Universal spatiotemporal dynamics of spontaneous superfluidity breakdown in the presence of synthetic gauge fields

Abstract

According to the famous Kibble-Zurek mechanism (KZM), the universality of spontaneous defect generation in continuous phase transitions (CPTs) can be understood by the critical slowing down. In most CPTs of atomic Bose-Einstein condensates (BECs), the universality of spontaneous defect generations has been explained by the divergent relaxation time associated with the nontrivial gapless Bogoliubov excitations. However, for atomic BECs in synthetic gauge fields, their spontaneous superfluidity breakdown is resulted from the divergent correlation length associated with the zero Landau critical velocity. Here, by considering an atomic BEC ladder subjected to a synthetic magnetic field, we reveal that the spontaneous superfluidity breakdown obeys the KZM. The Kibble-Zurek scalings are derived from the Landau critical velocity which determines the correlation length. In further, the critical exponents are numerically extracted from the critical spatial-temporal dynamics of the bifurcation delay and the spontaneous vortex generation. Our study provides a general way to explore and understand the spontaneous superfluidity breakdown in CPTs from a single-well dispersion to a double-well one, such as, BECs in synthetic gauge fields, spin-orbit coupled BECs, and BECs in shaken optical lattices.Introduction. Engineered synthetic gauge fields for neutral atoms [1-8] provide new opportunities to explore exotic collective quantum phenomena [9][10][11][12][13][14]. The dispersion relation plays an important role in the emergence of many collective quantum phenomena. Through controlling the applied external fields, the dispersion relation can be tuned from a single-well shape into a double-well one, such as, spin-orbit coupled quantum gases [15][16][17][18], ultracold atoms in shaken optical lattices [19][20][21] and Bose ladders within magnetic fields [22][23][24][25]. At the transition point, due to the interplay between the synthetic gauge fields and the atom-atom interactions, the Landau critical velocity vanishes [17,18,20] and thus the superfluid spontaneously breaks down. Such a spontaneous superfluidity breakdown is very different from the conventional Landau instability which requires the superfluid velocity exceeding a nonzero critical velocity [26][27][28]. Although the static phase transitions in synthetic gauge fields have been extensively studied, the underlying dynamics of phase transitions is still unclear.

Universal dynamics of superradiant phase transition in the anisotropic quantum Rabi model

“…Due to the gapless excitations at the critical point, the adiabaticity breaks down when a system goes through a continuous phase transition. As a consequence, nontrivial excitations such as domains [4][5][6][7][8][9][10][11][12][13][14], vortices [15][16][17] and solitons [18][19][20] appear spontaneously and obey the wellkonwn Kibble-Zurek mechanism (KZM) [3,4,[21][22][23][24][25]. The KZM has been extensively studied in various systems, from the early universe [3,4], condensed matter systems [26][27][28], trapped ions [29][30][31][32][33], to ultracold atomic gases [5-15, 18-20, 34-37].…”

Universality of miscible–immiscible phase separation dynamics in two-component Bose–Einstein condensates

“…The non-equilibrium dynamics of quantum phase transitions have attracted great interest in many branches of physics, including cosmology, particle physics and condensed matter physics [1][2][3]. When a system is driven across a phase transition and enters a symmetry broken phase, one of the most nontrivial results is the creation of topological defects, such as domains [4][5][6][7][8][9][10][11][12][13], vortices [14][15][16] and solitons [17][18][19]. The possibility to engineer a quantum phase transition and recover its universality from topological defects is of great significance in non-equilibrium physics [20].…”

Universal non-equilibrium dynamics in Bose condensed atomic gases undergoing spontaneous symmetry breaking

“…The ground-state property and its quench dynamics in two-component coupling atomic BEC trapped in deep 1D optical lattices [30 ] . 利用Bogoliubov理论，我们发现体系同时存在Goldstone模和Higgs模两种激发 [32 ] ，如图 [33 ] 、震动光学晶格中的超冷原子 [18] 和磁场中的玻色梯子链 [34 ] 等。 考虑人工规范场下的两条玻色梯子链 [35] ，如图 5(a)所示。该模型可由两路双色光形成 驻波场实现，体系的均匀规范势可由激光诱导产生。平均场下，其哈密顿量为 ( ) [37] ，长波极限下朗道临界速度 ( )…”

“…Figure 5 The ground-state property and its quench dynamics of a bosonic ladder in synthetic gauge fields [35] . 22 12 [39,40] 。 图6 淬火动力学及其临界标度 [39] 。(a,b,c) 在不同淬火时间下，局域自旋极化随时间的演化 过程；(d) 分离相基态；(e) 平均相变延迟和淬火时间的标度关系，插图为不同淬火时间下 序参量随时间演化图；(f) 平均畴数和淬火时间的标度关系。 Figure 6 Quenching dynamics and its critical scalings [39 ] .…”

“…Figure5The ground-state property and its quench dynamics of a bosonic ladder in synthetic gauge fields[35] . (a) The schematic diagram.…”