非线性 Thouless 泵浦是对传统 Thouless 泵浦理论的重要拓展,它揭示了非线性效应对拓扑系统中波包演化的影响。量子液滴作为超冷原子领域的新兴物态,因其在极稀薄环境中仍能稳定存在的独特性质,成为当前研究的焦点。因此,对量子液滴在...非线性 Thouless 泵浦是对传统 Thouless 泵浦理论的重要拓展,它揭示了非线性效应对拓扑系统中波包演化的影响。量子液滴作为超冷原子领域的新兴物态,因其在极稀薄环境中仍能稳定存在的独特性质,成为当前研究的焦点。因此,对量子液滴在超晶格中的非线性 Thouless 泵浦的研究具有极高的学术价值和应用前景。本文给出了量子液滴在不同相互作用强度下的非线性 Thouless 泵浦图。发现量子液滴中非线性项能够促使波包形成稳定的孤子结构,这些孤子在拓扑保护的作用下实现了空间上的拓扑输运,输运距离与系统的陈数紧密相关。随着非线性效应强度的增加,孤子不仅稳定存在,还发生了能带间的耦合,导致孤子在不同能带之间发生拉比振荡,影响了波包的传输行为。此外,本文通过改变相互作用系数,深入研究了量子液滴的陈数与相互作用强度之间的关系,得到了陈数随着相互作用系数的增大而增大,但是相互作用项对陈数的影响相对有限的结论。Nonlinear Thouless pumping represents a significant extension of the conventional Thouless pumping theory, revealing the influence of nonlinear effects on wave-packet evolution in topological systems. Quantum droplets, as an emerging quantum state in ultracold atomic systems, have become a focal point of current research due to their unique ability to remain stable in extremely dilute environments. Therefore, investigating the nonlinear Thouless pumping of quantum droplets in superlattices holds substantial academic value and application potential. This paper presents the nonlinear Thouless pumping diagrams of quantum droplets under varying interaction strengths. It is found that the nonlinear terms in quantum droplets facilitate the formation of stable solitonic structures, which achieve spatially quantized topological transport under topological protection, with the transport distance closely tied to the system’s Chern number. As the strength of nonlinearity increases, solitons not only remain stable but also exhibit interband coupling, leading to Rabi oscillations between distinct energy bands that modify the wave-packet dynamics. Furthermore, by tuning the interaction coefficients, this work systematically explores the relationship between the Chern number and interaction strength in quantum droplets. The results demon- strate that while the Chern number increases with interaction strength, the impact of nonlinear interactions on the Chern number remains relatively limited.展开更多
Coupled-waveguide devices are essential in photonic integrated circuits for coupling,polarization handling,and mode manipulation.However,the performance of these devices usually suffers from high wavelength and struct...Coupled-waveguide devices are essential in photonic integrated circuits for coupling,polarization handling,and mode manipulation.However,the performance of these devices usually suffers from high wavelength and structure sensitivity,which makes it challenging to realize broadband and reliable on-chip optical functions.Recently,topological pumping of edge states has emerged as a promising solution for implementing robust optical couplings.In this paper,we propose and experimentally demonstrate broadband on-chip mode manipulation with very large fabrication tolerance based on the Rice–Mele modeled silicon waveguide arrays.The Thouless pumping mechanism is employed in the design to implement broadband and robust mode conversion and multiplexing.The experimental results prove that various mode-order conversions with low insertion losses and intermodal crosstalk can be achieved over a broad bandwidth of 80 nm ranging from 1500 to 1580 nm.Thanks to such a topological design,the device has a remarkable fabrication tolerance of±70 nm for the structural deviations in waveguide width and gap distance,which is,to the best of our knowledge,the highest among the coupled-waveguide mode-handling devices reported so far.As a proof-of-concept experiment,we cascade the topological mode-order converters to form a four-channel mode-division multiplexer and demonstrate the transmission of a 200-Gb/s 16-quadrature amplitude modulation signal for each mode channel,with the bit error rates below the 7%forward error correction threshold of 3.8×10^(-3).We reveal the possibility of developing new classes of broadband and fabrication-tolerant coupled-waveguide devices with topological photonic approaches,which may find applications in many fields,including optical interconnects,quantum communications,and optical computing.展开更多
