose-Einstein condensate trapped in optical lattices. A n...We have developed a systematic analytical approach to the study on the dynamic properties of the linear and the nonlinear excitations for quasi-one-dimensional Bose-Einstein condensate trapped in optical lattices. A novel linear dispersion relation and an algebraic soliton solution of the condensate are derived analytically under consideration of Bose-Einstein condensate with a periodic potential. By analysing the soliton solution, we find that the interatomic interaction strength has an important effect on soliton dynamic properties of Bose-Einstein condensate.展开更多
Properties of the ground-state solitons, which exist in the spin-orbit coupling (SOC) Bose-Einstein condensates (BEC) in the presence of optical lattices, are presented. Results show that several system parameters...Properties of the ground-state solitons, which exist in the spin-orbit coupling (SOC) Bose-Einstein condensates (BEC) in the presence of optical lattices, are presented. Results show that several system parameters, such as SOC strength, lattice depth, and lattice frequency, have important influences on properties of ground state solitons in SOC BEC. By controlling these parameters, structure and spin polarization of the ground-state solitons can be effectively tuned, so ma- nipulation of atoms may be realized.展开更多
The chaotic ratchet effect for Bos-Einstein condensed atoms in an optical lattice is investigated. By using the direct perturbation method we obtain the chaotic solution of the condensed system. Theoretical analysis r...The chaotic ratchet effect for Bos-Einstein condensed atoms in an optical lattice is investigated. By using the direct perturbation method we obtain the chaotic solution of the condensed system. Theoretical analysis reveals that the transport of the condensed atoms in the ratchet potential is a chaotic one, and corresponding numerical results agree well with the theoretical results.展开更多
An improved nonlinear Schrodinger equation different from usual one of spinor Bose-Einstein condensates (BECs) in an optical lattice are obtained by taking into account a nonlinear term in the equation of motion for...An improved nonlinear Schrodinger equation different from usual one of spinor Bose-Einstein condensates (BECs) in an optical lattice are obtained by taking into account a nonlinear term in the equation of motion for probability amplitude of spins carefully. The elliptic function wave solutions of the model are found under specific boundary condition, for example, the two ends of the atomic chain are fixed. In the case of limit the elliptic function wave solutions are reduced into spin-wave-like or solitons.展开更多
Research on two-dimensional(2D) materials and related van der Waals heterostructures(vdWHs) is intense and remains one of the leading topics in condensed matter physics.Lattice vibrations or phonons of a vdWH provide ...Research on two-dimensional(2D) materials and related van der Waals heterostructures(vdWHs) is intense and remains one of the leading topics in condensed matter physics.Lattice vibrations or phonons of a vdWH provide rich information,such as lattice structure,phonon dispersion,electronic band structure and electron–phonon coupling.Here,we provide a mini review on the lattice vibrations in vdWHs probed by Raman spectroscopy.First,we introduced different kinds of vdWHs,including their structures,properties and potential applications.Second,we discussed interlayer and intralayer phonon in twist multilayer graphene and MoS2.The frequencies of interlayer and intralayer modes can be reproduced by linear chain model(LCM)and phonon folding induced by periodical moiré potentials,respectively.Then,we extended LCM to vdWHs formed by distinct 2D materials,such as MoS2/graphene and hBN/WS2 heterostructures.We further demonstrated how to calculate Raman intensity of interlayer modes in vdWHs by interlayer polarizability model.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 11174147)the Natural Science Foundation of Jiangsu Province, China (Grant No. BK2009366)
文摘We investigate the existence and stability of surface defect gap solitons at an interface between a defect in a two-dimensional optical lattice and a uniform saturable Kerr nonlinear medium. The surface defect embedded in the two-dimensional optical lattice gives rise to some unique properties. It is interestingly found that for the negative defect, stable surface defect gap solitons can exist both in the semi-infinite gap and in the first gap. The deeper the negative defect, the narrower the stable region in the semi-infinite gap will be. For a positive defect, the surface defect gap solitons exist only in the semi-infinite gap and the stable region localizes in a low power region.
基金This work was supported by the National Natural Science Foundation of China(NNSFC)through Grant Nos.11905032 and 11874112the Key Research Projects of General Col-leges in Guangdong Province through Grant No.2019KZDXM001+1 种基金the Foundation for Distinguished Young Talents in Higher Educa-tion of Guangdong through Grant No.2018KQNCX279the Special Funds for the Cultivation of Guangdong College Students Scientific and Technological Innovation(No.xsjj202005zra01).
