Weak-link Josephson Junctions Made from Topological Crystalline Insulators

Abstract

We report on the fabrication of Josephson junctions using the topological crystalline insulator Pb_{0.5}Sn_{0.5}Te as the weak link. The properties of these junctions are characterized and compared to those fabricated with weak links of PbTe, a similar material yet topologically trivial. Most striking is the difference in the ac Josephson effect: junctions made with Pb_{0.5}Sn_{0.5}Te exhibit a rich subharmonic structure consistent with a skewed current-phase relation. This structure is absent in junctions fabricated from PbTe. A discussion is given on the origin of this effect as an indication of novel behavior arising from the topologically nontrivial surface state.

Evidence of half-integer Shapiro steps originated from nonsinusoidal current phase relation in a short ballistic InAs nanowire Josephson junction

“…Otherwise, anomalies appear in the Shapiro steps. For example, the fractional steps have been experimentally observed [8][9][10][11][12][13][14] and theoretically studied [15][16][17] since the 1960s. There are some different origins of half-integer steps and one of the origins is the skewness of the CPR.…”

Giant fractional Shapiro steps in anisotropic Josephson junction arrays

“…Recent works, exploring topological weak links, have shown that a Shapiro map is a powerful representation of the response at a fixed RF frequency to obtain information regarding the weak link CΦR 10,11,38 . A Shapiro map traces the widths of the observed plateaus as a function of the AC drive amplitude and DC current bias.…”

“…To investigate the harmonic content of the current-phase relationship in these novel weak link materials, experiments relying on detecting the phase-locked response of a current driven Josephson junction when subjected to a high frequency radiation field of frequency, ν rf , have recently been used [10][11][12][13][14][15] . In case the weak link is characterized by a conventional sinusoidal current-phase relationship, this resonant response manifests itself as constant voltage plateaus, so called Shapiro steps, in the voltage versus current (VI)-characteristics of the junction at voltages V n = nΦ 0 ν rf , where n 2 Z and Φ 0 the fluxquantum 16 .…”

Fractional Shapiro steps in resistively shunted Josephson junctions as a fingerprint of a skewed current-phase relationship

“…A Shapiro map, which traces the width of the Shapiro plateaus as a function of the ac and dc drive of the system, is a very powerful tool to investigate the harmonic content of the C R in a variety of weak links. Examples include weak links, where the coupling between the superconducting banks is established by a normal metal; a topological insulator; and graphene [26][27][28][29][30]. As such, we will focus our attention on these types of experiments.…”