Evidence of Chiral Order in the Charge-Ordered Phase of Superconducting La1.875Ba0.125Cuo4 Single Crystals Using Polar Kerr-Effect Measurements

TL;DR

This study uses polar Kerr effect measurements to detect chiral order in La1.875Ba0.125CuO4 crystals, revealing a universal gyrotropic order in the pseudogap phase of cuprate superconductors.

Contribution

It provides experimental evidence of chiral gyrotropic order in the charge-ordered phase of a cuprate superconductor, suggesting universality in the pseudogap regime.

Findings

Finite Kerr signal appears below charge ordering temperature

Kerr signal sign cannot be trained with magnetic field

Kerr signal is odd with respect to strain

Abstract

High resolution polar Kerr effect (PKE) measurements were performed on La1.875Ba0.125Cuo4 single crystals revealing that a finite Kerr signal is measured below an onset temperature-T_K that coincides with charge ordering transition temperature T_{CO}. We further show that the sign of the Kerr signal cannot be trained with magnetic field, is found to be the same of opposite sides of the same crystal, and is odd with respect to strain in the diagonal direction of the unit cell. These observations are consistent with a chiral "gyrotropic" order above T_c for La1.875Ba0.125Cuo4; similarities to other cuprates suggest that it is a universal property in the pseudogap regime.