文摘We study the stability of zero-vorticity and vortex lattice quantum droplets(LQDs),which are de-scribed by a two-dimensional(2D)Gross-Pitaevskii(GP)equation with a periodic potential and Lee-Huang-Yang(LHY)term.The LQDs are divided in two types:onsite-centered and offsite-centered LQDs,the centers of which are located at the minimum and the maximum of the potential,respec-tively.The stability areas of these two types of LQDs with diferent number of sites for zero-vorticity and vorticity with S=1 are given.We found that the μ-N relationship of the stable LQDs with a fixed number of sites can violate the Vakhitov-Kolokolov(VK)criterion,which is a necessary stability condition for nonlinear modes with an attractive interaction.Moreover,the μ-N relationship shows that two types of vortex LQDs with the same number of sites are degenerated,while the zero-vorticity LQDs are not degenerated.It is worth mentioning that the offsite-centered LQDs with zero-vorticity and vortex LQDs with S=1 are heterogeneous.
基金supported by the Beijing Natural Science Foundation,China(Grant No.Z180013)the National Natural Science Foundation of China(Grant Nos.11522436,11774425,and 12074428)+1 种基金the National Key R&D Program of China(Grant No.2018YFA0306501)the Research Funds of Renmin University of China(Grant Nos.16XNLQ03 and 18XNLQ15)。
文摘We study the possibility of stabilizing a Fulde-Ferrell-Larkin-Ovchinnikov(FFLO)state in an equally populated two-component Fermi gas trapped in a moving two-dimensional optical lattice.For a system with nearly half filling,we find that a finite pairing momentum perpendicular to the moving direction can be spontaneously induced for a proper choice of lattice velocity.As a result,the total pairing momentum is tilted towards the nesting vector to take advantage of the significant enhancement of the density of states.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12334020 and 11927810)the National Key Research and Development Program of China(Grant No.2022YFB3904001).
文摘We construct a power enhancement cavity to form an optical lattice in an ytterbium optical clock.It is demonstrated that the intra-cavity lattice power can be increased by about 45 times,and the trap depth can be as large as 1400Er when laser light with a power of only 0.6 W incident to the lattice cavity.Such high trap depths are the key to accurate evaluation of the lattice-induced light shift with an uncertainty down to~1×10-18.By probing the ytterbium atoms trapped in the power-enhanced optical lattice,we obtain a 4.3 Hz-linewidth Rabi spectrum,which is then used to feedback to the clock laser for the close loop operation of the optical lattice clock.We evaluate the density shift of the Yb optical lattice clock based on interleaving measurements,which is-0.46(62)mHz.This result is smaller compared to the density shift of our first Yb optical clock without lattice power enhancement cavity mainly due to a larger lattice diameter of 344μm.
基金supported by the National Natural Science Foundation of China(Grant No.12074423)the Young Scholar of Chinese Academy of Sciences in Western China(Grant No.XAB2021YN18)+2 种基金the Provincial Science Fund for Distinguished Young Scholars of Shaanxi(Grant No.2024JC-JCQN-11)the China Postdoctoral Science Foundation(Grant No.2023M733722)the Postdoctoral Fellowship Program of CPSF(Grant No.GZC20232947).
