Experimental Evidence for a Glass forming "Stripe Liquid" in the Magnetic Ground State of La1.65Eu0.2Sr0.15CuO4

TL;DR

This study provides experimental evidence for a glass-forming 'stripe liquid' state in the magnetic ground state of La1.65Eu0.2Sr0.15CuO4, characterized by diverging spin fluctuation times and intrinsic magnetic freezing.

Contribution

It demonstrates the existence of a glass-forming 'charge stripe liquid' in La1.65Eu0.2Sr0.15CuO4's magnetic ground state through NMR measurements and analysis of spin dynamics.

Findings

Dramatic slowing of Cu 3d spins below 30 K.

Diverging fluctuation time scale as (T - T_A)^(-1.9).

Intrinsic magnetic freezing indicative of a stripe liquid state.

Abstract

We report measurements of the longitudinal ($^{139}T_1^{-1}$) and transverse ($^{139}T_2^{-1}$) decay rates of the magnetization of $^{139}$La nuclei performed in a high quality single crystal of La$_{1.65}$Eu$_{0.2}$Sr$_{0.15}$CuO$_{4}$. We observe a dramatic slowing of the Cu 3d spins manifested as a sharp increase of both $^{139}T_1^{-1}$ and $^{139}T_2^{-1}$ below 30 K. We find that in this temperature range the fluctuations involve a unique time scale $\tau $ which diverges as $(T-T_{\rm A})^{-1.9}$ with $T_{\rm A}\thickapprox 5$ K. This behavior is distinct from the continuous freezing observed in underdoped La$_{1-x}$Sr$_x$CuO$_4$ which involves a distribution of energy barriers. By contrast, in La$_{1.65}$Eu$_{0.2}$Sr$_{0.15}$CuO$_{4}$, the freezing below 30K is intrinsic to its magnetic ground state and the observed power law supports the existence of a glass forming "charge stripe liquid".