Electronic Liquid Crystal Physics of Underdoped Cuprates

TL;DR

This paper reviews evidence for intra-unit-cell nematic order in underdoped cuprates, its coupling to stripe fluctuations, analysis techniques, a microscopic mechanism, and open questions in the pseudogap phase.

Contribution

It provides a comprehensive review of intra-unit-cell nematic order in cuprates, including analysis methods, a phenomenological coupling theory, and a microscopic mechanism.

Findings

Evidence for long-range IUC nematic order in underdoped cuprates

Strong coupling between IUC nematic order and stripe fluctuations

A proposed microscopic mechanism driven by on-site and near-neighbor repulsions

Abstract

Recent observations of broken symmetries have partly demystified the pseudogap phase. Here we review evidence for long-range intra-unit-cell(IUC) nematic order and its unexpectedly strong coupling to the phase of the fluctuating stripes in the pseudogap states of underdoped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$. In particular, we focus on the analysis techniques that reveal this evidence in scanning tunneling spectroscopy data, the definition of the extracted IUC nematic order parameter, and a phenomenological theory of the coupling between the IUC nematic order and the previously reported coexisting fluctuating stripes. We also present a microscopic mechanism of IUC nematic order driven by on-site and near-neighbor repulsions. Finally we discuss open questions in the context of these results.