Dupont Maxime, Sherman Nicholas E, Moore Joel E
Department of Physics, University of California, Berkeley, California 94720, USA and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Phys Rev Lett. 2021 Sep 3;127(10):107201. doi: 10.1103/PhysRevLett.127.107201.
The stranglehold of low temperatures on fascinating quantum phenomena in one-dimensional quantum magnets has been challenged recently by the discovery of anomalous spin transport at high temperatures. Whereas both regimes have been investigated separately, no study has attempted to reconcile them. For instance, the paradigmatic quantum Heisenberg spin-1/2 chain falls at low temperature within the Tomonaga-Luttinger liquid framework, while its high-temperature dynamics is superdiffusive and relates to the Kardar-Parisi-Zhang universality class in 1+1 dimensions. This Letter aims at reconciling the two regimes. Building on large-scale matrix product state simulations, we find that they are connected by a temperature-dependent spatiotemporal crossover. As the temperature T is reduced, we show that the onset of superdiffusion takes place at longer length and timescales ∝1/T. This prediction has direct consequences for experiments including nuclear magnetic resonance: it is consistent with earlier measurements on the nearly ideal Heisenberg S=1/2 chain compound Sr_{2}CuO_{3}, yet calls for new and dedicated experiments.
最近，高温下反常自旋输运的发现对低温在一维量子磁体中迷人量子现象上的束缚提出了挑战。尽管这两种情况都已分别进行了研究，但尚未有研究尝试将它们统一起来。例如，典型的量子海森堡自旋-1/2链在低温下属于汤川-卢廷格液体框架，而其高温动力学是超扩散的，并且与1 + 1维的卡达尔-帕里西-张普适类相关。本论文旨在调和这两种情况。基于大规模矩阵乘积态模拟，我们发现它们通过一个依赖于温度的时空交叉区域相连。随着温度T降低，我们表明超扩散的起始发生在更长的长度和时间尺度上，比例为∝1/T。这一预测对包括核磁共振在内的实验有直接影响：它与早期对近乎理想的海森堡S = 1/2链化合物Sr₂CuO₃的测量结果一致，但需要新的专门实验。
