Detection of electronic nematicity using scanning tunneling microscopy

TL;DR

This paper demonstrates that apparent electronic nematicity observed in STM measurements can result from tunneling interference effects caused by tip structure, rather than true nematic order, offering a new method to probe quasiparticle momentum changes.

Contribution

The study reveals that STM tip-induced interference effects can mimic nematic signals, challenging previous interpretations and providing a novel approach to investigate quasiparticle band structures.

Findings

Interference effects cause energy-dependent symmetry-breaking in conductance maps.

Experimental confirmation of tip-induced artifacts in Bi-2212 and other systems.

Interference effects serve as a sensitive probe of quasiparticle momentum changes.

Abstract

Electronic nematic phases have been proposed to occur in various correlated electron systems and were recently claimed to have been detected in scanning tunneling microscopy (STM) conductance maps of the pseudogap states of the cuprate high-temperature superconductor Bi2Sr2CaCu2O8+x (Bi-2212). We investigate the influence of anisotropic STM tip structures on such measurements and establish, with a model calculation, the presence of a tunneling interference effect within an STM junction that induces energy-dependent symmetry-breaking features in the conductance maps. We experimentally confirm this phenomenon on different correlated electron systems, including measurements in the pseudogap state of Bi-2212, showing that the apparent nematic behavior of the imaged crystal lattice is likely not due to nematic order but is related to how a realistic STM tip probes the band structure of a material. We further establish that this interference effect can be used as a sensitive probe of changes in the momentum structure of the sample's quasiparticles as a function of energy.