Topic: Optical Responses of Chiral Majorana Modes

Speaker: Dr. Jun He (Riken)

Host: Professor Liu Tao

Presentation time: 3:00 PM, Tuesday, January 4, 2022

Venue: Conference room 220, 2 / F, Physics Building (Building 18)

Welcome to join us!

School of Physics and Optoelectronics

December 28, 2021

Report Summary: Majorana fermions exist on the boundaries of two-dimensional topological superconductors (TSCs) as charge-neutral quasiparticles. The neutrality makes the detection of such states challenging from both experimental and theoretical points of view. Current methods largely rely on transport measurements in which Majorana fermions manifest themselves by inducing electron-pair tunneling (Andreev reflection) at the lead-contacting point. In this talk, I will discuss alternative detecting methods --- by shining light.

I will show that chiral Majorana fermions in TSCs generate local optical responses. This results in a local optical conductivity that is proportional to when the photon frequency is small [1]. The features of the distinguish chiral Majorana fermions not only from trivial superconductors or insulators (where , but also from normal fermion edge states such as those in quantum Hall systems (where ). Then we further discuss the optical responses of chiral Majorana modes in Kitaev model of quantum spin liquids (QSLs), where the optical signal can be detected locally by Raman spectroscopy[2] since the Raman scattering intensity is proportional to , where is the Raman frequency shift.

References:

[1] James Jun He, Yukio Tanaka, and Naoto Nagaosa, Phys. Rev. Lett. 126, 237002 (2021).

[2] James Jun He, and Naoto Nagaosa, Phys. Rev. B 103, L241109 (2021).

Dr. Jun He graduated from the Department of Physics, Hong Kong University of Science and Technology in 2017 under the tutelage of Professor K. T. Law. After graduation, he worked as a postdoctoral research fellow in Naoto Nagaosa's Research group at RIKEN's Center for Emergent Matter Science (OR CEMS), where he conducted theoretical research on condensed Matter physics. The main research areas include topological superconductivity and Majorana Fermions, non-centrosymmetric superconductivity, Josephson junction, Ising superconductor, superconducting diode effect and so on. He has published 5 papers in Physical Review Letters (3) and Nature Communications (2) as co-first author. She has published 13 papers in academic journals such as Physical Review B and Communications Physics.