Selection rules for quasiparticle interference with internal nonsymmorphic symmetries

TL;DR

This paper explores how nonsymmorphic symmetries influence quasiparticle interference patterns in STM measurements, revealing universal constraints and selection rules that can help interpret experimental data in complex materials.

Contribution

It introduces a theoretical framework linking nonsymmorphic symmetries to QPI selection rules, applicable to layered and rod group materials, and demonstrates this with specific material examples.

Findings

QPI maps encode universal symmetry information.

Absence or intensity of QPI signals reveal symmetry constraints.

Application to ZrSiS and TaAs illustrates the theory's relevance.

Abstract

We study how nonsymmorphic symmetries that commute with lattice translations are reflected in the quasiparticle interference (QPI) maps measured by scanning tunneling microscopy (STM). QPI maps, which result from scattering of Bloch states off impurities, record the interference of incoming and scattered waves as a function of energy and tip's position. Although both the impurity and the tip generically break spatial symmetries, we find that the QPI maps provide universal information on these symmetries. The symmetries impose constraints on the relation between various momentum components of the Bloch functions. These relations result in selection rules on certain momentum transfers in QPI maps. We find that universal information is encoded in the absence of QPI signal, or in the relative intensity of its replications. We show examples for one-dimensional chains and an effective model of the layered compound $\rm ZrSiS$. We discuss the implications of our theory in the analysis of observed QPI of the Weyl semimetal $\rm TaAs$. Our theory is particularly relevant for materials in rod and layer space groups, or when a correlated order parameter, such as antiferromagnetism, enlarges the unit cell.