Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou, 510006, China.
Sci Rep. 2017 Jun 21;7(1):3971. doi: 10.1038/s41598-017-04360-x.
We investigate the thermoelectric effect on a topological insulator surface with particular interest in impurity-induced resonant states. To clarify the role of the resonant states, we calculate the dc and ac conductivities and the thermoelectric coefficients along the longitudinal direction within the full Born approximation. It is found that at low temperatures, the impurity resonant state with strong energy de-pendence can lead to a zero-energy peak in the dc conductivity, whose height is sensitively dependent on the strength of scattering potential, and even can reverse the sign of the thermopower, implying the switching from n- to p-type carriers. Also, we exhibit the thermoelectric signatures for the filling process of a magnetic band gap by the resonant state. We further study the impurity effect on the dynamic optical conductivity, and find that the resonant state also generates an optical conductivity peak at the absorption edge for the interband transition. These results provide new perspectives for understanding the doping effect on topological insulator materials.
我们研究了拓扑绝缘体表面的热电效应，特别关注杂质诱导的共振态。为了阐明共振态的作用，我们在完全玻恩近似下沿着纵向方向计算了直流和交流电导率以及热电器件系数。结果表明，在低温下，具有强能量依赖性的杂质共振态会导致直流电导率中的零能峰，其高度对散射势的强度敏感依赖，甚至可以反转热功率的符号，这意味着从 n 型到 p 型载流子的转变。此外，我们还展示了共振态对填充磁性能带隙过程的热电特性。我们进一步研究了杂质对动态光学电导率的影响，发现共振态也会在带间跃迁的吸收边处产生一个光学电导率峰。这些结果为理解掺杂对拓扑绝缘体材料的影响提供了新的视角。
