Magnetic-impurity resonance states for different pairing symmetries in twisted bilayer graphene

TL;DR

This paper investigates magnetic-impurity resonance states in the superconducting phase of twisted bilayer graphene, revealing how impurity location and pairing symmetry influence resonance patterns and providing evidence for non-$s$-wave pairing.

Contribution

It analyzes the effects of impurity position on resonance states in twisted bilayer graphene for various pairing symmetries using a two-orbital model.

Findings

Resonance state distributions break $D_3$ symmetry depending on pairing symmetry.

Resonance peaks near impurities suggest non-$s$-wave pairing.

Impurity location significantly affects resonance patterns.

Abstract

In this work, we study the magnetic-impurity resonance states in superconducting phase of twisted bilayer graphene for different pairing symmetries. Using the two-orbital model proposed by Yuan and Fu in [Phys. Rev. B 98, 045103 (2018)], we find that when the impurity is located at one site of the emergent honeycomb lattice, the spacial distributions of the resonance states will break both the threefold and twofold rotation symmetries of $D_3$ group for pairing symmetries which belong to the irreducible representations of this point group. When the magnetic impurity is located at the center of the emergent honeycomb lattice, the appearance of resonance peak at the position close to the impurity can be considered as a strong evidence of non-$s$-wave pairing.