文摘Moirésuperlattices,a twisted functional structure crossing the periodic and nonperiodic potentials,have recently attracted great interest in multidisciplinary fields,including optics and ultracold atoms,because of their unique band structures,physical properties,and potential implications.Driven by recent experiments on quantum phenomena of bosonic gases,the atomic Bose–Einstein condensates in moiréoptical lattices,by which other quantum gases such as ultracold fermionic atoms are trapped,could be readily achieved in ultracold atom laboratories,whereas the associated nonlinear localization mechanism remains unexploited.Here,we report the nonlinear localization theory of ultracold atomic Fermi gases in two-dimensional moiréoptical lattices.The linear Bloch-wave spectrum of such a twisted structure exhibits rich nontrivial flat bands,which are separated by different finite bandgaps wherein the existence,properties,and dynamics of localized superfluid Fermi gas structures of two types,gap solitons and gap vortices(topological modes)with vortex charge S¼1,are studied numerically.Our results demonstrate the wide stability regions and robustness of these localized structures,opening up a new avenue for studying soliton physics and moiréphysics in ultracold atoms beyond bosonic gases.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11474282 and 61775220)the Key Research Project of Frontier Science of the Chinese Academy of Sciences(Grant No.QYZDB-SSW-JSC004)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB21030700)
文摘We report the 87Sr optical lattice clock developed at the National Time Service Center. We achieved a closed-loop operation of the optical lattice clock based on 87Sr atoms. The linewidth of the spin-polarized clock peak is 3.9 Hz with a clock laser pulse length of 300 ms, which corresponds to a Fourier-limited linewidth of 3 Hz. The fitting of the in-loop error signal data shows that the instability is approximately 5 × 10 15τ-1/2, affected primarily by the white noise. The fractional frequency difference averages down to 5.7 × 10 ^-17 for an averaging time of 3000 s.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61775220 and 11803042)the Key Research Project of Frontier Science of the Chinese Academy of Sciences(Grant No.QYZDB-SSW-JSC004)the strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB21030100).
文摘We report a transportable one-dimensional optical lattice clock based on 87Sr at the National Time Service Center.The transportable apparatus consists of a compact vacuum system and compact optical subsystems.The vacuum system with a size of 90 cm×20 cm×42 cm and the beam distributors are assembled on a double-layer optical breadboard.The modularized optical subsystems are integrated on independent optical breadboards.By using a 230 ms clock laser pulse,spin-polarized spectroscopy with a linewidth of 4.8 Hz is obtained which is close to the 3.9 Hz Fourier-limit linewidth.The time interleaved self-comparison frequency instability is determined to be 6.3 × 10^-17 at an averaging time of 2000 s.
基金supported by the National Basic Research Program of China (Grant Nos. 2012CB821302 and 2010CB922903)the National Natural Science Foundation of China (Grant Nos. 11134003 and 10774044)the Shanghai Excellent Academic Leaders Program of China (Grant No. 12XD1402400)
文摘An optical atomic clock with 171yb atoms is devised and tested. By using a two-stage Doppler cooling technique, the 171Yb atoms are cooled down to a temperature of 6 ± 3 μK, which is close to the Doppler limit. Then, the cold 171Yb atoms are loaded into a one-dimensional optical lattice with a wavelength of 759 nm in the Lamb-Dicke regime. Furthermore, these cold 171yb atoms are excited from the ground-state 1S0 to the excited-state 3P0 by a clock laser with a wavelength of 578 nm. Finally, the 1S0-3P0 clock-transition spectrum of these 171yb atoms is obtained by measuring the dependence of the population of the ground-state 1 S0 upon the clock-laser detuning.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10774120 and 10975114)the Natural Science Foundation of Gansu Province of China (Grant No. 1010RJZA012)the Science Foundation for Creation of Scienceand Technology of Northwest Normal University of China (Grant Nos. NWNU-KJCXGC-03-17 and NWNU-KJCXGC-03-48)
文摘The nonlinear Landau Zener tunneling and nonlinear Rabi oscillations of Bose-Einstein condensate (BEC) with higher-order atomic interaction between the Bloch bands in an accelerating optical lattice are discussed. Within the two-level model, the tunneling probability of BEC with higher-order atomic interaction between Bloch bands is obtained. We finds that the tunneling rate is closely related to the higher-order atomic interaction. Furthermore, the nonlinear Rabi oscillations of BEC with higher-order atomic interaction between the bands are discussed by imposing a periodic modulation on the level bias. Analytical expressions of the critical higher-order atomic interaction for suppressing/enhancing the Rabi oscillations are obtained. It is shown that the critical value strongly depends on the modulation parameters (i.e., the modulation amplitude and frequency) and the strength of periodic potential.
