arXiv subjects

Chuan-Yin Xia

Publications and source records attributed to Chuan-Yin Xia.

25 records · Page 2Linked to original sources

arXiv2021

Topological defects as relics of spontaneous symmetry breaking from black hole physics

Formation and evolution of topological defects in course of non-equilibrium symmetry breaking phase transitions is of wide interest in many areas of physics, from cosmology through condensed matter to low temperature physics. Its study in strongly coupled systems, in absence of quasiparticles, is especially challenging. We investigate breaking of U(1) symmetry and the resulting spontaneous formation of vortices in a $(2+1)$-dimensional holographic superconductor employing gauge/gravity duality, a `first-principles' approach to study strongly coupled systems. Magnetic fluxons with quantized fluxes are seen emerging in the post-transition superconducting phase. As expected in type II superconductors, they are trapped in the cores of the order parameter vortices. The dependence of the density of these topological defects on the quench time, the dispersion of the typical winding numbers in the superconductor, and the vortex-vortex correlations are consistent with predictions of the Kibble-Zurek mechanism.

hep-th↗

arXiv2021

Uniform quenching processes in a holographic s+p model with reentrance

We study the homogenous quenching processes in a holographic s+p model with reentrant phase transitions. We first realize the reentrant phase transition in the holographic model in probe limit and draw the phase diagram. Next, we compare the time evolution of the two condensates in two groups of numerical quenching experiments across the reentrant region, with different quenching speed as well as different width of the reentrant region, respectively. We also study the dynamical competition between the two orders in quenching processes from the normal phase to the superconductor phase.

hep-th↗

arXiv2020

Winding up a finite size holographic superconducting ring beyond Kibble-Zurek mechanism

We studied the dynamics of the order parameter and the winding numbers $W$ formation of a quenched normal-to-superconductor state phase transition in a finite size holographic superconducting ring. There is a critical circumference $\tilde{C}$ below it no winding number will be formed, then $\tilde{C}$ can be treated as the Kibble-Zurek mechanism (KZM) correlation length $ξ$ which is proportional to the fourth root of its quench rate $τ_Q$, which is also the average size of independent pieces formed after a quench. When the circumference $C \geq 10 ξ$, the key KZM scaling between the average value of absolute winding number and the quench rate $\langle|W|\rangle \propto τ_Q^{-1/8}$ is observed. At smaller sizes, the universal scaling will be modified, there are two regions. The middle size $5ξ<C<10ξ$ result $\langle|W|\rangle \propto τ_Q^{-1/5}$ agrees with a finite size experiment observation. While at $ξ<C\leq 5ξ$ the the average value of absolute winding number equals to the variance of winding number and there is no well exponential relationship between the quench rate and the average value of absolute winding number. The winding number statistics can be derived from a trinomial distribution with $\tilde{N}=C/ (f ξ)$ trials, $f\simeq 5$ is the average number of adjacent pieces that are effectively correlated.

hep-th↗

arXiv2020

Formation and critical dynamics of topological defects in Lifshitz holography

We examine the formation and critical dynamics of topological defects via Kibble-Zurek mechanism in a (2+1)-dimensional quantum critical point, which is conjectured to dual to a Lifshitz geometry. Quantized magnetic fluxoids are spontaneously generated and trapped in the cores of order parameter vortices, which is a feature of type II superconductors. Time evolution of the average condensate is found to lag behind the instantaneous equilibrium value of the order parameter, a typical phenomenon in nonequilibrium dynamics. Scalings of vortex number density and the "freeze-out" time match the predictions from Kibble-Zurek mechanism. From these scalings, the dynamic and static critical exponents in the boundary field theory are found, at least at finite temperature, to be irrespective of the Lifshitz exponent in the bulk.

hep-th↗

arXiv2020

Fractional and Integer Vortex Dynamics in Strongly Coupled Two-component Bose-Einstein Condensates from AdS/CFT Correspondence

In order to study the rotating strongly coupled Bose-Einstein condensations(BEC), a holographic model defined in an AdS black hole that duals to a coupled two-component condensations in global $U(1)$ symmetry broken phase with intercomponent coupling $η$ and internal coherent coupling $ε$ is proposed. By solving the dynamics of the model, we study the process of formation and also the crossover from fractional to integer vortex phases. With changing only $η$ from zero to a finite value, fractional vortex lattices undergo a transition from hexagon to square lattice and finally to vortex sheets. By continuing to turn on $ε$, we find that two fractional vortices in different components constitute dimers, and when $η$ transcend a critical value, multi-dimer like hexamer or tetramer made up of two and three dimers appear. As $ε$ keeps increasing, some dimers rotate to adjust themselves and then constitute the lattice of integer vortices. Under an initial conditions similar to an spinor BEC vortices dynamics experiment, the appearance of disordered turbulence is found in the process of fractional vortex generation, which matches the experimental observation. While in the formation process of integer vortices, the appearance of grooves is predicted.

cond-mat.quant-gas↗

arXiv2019

Phase Separation and Exotic Vortex Phases in a Two-Species Holographic Superfluid

At a finite temperature, the stable equilibrium states of a coupled two-component superfluid with the same mass in both non-rotating and rotating cases can be obtained by studying its real time dynamics via holography, the equilibrium state is the final stable state that does not change in time anymore in the evolution process . Without rotation, the spatial phase separated states of the two components become more stable than the miscible condensates state when the direct repulsive inter-component coupling constant $η>η_c=0.05$ when the Josephson coupling $ε$ is turned off. While a finite $ε$ will always prevent the two species to be separated spatially. Under rotation, with vanishing $ε$, the quantum fluid reveals many equilibrium structures of vortex states by varying the $η$ from negative to positive, the interlaced vortex lattices undergo a phase transition to vortex sheets with each component made up of chains of single quantized vortices.

hep-th↗

arXiv2019

Vortex Lattice in a Rotating Holographic Superfluid

By utilizing the AdS/CFT correspondence, we explore the dynamics of strongly coupled superfluid vortices in a disk with constant angular velocity. Each vortex in the vortex lattice is quantized with vorticity one from the direct inspection of their phases. As the angular velocity of the disk is greater than a critical value, the first vortex will be excited as expected from theoretical predictions. The subsequent two and more vortices are also generated by increasingly rotating the disk, resulting in the remarkable step transitions for the angular velocity to excite each individual vortex. When the vortex number is large enough, the density of vortices is found to be linearly proportional to the angular velocity, which matches the Feynman relation very well.

hep-th↗