Souslov Anton, Dasbiswas Kinjal, Fruchart Michel, Vaikuntanathan Suriyanarayanan, Vitelli Vincenzo
The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
Department of Physics, University of Bath, Bath BA2 7AY, United Kingdom.
Phys Rev Lett. 2019 Mar 29;122(12):128001. doi: 10.1103/PhysRevLett.122.128001.
Fluids in which both time reversal and parity are broken can display a dissipationless viscosity that is odd under each of these symmetries. Here, we show how this odd viscosity has a dramatic effect on topological sound waves in fluids, including the number and spatial profile of topological edge modes. Odd viscosity provides a short-distance cutoff that allows us to define a bulk topological invariant on a compact momentum space. As the sign of odd viscosity changes, a topological phase transition occurs without closing the bulk gap. Instead, at the transition point, the topological invariant becomes ill defined because momentum space cannot be compactified. This mechanism is unique to continuum models and can describe fluids ranging from electronic to chiral active systems.
时间反演和平移对称性均被破坏的流体能够展现出一种无耗散粘性，这种粘性在上述每种对称性下都是反对称的。在此，我们展示了这种反对称粘性如何对流体中的拓扑声波产生显著影响，包括拓扑边缘模的数量和空间分布。反对称粘性提供了一个短距离截止，使我们能够在紧致动量空间上定义一个体拓扑不变量。随着反对称粘性符号的改变，会发生拓扑相变，且体能隙不会闭合。相反，在相变点，拓扑不变量变得定义不明确，因为动量空间无法被紧致化。这种机制是连续统模型所特有的，并且可以描述从电子系统到手性活性系统等各种流体。
