Cu nuclear magnetic resonance study of charge and spin stripe order in La$_{1.875}$Ba$_{0.125}$CuO$_4$

TL;DR

This study uses Cu NMR to investigate charge and spin stripe order in La$_{1.875}$Ba$_{0.125}$CuO$_4$, revealing magnetic fluctuations cause signal wipeout and providing new insights into stripe dynamics and universality.

Contribution

It provides the first observation of the full Cu NMR signal in the stripe-ordered phase, confirming magnetic fluctuations as the cause of signal wipeout and analyzing spin and charge dynamics.

Findings

Spin-spin and spin-lattice relaxation rates are strongly enhanced in the charge ordered phase.

Magnetic fluctuations, not charge fluctuations, cause the wipeout effect.

Charge order is incommensurate with a universal amplitude across cuprates.

Abstract

We present a Cu nuclear magnetic/quadrupole resonance study of the charge stripe ordered phase of LBCO, with detection of previously unobserved ('wiped-out') signal. We show that spin-spin and spin-lattice relaxation rates are strongly enhanced in the charge ordered phase, explaining the apparent signal decrease in earlier investigations. The enhancement is caused by magnetic, rather than charge fluctuations, conclusively confirming the long-suspected assumption that spin fluctuations are responsible for the wipeout effect. Observation of the full Cu signal enables insight into the spin and charge dynamics of the stripe-ordered phase, and measurements in external magnetic fields provide information on the nature and suppression of spin fluctuations associated with charge order. We find glassy spin dynamics, in agreement with previous work, and incommensurate static charge order with charge modulation amplitude similar to other cuprate compounds, suggesting that the amplitude of charge stripes is universal in the cuprates.