By means of the numerical renormalization group method, we study the phase transition, the spectral property, and the temperature-dependent magnetic moment for a parallel double dot system with level difference, where...By means of the numerical renormalization group method, we study the phase transition, the spectral property, and the temperature-dependent magnetic moment for a parallel double dot system with level difference, where the dot energies are kept symmetric to the half-filled level. A Kosterlitz–Thouless（KT） transition between local spin triplet and singlet is found. In the triplet regime, the local spin is partially screened by the conduction leads and spin-1 Kondo effect is realized.While for the singlet, the Kondo peak is strongly suppressed and the magnetic moment decreases to 0 at a definite low temperature. We attribute this KT transition to the breaking of the reflection symmetry, resulting from the difference of the charge occupations of the two dots. To understand this KT transition and related critical phenomena, detailed scenarios are given in the transmission coefficient and the magnetic moment, and an effective Kondo model refers to the RayleighSchrdinger perturbation theory is used.展开更多
The transport property and phase transition for a parallel triple dot device are studied by adopting Wilson＇s numerical renormalization group technique, focusing on the effects of level spacings between neighboring d...The transport property and phase transition for a parallel triple dot device are studied by adopting Wilson＇s numerical renormalization group technique, focusing on the effects of level spacings between neighboring dot sites. By keeping dot 2at the half-filled level and tuning the level differences, it is demonstrated that the system transits from local spin quadruplet to triplet and doublet sequently, and three kinds of Kondo peaks at the Fermi surface could be found, which are separated by two Kosterlitz–Thouless type quantum phase transitions and correspond to spin-3/2, spin-1, and spin-1/2 Kondo effect,respectively. To obtain a detailed understanding of these problems, the charge occupation, the spin–spin correlation, the transmission coefficient, and the temperature-dependent magnetic moment are shown, and necessary physical arguments are given.展开更多
The Rice–Mele model has been a seminal prototypical model for the study of topological phenomena such as Thouless pumping.Here we implement the interacting Rice–Mele model using a superconducting quantum processor c...The Rice–Mele model has been a seminal prototypical model for the study of topological phenomena such as Thouless pumping.Here we implement the interacting Rice–Mele model using a superconducting quantum processor comprising a one-dimensional array of 36 qutrits.By adiabatically cycling the qutrit frequencies and hopping strengths in the parametric space,we emulate the Thouless pumping of single and two bounded microwave photons along the qutrit chain.Furthermore,with strong Hubbard interaction inherent in the qutrits we also emulate the intriguing phenomena of resonant tunneling and asymmetric edge-state transport of two interacting photons.Utilizing the interactions and higher energy levels in such fully controlled synthetic quantum simulators,these results demonstrate new opportunities for exploring exotic topological phases and quantum transport phenomena using superconducting quantum circuits.展开更多
We consider the superconducting properties of Lieb lattice, which produces a flat-band energy spectrum in the normal state under the strong electron–electron correlation. Firstly, we show the hole-doping dependent su...We consider the superconducting properties of Lieb lattice, which produces a flat-band energy spectrum in the normal state under the strong electron–electron correlation. Firstly, we show the hole-doping dependent superconducting order amplitude with various electron–electron interaction strengths in the zero-temperature limit. Secondly, we obtain the superfluid weight and Berezinskii–Kosterlitz–Thouless(BKT) transition temperature with a lightly doping level. The large ratio between the gap-opening temperature and BKT transition temperature shows similar behavior to the pseudogap state in high-T_(c) superconductors. The BKT transition temperature versus doping level exhibits a dome-like shape in resemblance to the superconducting dome observed in the high-T_(c) superconductors. However, unlike the exponential dependence of T_(c) on the electron–electron interaction strength in the conventional high-T_(c) superconductors, the BKT transition temperature for a flat band system depends linearly on the electron–electron interaction strength. We also show the doping-dependent superconductivity on a lattice with the staggered hoping parameter in the end. Our predictions are amenable to verification in the ultracold atoms experiment and promote the understanding of the anomalous behavior of the superfluid weight in the high-T_(c) superconductors.展开更多
