标题： 手性原子超流在双谷光晶格中的残余序熔化 显示英文标题

标题： Vestigial Order Melting of a Chiral Atomic Superfluid in a Double-Valley Optical Lattice

摘要： 量子模拟在多轨道超流体中的残余序在冷原子和凝聚态系统中一直吸引着持续的研究兴趣，因为它为高温超导性提供了有价值的见解。 在这里，我们实验研究了通过抖动光晶格中超冷玻色原子实现的Floquet工程双谷能带结构中的热相变。 该系统同时表现出 U(1) 和时间反演 $\mathbb{Z}_2$ 对称性，在基态下，它形成一个具有单个谷的贝塞-爱因斯坦凝聚的手征超流体。通过调节温度，我们观察到手征超流体的残余序熔化：首先变为顺磁超流体，然后变为正常相。 我们在一系列驱动频率范围内测量了超流和伊辛转变温度，并发现超流转变的临界温度始终高于所研究频率范围内的伊辛转变温度。 当频率接近共振时，伊辛转变温度降低，而超流转变温度几乎不受影响。 在远失谐的情况下，两个相变合并为一个相变。 我们的实验结果表明，在周期性驱动的量子系统中，量子和热涨落的相互作用蕴含丰富的量子多体物理。 显示英文摘要

摘要： Quantum simulations of vestigial orders in multi-orbital superfluids have been attracting continuous research interests in both cold atoms and condensed matter systems, as it provides valuable insights into the high-temperature superconductivity. Here, we experimentally investigate thermal phase transitions in a Floquet-engineered double-valley bandstructure realized with ultracold bosonic atoms in a shaken optical lattice. The system exhibits both U(1) and time-reversal $\mathbb{Z}_2$ symmetries, and in the ground state, it forms a chiral superfluid with the Bose-Einstein condensation at a single valley.By tuning the temperature, we observe a vestigial order melting of the chiral superfluid: first into a paramagnetic superfluid, and then into a normal phase. We measure the superfluid and Ising transition temperatures across a range of driving frequencies, and find that the critical temperature of the superfluid transition is always higher than that of Ising transition within the studied frequency range. As the frequency approaches the resonance, the Ising transition temperature decreases, while the superfluid transition temperature remains almost unaffected. The two phase transitions merge into a single transition at far detuning. Our experimental results imply rich quantum many-body physics as an interplay of quantum and thermal fluctuations in periodically driven quantum systems.