Quantum melting of the hole crystal in the spin ladder of Sr14-xCaxCu24O41

TL;DR

This study investigates the quantum melting of the hole crystal in a spin ladder system, revealing how doping and temperature influence charge order and suggesting topological defects as a melting mechanism.

Contribution

It provides experimental evidence of charge density wave behavior and its quantum melting in a doped spin ladder, highlighting the role of discommensuration and topological defects.

Findings

Hole crystal forms only at specific commensurate wave vectors.

Temperature scaling of the hole crystal follows a simple ratio.

Charge order melts for irrational wave vectors, possibly via fractional charge defects.

Abstract

The "spin ladder" is a reduced-dimensional analogue of the high temperature superconductors that was predicted to exhibit both superconductivity and an electronic charge density wave or "hole crystal" (HC). Both phenomena have been observed in the doped spin ladder system Sr14-xCaxCu24O41 (SCCO), which at x=0 exhibits a HC which is commensurate at all temperatures. To investigate the effects of discommensuration we used resonant soft x-ray scattering (RSXS) to study SCCO as a function of doped hole density, d. The HC forms only with the commensurate wave vectors L_L = 1/5 and L_L = 1/3 and exhibits a simple temperature scaling T_(1/3) / T_(1/5) = 5/3. For irrational wave vectors the HC "melts", perhaps through the motion of topological defects carrying fractional charge.