With the help of an improvement Monte Carlo method, the Berezinskii-Kosterlitz-Thouless phase transition arising in two-dimensional planar rotator model with weak Dzyaloshinsky-Moriya （DM） interaction is investigate...With the help of an improvement Monte Carlo method, the Berezinskii-Kosterlitz-Thouless phase transition arising in two-dimensional planar rotator model with weak Dzyaloshinsky-Moriya （DM） interaction is investigated. The effects of the DM interaction on specific heat, susceptibility, and magnetization are simulated. The critical temperature of transitions is determined by the so-called Binder cumulant and the susceptibility of finite-size scaling. We find that the chiral Z2 symmetry reduced by the DM interactions plays an important role in a two-dimensional XY spin system, typically, the critical temperature is sensitive to weak DM spin couplings.展开更多
The topological pumping has been instrumental in advancing our understanding of topological phase transitions in various physical systems,which can be extended to uncover intriguing higher-order topological phases in ...The topological pumping has been instrumental in advancing our understanding of topological phase transitions in various physical systems,which can be extended to uncover intriguing higher-order topological phases in the lower-dimensional system.Here,we propose a theoretical exploration of topological dipole pumping on an acoustic square superlattice by cyclically modulating intracell couplings,which shares the topological nature of an extended three-dimensional system with chiral hinge states.Using the multipole chiral numbers,we characterize the higher-order topological phases that arise during the evolution.The evolution of topological phase transitions is verified by numerical simulations and shows corner states are transferred across the bulk.Our findings can inspire the construction of chiral hinge states in artificial crystals,opening up new possibilities for the design of devices allowing the unidirectional propagation of sound.展开更多
文摘非线性 Thouless 泵浦是对传统 Thouless 泵浦理论的重要拓展,它揭示了非线性效应对拓扑系统中波包演化的影响。量子液滴作为超冷原子领域的新兴物态,因其在极稀薄环境中仍能稳定存在的独特性质,成为当前研究的焦点。因此,对量子液滴在超晶格中的非线性 Thouless 泵浦的研究具有极高的学术价值和应用前景。本文给出了量子液滴在不同相互作用强度下的非线性 Thouless 泵浦图。发现量子液滴中非线性项能够促使波包形成稳定的孤子结构,这些孤子在拓扑保护的作用下实现了空间上的拓扑输运,输运距离与系统的陈数紧密相关。随着非线性效应强度的增加,孤子不仅稳定存在,还发生了能带间的耦合,导致孤子在不同能带之间发生拉比振荡,影响了波包的传输行为。此外,本文通过改变相互作用系数,深入研究了量子液滴的陈数与相互作用强度之间的关系,得到了陈数随着相互作用系数的增大而增大,但是相互作用项对陈数的影响相对有限的结论。Nonlinear Thouless pumping represents a significant extension of the conventional Thouless pumping theory, revealing the influence of nonlinear effects on wave-packet evolution in topological systems. Quantum droplets, as an emerging quantum state in ultracold atomic systems, have become a focal point of current research due to their unique ability to remain stable in extremely dilute environments. Therefore, investigating the nonlinear Thouless pumping of quantum droplets in superlattices holds substantial academic value and application potential. This paper presents the nonlinear Thouless pumping diagrams of quantum droplets under varying interaction strengths. It is found that the nonlinear terms in quantum droplets facilitate the formation of stable solitonic structures, which achieve spatially quantized topological transport under topological protection, with the transport distance closely tied to the system’s Chern number. As the strength of nonlinearity increases, solitons not only remain stable but also exhibit interband coupling, leading to Rabi oscillations between distinct energy bands that modify the wave-packet dynamics. Furthermore, by tuning the interaction coefficients, this work systematically explores the relationship between the Chern number and interaction strength in quantum droplets. The results demon- strate that while the Chern number increases with interaction strength, the impact of nonlinear interactions on the Chern number remains relatively limited.
基金supported by the National Key R&D Program of China(Grant No.2023YFB2905503)the National Natural Science Foundation of China(Grant Nos.62035016,62105200,62475146,and 62341508).
