Liang Sihang, Kushwaha Satya, Gao Tong, Hirschberger Max, Li Jian, Wang Zhijun, Stolze Karoline, Skinner Brian, Bernevig B A, Cava R J, Ong N P
Department of Physics, Princeton University, Princeton, NJ, USA.
Department of Chemistry, Princeton University, Princeton, NJ, USA.
Nat Mater. 2019 May;18(5):443-447. doi: 10.1038/s41563-019-0303-x. Epub 2019 Mar 4.
A recurring theme in topological matter is the protection of unusual electronic states by symmetry, for example, protection of the surface states in Z topological insulators by time-reversal symmetry. Recently, interest has turned to unusual surface states in the large class of non-symmorphic materials. In particular, KHgSb is predicted to exhibit double quantum spin Hall states. Here we report measurements of the Hall conductivity in KHgSb in a strong magnetic field B. In the quantum limit, the Hall conductivity is observed to fall exponentially to zero, but the diagonal conductivity is finite. A large gap protects this unusual zero-Hall state. We theoretically propose that, in this quantum limit, the chemical potential drops into the bulk gap, intersecting equal numbers of right- and left-moving quantum spin Hall surface modes to produce the zero-Hall state. The zero-Hall state illustrates how topological protection in a non-symmorphic material with glide symmetry may lead to highly unusual transport phenomena.
拓扑物质中一个反复出现的主题是通过对称性保护异常的电子态，例如，通过时间反演对称性保护Z拓扑绝缘体中的表面态。最近，人们的兴趣转向了一大类非对称材料中的异常表面态。特别是，预测KHgSb会表现出双量子自旋霍尔态。在此，我们报告了在强磁场B中对KHgSb的霍尔电导率的测量。在量子极限下，观察到霍尔电导率呈指数下降至零，但对角电导率是有限的。一个大的能隙保护了这种异常的零霍尔态。我们从理论上提出，在这个量子极限下，化学势落入体能隙，与数量相等的向右和向左移动的量子自旋霍尔表面模式相交，从而产生零霍尔态。零霍尔态说明了具有滑移对称性的非对称材料中的拓扑保护如何可能导致极其异常的输运现象。
