Signatures of the order parameter of a superconducting adatom layer in magnetic field dependent quasiparticle interference

TL;DR

This paper investigates how quasiparticle interference patterns in 2D superconducting adatom layers can reveal the symmetry of the pairing function, aiding in understanding the superconducting mechanism.

Contribution

It introduces a method to distinguish superconducting order parameters in 2D lattices using QPI pattern analysis, highlighting differences caused by various pairing symmetries.

Findings

QPI patterns vary with different pairing symmetries.

Charge and order-parameter disorder produce distinguishable scattering signatures.

QPI analysis can identify the angular momentum of superconducting pairs.

Abstract

Experiments have observed superconductivity in atomically-thin metallic layers deposited on semiconducting substrates. As in any superconductor, it is important to determine the structure of the superconducting pairing function in order to reveal the mechanism responsible for superconductivity. To that end, we study the possible superconducting states of two-dimensional triangular lattices. We calculate the quasiparticle interference (QPI) patterns which would result from various nearest-neighbor pairing order parameters, and show how the QPI can be used to distinguish between those order parameters. The QPI patterns are the momentum-space representations of real-space local density-of-states fluctuations: the QPI signal at momentum $q$ reveals the strength of scattering processes at that momentum transfer. We show how characteristic differences between scattering from charge disorder (i.e. impurities) and from order-parameter disorder (i.e. vortices) can be used to identify the angular momentum of the superconducting pairs.