文摘Coupled-waveguide devices are essential in photonic integrated circuits for coupling,polarization handling,and mode manipulation.However,the performance of these devices usually suffers from high wavelength and structure sensitivity,which makes it challenging to realize broadband and reliable on-chip optical functions.Recently,topological pumping of edge states has emerged as a promising solution for implementing robust optical couplings.In this paper,we propose and experimentally demonstrate broadband on-chip mode manipulation with very large fabrication tolerance based on the Rice–Mele modeled silicon waveguide arrays.The Thouless pumping mechanism is employed in the design to implement broadband and robust mode conversion and multiplexing.The experimental results prove that various mode-order conversions with low insertion losses and intermodal crosstalk can be achieved over a broad bandwidth of 80 nm ranging from 1500 to 1580 nm.Thanks to such a topological design,the device has a remarkable fabrication tolerance of±70 nm for the structural deviations in waveguide width and gap distance,which is,to the best of our knowledge,the highest among the coupled-waveguide mode-handling devices reported so far.As a proof-of-concept experiment,we cascade the topological mode-order converters to form a four-channel mode-division multiplexer and demonstrate the transmission of a 200-Gb/s 16-quadrature amplitude modulation signal for each mode channel,with the bit error rates below the 7%forward error correction threshold of 3.8×10^(-3).We reveal the possibility of developing new classes of broadband and fabrication-tolerant coupled-waveguide devices with topological photonic approaches,which may find applications in many fields,including optical interconnects,quantum communications,and optical computing.
基金supported by the National Natural Science Foundation of China(Grant No.11504102)the Special Fund for Theoretical Physics of the National Natural Science Foundation of China(Grant No.11647133)+1 种基金the Doctoral Scientific Research Foundation of China(Grant No.BK201407)the Major Scientific Research Project Pre-funds of Hubei University of Automotive Technology,China(Grant No.2014XY06)
文摘By means of the numerical renormalization group method, we study the phase transition, the spectral property, and the temperature-dependent magnetic moment for a parallel double dot system with level difference, where the dot energies are kept symmetric to the half-filled level. A Kosterlitz–Thouless（KT） transition between local spin triplet and singlet is found. In the triplet regime, the local spin is partially screened by the conduction leads and spin-1 Kondo effect is realized.While for the singlet, the Kondo peak is strongly suppressed and the magnetic moment decreases to 0 at a definite low temperature. We attribute this KT transition to the breaking of the reflection symmetry, resulting from the difference of the charge occupations of the two dots. To understand this KT transition and related critical phenomena, detailed scenarios are given in the transmission coefficient and the magnetic moment, and an effective Kondo model refers to the RayleighSchrdinger perturbation theory is used.
基金Project supported by the National Natural Science Foundation of China(Grant No.11504102)the Scientific Research Items Foundation of Hubei Educational Committee,China(Grant Nos.Q20161803 and B2016091)+1 种基金the Doctoral Scientific Research Foundation(Grant No.BK201407)the Major Scientific Research Project Pre-funds of Hubei University of Automotive Technology,China(Grant No.2014XY06)
文摘The transport property and phase transition for a parallel triple dot device are studied by adopting Wilson＇s numerical renormalization group technique, focusing on the effects of level spacings between neighboring dot sites. By keeping dot 2at the half-filled level and tuning the level differences, it is demonstrated that the system transits from local spin quadruplet to triplet and doublet sequently, and three kinds of Kondo peaks at the Fermi surface could be found, which are separated by two Kosterlitz–Thouless type quantum phase transitions and correspond to spin-3/2, spin-1, and spin-1/2 Kondo effect,respectively. To obtain a detailed understanding of these problems, the charge occupation, the spin–spin correlation, the transmission coefficient, and the temperature-dependent magnetic moment are shown, and necessary physical arguments are given.
基金supported by the National Natural Science Foundation of China(Nos.12174178,11905098,12204228,12374474,12025509,and 12275365)the Key-Area Research and Development Program of Guangdong Province(No.2018B030326001)+4 种基金the Guangdong Provincial Key Laboratory(No.2019B121203002)the Science,Technology and Innovation Commission of Shenzhen Municipality(Nos.KYTDPT20181011104202253,KQTD20210811090049034,and K21547502)the Innovation Program for Quantum Science and Technology(No.2021ZD0301703)the Shenzhen-Hong Kong Cooperation Zone for Technology and Innovation(No.HZQB-KCZYB-2020050)the NSF of Beijing(No.Z190012),and the National Key Research and Development Program of China(Nos.2022YFA1404104 and 2024A1515011714).
