Measurement of low energy charge correlations in underdoped spin-glass La-based cuprates using impedance spectroscopy

TL;DR

This study investigates low energy charge dynamics in underdoped La-based cuprates using impedance spectroscopy, revealing slow charge fluctuations sensitive to doping, temperature, and crystallographic direction, with differences between Li and Sr doping.

Contribution

It provides new insights into charge kinetics and spatial charge segregation in lightly doped cuprates, highlighting the impact of different dopants on charge and spin dynamics.

Findings

Charge dynamics slow down with decreasing temperature.

Charge carriers in Sr-doped samples form dynamic segregated domains.

Charge and spin dynamics exhibit different temperature dependencies.

Abstract

We report on the charge kinetics of La_2CuO_4 lightly doped with Li and Sr. Impedance spectroscopy measurements down to 25mK and from 20Hz to 500kHz reveal evidence for low energy charge dynamics, which slow down with decreasing temperature. Both systems are acutely sensitive to stoichiometry. In the case of Sr substitution, which at higher carrier concentration evolves to a high temperature superconductor, the ground state in the pseudogap-doping regime is one of spatially segregated, dynamic charge domains. The charge carriers slow down at substantially lower temperatures than their spin counterparts and the dynamics are particularly sensitive to crystallographic direction. This is contrasted with the case of Li-doping.