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
1 Editorial Prof.J.Michael Kosterlitz is the 2016 Nobel Prize Winner for Physics.Through his career,he overturned the conventional understanding that two-dimensional systems could not undergo phase transitions due to ...1 Editorial Prof.J.Michael Kosterlitz is the 2016 Nobel Prize Winner for Physics.Through his career,he overturned the conventional understanding that two-dimensional systems could not undergo phase transitions due to thermal fluctuations,along with David Thouless.They showed that vortex-antivortex pairs play a key role in phase transitions,leading to a topological phase transition now known as the Kosterlitz-Thouless(KT)transition.He is a true trailblazer in breaking the disciplines’boundary,his idea of implementing topology—a subfield of mathematics—in exploring physics has been transformative.He is an adventurer who cares most about the fun of exploring science.Scientists are paid to have fun,said by him.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
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.
文摘1 Editorial Prof.J.Michael Kosterlitz is the 2016 Nobel Prize Winner for Physics.Through his career,he overturned the conventional understanding that two-dimensional systems could not undergo phase transitions due to thermal fluctuations,along with David Thouless.They showed that vortex-antivortex pairs play a key role in phase transitions,leading to a topological phase transition now known as the Kosterlitz-Thouless(KT)transition.He is a true trailblazer in breaking the disciplines’boundary,his idea of implementing topology—a subfield of mathematics—in exploring physics has been transformative.He is an adventurer who cares most about the fun of exploring science.Scientists are paid to have fun,said by him.
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.
