Witczak-Krempa William, Maciejko Joseph
Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1, Canada.
Phys Rev Lett. 2016 Mar 11;116(10):100402. doi: 10.1103/PhysRevLett.116.100402.
Topological states of electrons present new avenues to explore the rich phenomenology of correlated quantum matter. Topological insulators (TIs) in particular offer an experimental setting to study novel quantum critical points (QCPs) of massless Dirac fermions, which exist on the sample's surface. Here, we obtain exact results for the zero- and finite-temperature optical conductivity at the semimetal-superconductor QCP for these topological surface states. This strongly interacting QCP is described by a scale invariant theory with emergent supersymmetry, which is a unique symmetry mixing bosons and fermions. We show that supersymmetry implies exact relations between the optical conductivity and two otherwise unrelated properties: the shear viscosity and the entanglement entropy. We discuss experimental considerations for the observation of these signatures in TIs.
电子的拓扑态为探索关联量子物质丰富的现象学提供了新途径。特别是拓扑绝缘体（TIs）提供了一个实验环境来研究无质量狄拉克费米子的新型量子临界点（QCPs），这些量子临界点存在于样品表面。在这里，我们得到了这些拓扑表面态在半金属 - 超导体量子临界点处零温和有限温度下的光学电导率的精确结果。这个强相互作用的量子临界点由具有涌现超对称性的标度不变理论描述，超对称性是一种独特的将玻色子和费米子混合的对称性。我们表明超对称性意味着光学电导率与另外两个不相关性质之间的精确关系：剪切粘度和纠缠熵。我们讨论了在拓扑绝缘体中观察这些特征的实验考虑因素。