基金Supported by the National Natural Science Foundation of China under Grant Nos 91336212 and 91436104
文摘An optical lattice clock based on 87Sr is built at National Institute of Metrology (NIM) of China. The systematic frequency shifts of the clock are evaluated with a total uncertainty of 2.3×10-16. To measure its absolute frequency with respect to NIM's cesium fountain clock NIM5, the frequency of a flywheel H-maser of NIM5 is transferred to the Sr laboratory through a 50-kin-long fiber. reference frequency of this H-maser, is used for the optical this Sr clock is measured to be 429228004229873.7(1.4)Hz. A fiber optical frequency comb, phase-locked to the frequency measurement. The absolute frequency of
基金Supported by the National Natural Science Foundation of China under Grant No 91336212
文摘We report on the magic wavelength measurement of our optical lattice clock based on fermion strontium atoms at the National Institute of Metrology (NIM). A Ti:sapphire solid state laser locked to a reference cavity inside a temperature-stabilized vacuum chamber is employed to generate the optical lattice. The laser frequency is measured by an erbium fiber frequency comb. The trap depth is modulated by varying the lattice laser power via an acousto-optic modulator. We obtain the frequency shift coefficient at this lattice wavelength by measuring the diffbrential frequency shift of the clock transition of the strontium atoms at different trap depths, and the frequency shift coefficient at this lattice wavelength is obtained. We measure the frequency shift coefficients at different lattice frequencies around the magic wavelength and linearly fit the measurement data, and the magic wavelength is calculated to be 368554672(44)MHz.
基金Supported by the National Natural Science Foundation of China under Grant No 11374056the Special Funds for Major State Basic Research under Grant No 2015CB921700+1 种基金the Program for Professor of Special Appointment(Eastern Scholar)the Qing Nian Ba Jian Program,and the Fok Ying Tung Education Foundation
文摘Recently, the concept of topological insulators has been generalized to topological semimetals, including three-dimensional (3D) Weyl semimetals, 3D Dirac semimetMs, and 3D node-line semimetals (NLSs). In particular, several compounds (e.g., certain 3D graphene networks, Cu3PdN, Ca3P2 ) were discovered to be 3D NLSs, in which the conduction and valence bands cross at closed lines in the Brillouin zone. Except for the two-dimensional (2D) Dirac semimetal (e.g., graphene), 2D topological semimetals are much less investigated. Here we propose a new concept of a 2D NLS and suggest that this state could be realized in a new mixed lattice (named as HK lattice) composed by Kagome and honeycomb lattices. It is found that A3B2 (A is a group-liB cation and B is a group-VA anion) compounds (such as Hg3As2) with the HK lattice are 2D NLSs due to the band inversion between the cation Hg-s orbital and the anion As-pz orbital with respect to the mirror symmetry. Since the band inversion occurs between two bands with the same parity, this peculiar 2D NLS could be used as transparent conductors. In the presence of buckling or spin-orbit coupling, the 2D NLS state may turn into a 2D Dirac semimetal state or a 2D topological crystalline insulating state. Since the band gap opening due to buckling or spin-orbit coupling is small, Hg3As3 with the HK lattice can still be regarded as a 2D NLS at room temperature. Our work suggests a new route to design topological materials without involving states with opposite parities.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10434060,10674047 and 10804031)the National Key Basic Research and Development Program of China(Grant No.2006CB921604)+2 种基金the Program for Changjiang Scholar and Innovative Research Team,and Shanghai Leading Academic Discipline Project(Grant No.B408)the Youth Foundation of Jiangxi Educational Committee(Grant No.GJJ09530)the Open Research Fund of State Key Laboratory of Precision Spectroscopy,East China Normal University.
文摘This paper proposes a flexible scheme to form various optical multi-well traps for cold atoms or molecules by using a simple optical system composed of an compounded amplitude cosine-only grating and a single lens illuminated by a plane light wave or a Gaussian beam. Dynamic manipulation and evolution of multi-well trap can be easily implemented by controlling the modulation frequency of the cosine patterns. It also discusses how to expand this multi-well trap to two-dimensional lattices with single- or multi-well trap by using an orthogonally or non-orthogonally modulated grating, as well as using incoherent multi-beam illumination, and these results show that all the symmetric structures of two-dimensional Bravais lattices can be obtained facilely by using proposed scheme.
