Classifying superconductivity in Moir\'e graphene superlattices

TL;DR

This study investigates the pairing symmetry of superconductivity in twisted bilayer graphene Moiré superlattices, finding evidence for s-wave and specific p-wave symmetries through analysis of critical fields and currents.

Contribution

It introduces a detailed analysis of pairing symmetries in Moiré graphene superlattices using critical field and current measurements, highlighting the likely dominance of s-wave and certain p-wave symmetries.

Findings

s-wave and specific p-wave symmetries are likely dominant

Superconducting parameters suggest possible two-band superconductivity

Further data needed to conclusively distinguish pairing symmetries

Abstract

Several research groups have reported on the observation of superconductivity in bilayer graphene structures where single atomic layers of graphene are stacked and then twisted at angles $\theta$ forming Moir\'e superlattices. The characterization of the superconducting state in these 2D materials is an ongoing task. Here we investigate the pairing symmetry of bilayer graphene Moir\'e superlattices twisted at $\theta$ = 1.05{\deg}, 1.10{\deg} and 1.16{\deg} for carrier doping states varied in the range of n=0.5-1.5 10^(12) cm^(-2) (where superconductivity can be realized) by analyzing the temperature dependence of the upper critical field Bc2(T) and the self-field critical current Jc(sf,T) within currently available models for single- and two-band s-, d-, p- and d+id-wave gap symmetries. Extracted superconducting parameters show that only s-wave and a specific kind of p-wave symmetries are likely to be dominant in bilayer graphene Moir\'e superlattices. More experimental data is required to distinguish between the s- and remaining p-wave symmetries as well as the suspected two-band superconductivity in these 2D superlattices.