Department of Physics and Fribourg Center for Nanomaterials, University of Fribourg, Chemin du Musée 3, CH-1700 Fribourg, Switzerland.
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190, China.
Phys Rev Lett. 2018 Nov 2;121(18):187401. doi: 10.1103/PhysRevLett.121.187401.
We present an infrared spectroscopy study of ZrTe_{5}, which confirms a recent theoretical proposal that this material exhibits a temperature-driven topological quantum phase transition from a weak to a strong topological insulating state with an intermediate Dirac semimetal state around T_{p}≃138 K. Our study details the temperature evolution of the energy gap in the bulk electronic structure. We found that the energy gap closes around T_{p}, where the optical response exhibits characteristic signatures of a Dirac semimetal state, i.e., a linear frequency-dependent optical conductivity extrapolating to the origin (after subtracting a weak Drude response). This finding allows us to reconcile previous diverging reports about the topological nature of ZrTe_{5} in terms of a variation of T_{p} that depends on the crystal growth condition.
我们对 ZrTe_{5} 进行了红外光谱研究，证实了最近的理论预测，即在 138 K 左右的温度Tp，该材料从弱拓扑绝缘态到强拓扑绝缘态经历了一个温度驱动的拓扑量子相变，并有一个中间的狄拉克半金属态。我们的研究详细描述了体电子结构中能隙随温度的演化。我们发现，在Tp 附近能隙关闭，在那里光学响应表现出狄拉克半金属态的特征特征，即光学电导率随频率呈线性变化，并在原点处（减去弱的德劳德响应后）外推。这一发现使我们能够调和关于 ZrTe_{5} 的拓扑性质的先前相互矛盾的报告，这些报告是根据 Tp 的变化得出的，Tp 的变化取决于晶体生长条件。
