Evidence for a nematic phase in La$_{1.75}$Sr$_{0.25}$NiO$_{4}$

TL;DR

This paper provides evidence for a nematic phase in La$_{1.75}$Sr$_{0.25}$NiO$_{4}$ by demonstrating anisotropic charge stripe excitations, indicating electronic nematic order in a doped Mott insulator.

Contribution

The study presents neutron scattering evidence of anisotropic charge stripe excitations, revealing a nematic phase in La$_{1.75}$Sr$_{0.25}$NiO$_{4}$, advancing understanding of electronic states in doped Mott insulators.

Findings

Charge stripe excitations are anisotropic.

Evidence of electronic nematic order.

Supports the existence of a nematic phase in the material.

Abstract

Determining the nature of electronic states in doped Mott insulators remains a challenging task. In the case of tetragonal La$_{2-x}$Sr$_{x}$NiO$_{4}$, the occurrence of diagonal charge and spin stripe order in the ground state is now well established. In contrast, the nature of the high-temperature "disordered" state from which the stripe order develops has long been a subject of controversy, with considerable speculation regarding a polaronic liquid. Following on the recent detection of dynamic charge stripes, we use neutron scattering measurements on an $x=0.25$ crystal to demonstrate that the dispersion of the charge stripe excitations is anisotropic. This observation provides compelling evidence for the presence of electronic nematic order.