Probing the minigap in topological insulator-based Josephson junctions under radio frequency irradiation

TL;DR

This paper extends a contact-resistance measurement method to detect the minigap and Andreev bound states in topological insulator Josephson junctions under radio frequency irradiation, revealing how rf power influences the minigap.

Contribution

It generalizes the contact-resistance-measurement method to include rf irradiation effects and interprets the data using RSJ and BTK models, aiding Majorana physics studies.

Findings

Minigap broadens with increased rf power

Data aligns with RSJ and BTK theoretical models

Method useful for studying Majorana physics

Abstract

Recently, a contact-resistance-measurement method was developed to detect the minigap, hence the Andreev bound states (ABSs), in Josephson junctions constructed on the surface of three-dimensional topological insulators (3D TIs). In this work, we further generalize that method to the circumstance with radio frequency (rf) irradiation. We find that with the increase of rf power, the measured minigap becomes broadened and extends to higher energies, in a way similar to the rf power dependence of the outer border of the Shapiro step region. We show that the corresponding data of contact resistance under rf irradiation can be well interpreted by using the resistively shunted Josephson junction model (RSJ model) and the Blonder-Tinkham-Klapwijk (BTK) theory. Our findings could be useful when using the contact-resistance-measurement method to study the Majorana-related physics in topological insulator-based Josephson junctions under rf irradiation.