arXiv subjects

Wu-Ming Liu

Publications and source records attributed to Wu-Ming Liu.

168 records · Page 10Linked to original sources

arXiv2010

Abelian and Non-Abelian Quantum Geometric Tensor

We propose a generalized quantum geometric tenor to understand topological quantum phase transitions, which can be defined on the parameter space with the adiabatic evolution of a quantum many-body system. The generalized quantum geometric tenor contains two different local measurements, the non-Abelian Riemannian metric and the non-Abelian Berry curvature, which are recognized as two natural geometric characterizations for the change of the ground-state properties when the parameter of the Hamiltonian varies. Our results show the symmetry-breaking and topological quantum phase transitions can be understood as the singular behavior of the local and topological properties of the quantum geometric tenor in the thermodynamic limit.

quant-ph↗

arXiv2010

Effects of Geometrical Symmetry on the Vortex Nucleation and Penetration in Mesoscopic Superconductors

We investigate how the geometrical symmetry affects the penetration and arrangement of vortices in mesoscopic superconductors using self-consistent Bogoliubov-de Gennes equations. We find that the entrance of the vortex happens when the current density at the hot spots reaches the depairing current density. Through determining the spatial distribution of hot spots, the geometrical symmetry of the superconducting sample influences the nucleation and entrance of vortices. Our results propose one possible experimental approach to control and manipulate the quantum states of mesoscopic superconductors with their topological geometries, and they can be easily generalized to the confined superfluids and Bose-Einstein condensates.

cond-mat.supr-con↗

arXiv2010

Interacting Dirac Fermions on Honeycomb Lattice

We investigate the interacting Dirac fermions on honeycomb lattice by cluster dynamical mean-field theory (CDMFT) combined with continuous time quantum Monte Carlo simulation (CTQMC). A novel scenario for the semimetal-Mott insulator transition of the interacting Dirac fermions is found beyond the previous DMFT studies. We demonstrate that the non-local spatial correlations play a vital role in the Mott transition on the honeycomb lattice. We also elaborate the experimental protocol to observe this phase transition by the ultracold atoms on optical honeycomb lattice.

cond-mat.str-el↗

arXiv2009

Spin squeezing in a generalized one-axis twisting model

We investigate the dependence of spin squeezing on the polar angle of the initial coherent spin state $|θ_0, ϕ_0>$ in a generalized one-axis twisting model, where the detuning $δ$ is taken into account. We show explicitly that regardless of $δ$ and $ϕ_0$, previous results of the ideal one-axis twisting is recovered as long as $θ_0=π/2$. For a small departure of $θ_0$ from $π/2$, however, the achievable variance $(V_{-})_{\min}\sim N^{2/3}$, larger than the ideal case $N^{1/3}$. We also find that the maximal-squeezing time $t_{\min}$ scales as $N^{-5/6}$. Analytic expressions of $(V_{-})_{\min}$ and $t_{\min}$ are presented, which agree with numerical simulations.

quant-ph↗

arXiv2007

Cavity-QED with cold atoms trapped in a double-well potential

We investigate the interplay dynamics of a cavity qed system, where the two-level atoms are trapped in a double-well potential, and the cavity mode, with a frequency largely detuned to the atomic level splitting, is driven by a probe laser. The interaction between the center-of-mass motion of the atoms and the cavity mode is induced by the position dependent atom-field coupling. The dynamics of the system is characterized by two distinct time scales, the inverse of the atomic interwell tunneling rate and the inverse of the cavity loss rate. The system shows drastically different (quasi) steady behaviors in the short-time and long-time intervals.

quant-ph↗

arXiv2004

Collapses and revivals of exciton emission in a semiconductor microcavity: detuning and phase-space filling effects

We investigate exciton emission of quantum well embedded in a semiconductor microcavity. The analytical expressions of the light intensity for the cases of excitonic number state and coherent state are presented by using secular approximation. Our results show that the effective exciton-exciton interaction leads to the appearance of collapse and revival of the light intensity. The revival time is twice compared the coherent state case with that of the number state. The dissipation of the exciton-polariton lowers the revival amplitude but does not alter the revival time. The influences of the detuning and the phase-space filling are studied. We find that the effect of the higher-order exciton-photon interaction may be removed by adjusting the detuning.

quant-ph↗