基金supported by the Natural Science Foundation of Hunan Province of China (Grant No. 10JJ3088)the Key Research Foundation of the Education Bureau of Hunan Province of China (Grant Nos. 08A015 and 10A026)
文摘Using the direct perturbation technique, this paper obtains a general perturbed solution of the Bose-Einstein condensates trapped in one-dimensional tilted optical lattice potential. We also gave out two necessary and sufficient conditions for boundedness of the perturbed solution. Theoretical analytical results and the corresponding numerical results show that the perturbed solution of the Bose-Einstein condensate system is unbounded in general and indicate that the Bose-Einstein condensates are Lyapunov-unstable. However, when the conditions for boundedness of the perturbed solution are satisfied, then the Bose-Einstein condensates are Lyapunov-stable.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.10774120 and 10975114)the Natural Science Foundation of Gansu Province of China (Grant No.1010RJZA012)the Natural Science Foundation of Northwest Normal University of China (Grant No.NWNU-KJCXGC-03-48)
文摘The impurity-induced localization of two-component Bose-Einstein condensates loaded into deep one-dimensional optical lattices is studied both analytically and numerically. It is shown that, the analytical criteria for self-trapping and moving soliton/breather of the primary-component condensate are modified significantly by an admixture of an impurity component (the second component). The realization of the self-trapped state and the moving soliton/breather states of the primary-component becomes more easy with the minor admixture of the impurity-component, even if the two components are partly overlapped.
文摘We have developed a systematic analytical approach to the study on the dynamic properties of the linear and the nonlinear excitations for quasi-one-dimensional Bose-Einstein condensate trapped in optical lattices. A novel linear dispersion relation and an algebraic soliton solution of the condensate are derived analytically under consideration of Bose-Einstein condensate with a periodic potential. By analysing the soliton solution, we find that the interatomic interaction strength has an important effect on soliton dynamic properties of Bose-Einstein condensate.
基金supported by the National Natural Science Foundation of China(Grant Nos.11547007 and 11304024)the Yangtze Youth Fund(Grant No.2016cqn55)the Yangtze Fund for Youth Teams of Science and Technology Innovation(Grant No.2015cqt03)
文摘Properties of the ground-state solitons, which exist in the spin-orbit coupling (SOC) Bose-Einstein condensates (BEC) in the presence of optical lattices, are presented. Results show that several system parameters, such as SOC strength, lattice depth, and lattice frequency, have important influences on properties of ground state solitons in SOC BEC. By controlling these parameters, structure and spin polarization of the ground-state solitons can be effectively tuned, so ma- nipulation of atoms may be realized.
基金the Key Research Foundation of the Education Bureau of Hunan Province of China under Grant No.08A015the Natural Science Foundation of Hunan Province of China under Grant No.06JJ2014 and 04JJ40006the National Natural Science Foundation of China under Grant No.10575034
文摘The chaotic ratchet effect for Bos-Einstein condensed atoms in an optical lattice is investigated. By using the direct perturbation method we obtain the chaotic solution of the condensed system. Theoretical analysis reveals that the transport of the condensed atoms in the ratchet potential is a chaotic one, and corresponding numerical results agree well with the theoretical results.
基金supported by National Natural Science Foundation of China under Grant No.10474022
文摘An improved nonlinear Schrodinger equation different from usual one of spinor Bose-Einstein condensates (BECs) in an optical lattice are obtained by taking into account a nonlinear term in the equation of motion for probability amplitude of spins carefully. The elliptic function wave solutions of the model are found under specific boundary condition, for example, the two ends of the atomic chain are fixed. In the case of limit the elliptic function wave solutions are reduced into spin-wave-like or solitons.
基金the National Key Research and Development Program of China (Grant No.2016YFA0301204)the National Natural Science Foundation of China (Grant Nos.11874350 and 11434010)
文摘Research on two-dimensional(2D) materials and related van der Waals heterostructures(vdWHs) is intense and remains one of the leading topics in condensed matter physics.Lattice vibrations or phonons of a vdWH provide rich information,such as lattice structure,phonon dispersion,electronic band structure and electron–phonon coupling.Here,we provide a mini review on the lattice vibrations in vdWHs probed by Raman spectroscopy.First,we introduced different kinds of vdWHs,including their structures,properties and potential applications.Second,we discussed interlayer and intralayer phonon in twist multilayer graphene and MoS2.The frequencies of interlayer and intralayer modes can be reproduced by linear chain model(LCM)and phonon folding induced by periodical moiré potentials,respectively.Then,we extended LCM to vdWHs formed by distinct 2D materials,such as MoS2/graphene and hBN/WS2 heterostructures.We further demonstrated how to calculate Raman intensity of interlayer modes in vdWHs by interlayer polarizability model.