文摘The Rice–Mele model has been a seminal prototypical model for the study of topological phenomena such as Thouless pumping.Here we implement the interacting Rice–Mele model using a superconducting quantum processor comprising a one-dimensional array of 36 qutrits.By adiabatically cycling the qutrit frequencies and hopping strengths in the parametric space,we emulate the Thouless pumping of single and two bounded microwave photons along the qutrit chain.Furthermore,with strong Hubbard interaction inherent in the qutrits we also emulate the intriguing phenomena of resonant tunneling and asymmetric edge-state transport of two interacting photons.Utilizing the interactions and higher energy levels in such fully controlled synthetic quantum simulators,these results demonstrate new opportunities for exploring exotic topological phases and quantum transport phenomena using superconducting quantum circuits.
基金supported by the National Natural Science Foundation of China(Grant No.11804213)the Scientific Research Program Funded by Shaanxi Provincial Education Department(Grant No.20JK0573)+1 种基金the Scientific Research Foundation of Shaanxi University of Technology(Grant No.SLGRCQD2006)the Natural Science Basic Research Program of Shaanxi(Grant No.2021JQ-748)。
文摘We consider the superconducting properties of Lieb lattice, which produces a flat-band energy spectrum in the normal state under the strong electron–electron correlation. Firstly, we show the hole-doping dependent superconducting order amplitude with various electron–electron interaction strengths in the zero-temperature limit. Secondly, we obtain the superfluid weight and Berezinskii–Kosterlitz–Thouless(BKT) transition temperature with a lightly doping level. The large ratio between the gap-opening temperature and BKT transition temperature shows similar behavior to the pseudogap state in high-T_(c) superconductors. The BKT transition temperature versus doping level exhibits a dome-like shape in resemblance to the superconducting dome observed in the high-T_(c) superconductors. However, unlike the exponential dependence of T_(c) on the electron–electron interaction strength in the conventional high-T_(c) superconductors, the BKT transition temperature for a flat band system depends linearly on the electron–electron interaction strength. We also show the doping-dependent superconductivity on a lattice with the staggered hoping parameter in the end. Our predictions are amenable to verification in the ultracold atoms experiment and promote the understanding of the anomalous behavior of the superfluid weight in the high-T_(c) superconductors.
基金The project supported by Natural Science Foundation of Hubei Province of China under Grant No. 2003ABA004. We are indebted to professor Wang Jian-Sheng for his stimulating discussions.
文摘With the help of an improvement Monte Carlo method, the Berezinskii-Kosterlitz-Thouless phase transition arising in two-dimensional planar rotator model with weak Dzyaloshinsky-Moriya （DM） interaction is investigated. The effects of the DM interaction on specific heat, susceptibility, and magnetization are simulated. The critical temperature of transitions is determined by the so-called Binder cumulant and the susceptibility of finite-size scaling. We find that the chiral Z2 symmetry reduced by the DM interactions plays an important role in a two-dimensional XY spin system, typically, the critical temperature is sensitive to weak DM spin couplings.
基金supported by the National Key R&D Program of China(Grant No.2022YFA1404402)the National Natural Science Foundation of China(Grant Nos.11634006,and 81127901)+1 种基金the High-Performance Computing Center of Collaborative Innovation Center of Advanced Microstructuresa Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions。
文摘The topological pumping has been instrumental in advancing our understanding of topological phase transitions in various physical systems,which can be extended to uncover intriguing higher-order topological phases in the lower-dimensional system.Here,we propose a theoretical exploration of topological dipole pumping on an acoustic square superlattice by cyclically modulating intracell couplings,which shares the topological nature of an extended three-dimensional system with chiral hinge states.Using the multipole chiral numbers,we characterize the higher-order topological phases that arise during the evolution.The evolution of topological phase transitions is verified by numerical simulations and shows corner states are transferred across the bulk.Our findings can inspire the construction of chiral hinge states in artificial crystals,opening up new possibilities for the design of devices allowing the unidirectional propagation of sound.
