两条腿通量阶梯上相互作用玻色子的温度特性
Finite-temperature properties of interacting bosons on a two-leg flux ladder
摘要：
具有人工规范场的磁通梯等准一维晶格系统拥有丰富的量子相图，引起了人们极大的兴趣。然而，到目前为止，这些系统的大部分工作都集中在零温度阶段，而相应的有限温度制度仍然在很大程度上未被探索。零温度相的温度特性特征是否持续以及持续到哪一个温度特性特征的问题在实验实现中是相关的。我们研究了均匀磁场中的两足梯形晶格，并集中研究了手征边缘电流和动量分布函数，这是超冷量子气体实验中的关键观测量。这些数量计算的硬核玻色子以及非相互作用玻色子和无自旋费米子在零和有限的温度。我们采用了一种基于矩阵乘积态的纯化方法来模拟有限温度下的强相互作用玻色子，并分析了有限尺寸效应。我们的主要结果涉及强相互作用玻色子的涡旋流体迈斯纳交叉。我们证明，在高温下，仍然可以从动量分布函数中的特征有限动量最大值中检测到涡旋流体相的特征，而涡旋流体相在局部梯级电流和手征边缘电流中留下较弱的指纹。为了确定可以观察到这些签名的温度范围，我们引入了一个合适的措施，这些最大值的对比度。结果被压缩成一个有限温度的交叉图的硬核玻色子。
英文摘要：
Quasi-one-dimensional lattice systems such as flux ladders with artificial gauge fields host rich quantum-phase diagrams that have attracted great interest. However, so far, most of the work on these systems has concentrated on zero-temperature phases while the corresponding finite-temperature regime remains largely unexplored. The question if and up to which temperature characteristic features of the zero-temperature phases persist is relevant in experimental realizations. We investigate a two-leg ladder lattice in a uniform magnetic field and concentrate our study on chiral edge currents and momentum-distribution functions, which are key observables in ultracold quantum-gas experiments. These quantities are computed for hard-core bosons as well as noninteracting bosons and spinless fermions at zero and finite temperatures. We employ a matrix-product-state based purification approach for the simulation of strongly interacting bosons at finite temperatures and analyze finite-size effects. Our main results concern the vortex-fluid-to-Meissner crossover of strongly interacting bosons. We demonstrate that signatures of the vortex-fluid phase can still be detected at elevated temperatures from characteristic finite-momentum maxima in the momentum-distribution functions, while the vortex-fluid phase leaves weaker fingerprints in the local rung currents and the chiral edge current. In order to determine the range of temperatures over which these signatures can be observed, we introduce a suitable measure for the contrast of these maxima. The results are condensed into a finite-temperature crossover diagram for hard-core bosons.
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