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Changjian Yu

Publications and source records attributed to Changjian Yu.

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Polarization-controlled pattern formation in antiparallel dipolar binary condensates

We investigate non-equilibrium pattern formation in an antiparallel two-component dipolar Bose-Einstein condensate by varying the polarization angle and the trap aspect ratio. At finite tilt, the condensate supports stripe order. Quenching the angle to zero triggers a roton-assisted, mushroom-like corrugation that destroys translational order and drives the system into labyrinthine textures, whereas a slow linear ramp produces long-lived curved stripes that ultimately converge to labyrinths. Population imbalance strongly biases the evolution: the minority component preferentially fragments into a stable droplet array while the majority remains comparatively diffuse; once formed, the droplet crystal is robust under polarization hysteresis with largely reversible shape changes and unchanged lattice topology. The trap aspect ratio controls both the initial stripe number and the instability timescale, with tighter axial confinement accelerating corrugation and yielding denser labyrinths at late times. All behaviors arise within a quasi-two-dimensional mean-field regime where beyond-mean-field corrections are negligible; accordingly, the droplets reported here are not self-bound in free space. The observed textures (such as stripes, curved stripes, and labyrinths) mirror the taxonomy and instability pathways of nuclear "pasta" morphologies (rods and slabs) known from neutron-star and supernova matter, highlighting polarization angle, trap geometry, and population imbalance as practical, experimentally accessible controls for selecting and steering patterns in dipolar mixtures.

cond-mat.quant-gas

Thermal effects on density-modulated phases in a dipolar Bose--Einstein condensate

Density-modulated phases in dipolar Bose--Einstein condensates arise from the competition between contact repulsion, long-range dipole--dipole interactions, and beyond-mean-field fluctuations. We examine finite-temperature stationary states of a harmonically trapped dipolar Bose gas using a temperature-dependent extended Gross--Pitaevskii equation within the local-density approximation. In this framework, the thermal correction shifts some structural boundaries toward larger scattering lengths and changes the parameter region in which connected density-modulated states are obtained. The density contrast changes sharply at $T = 0$, whereas at finite temperature it varies more gradually, consistent with a smooth crossover-like evolution in the finite trapped system. We also use Leggett's bound to estimate a geometric upper limit on the possible superfluid response for representative density profiles. These results suggest that finite-temperature corrections can reshape pattern formation in dipolar quantum gases.

cond-mat.quant-gas