题目：Identifying exotic bound states using a metallic probe.

演讲人：吕博（特聘研究员）

报告时间：2022年3月11日 （星期五) 15：30-17：00

报告地点：在线报告(腾讯会议ID: 129 927 818）

摘要：

We study the conductance afforded by a normal-metal probe which is directly contacting the helical edge modes of a quantum spin Hall insulator (QSHI). We show a quantized conductance peak in QSHI-based superconductor–ferromagnet hybrids due to the formation of a single Majorana bound state (MBS). In a corresponding Josephson junction hosting a pair of MBSs, quantized conductance peak is also found. The conductance quantization is robust to changes of the relevant system parameters and, remarkably, remains unaltered with increasing the distance between probe and MBSs. Our findings can therefore provide an effective way to detect the existence of MBSs in QSHI systems.  Furthermore, we theoretically study the effect of orbital-dependent exchange field in the formation of second order topological superconductors. We demonstrate that changing the orbital difference can induce topological transition and the Majorana corner modes therein can be manipulated. We use a normal probe terminal to detect the corner modes within the same scheme. To confirm the robustness of conductance peak arising from Majorana states, we study the influence of nonmagnetic impurity scatterings on the tunneling conductance of a junction consisting of a normal metal and a disordered unconventional superconductor by solving the quasiclassical Eilenberger equation self-consistently. We find that the impurity scatterings in both the Born and the unitary limits affect the formation of the Andreev bound states and modify strongly the tunneling spectra around zero bias. Our results are interpreted well by the appearance of odd-frequency Cooper pairs near the interface and by the divergent behavior of the impurity self-energy. The present paper provides a useful tool to identify the pairing symmetry of unconventional superconductors in experiments.

演讲人简介：

南开大学本科，北京大学博士，先后在名古屋大学，曼彻斯特大学国家石墨烯研究中心做博士后研究。2018年入职天津大学。现为量子中心特聘研究员。目前研究方向为超导近邻效应。

参考文献：

[1] Bo Lu, Yiying Zhang, Tunable Majorana corner modes by orbital-dependent exchange interaction in a two-dimensional topological superconductor, arXiv: 2203.02879 (2022).

[2] Bo Lu, Guanxin Cheng, Pablo Burset, Yukio Tanaka, Identifying Majorana bound states at quantum spin Hall edges using a metallic probe, arXiv:2110.04472 (2021).

[3]  Bo Lu, Pablo Burset, Yasunari Tanuma, Alexander A. Golubov, Yasuhiro Asano, and Yukio Tanaka,  Influence of the impurity scattering on charge transport in unconventional superconductor junctions, PHYS. REV. B 94, 014504 (2016).