Bose glass behavior in (Yb$_{1-x}$Lu$_x$)$_4$As$_3$ representing the randomly diluted quantum spin-1/2 chains

TL;DR

This study investigates the Bose-glass phase in a diluted quantum spin chain compound, revealing field-dependent disorder effects and contrasting behavior with pure systems through specific heat measurements.

Contribution

It provides experimental evidence of Bose-glass behavior in a site-diluted quantum antiferromagnetic chain, highlighting the effects of quenched disorder and finite-size segments.

Findings

Observation of non-exponential low-temperature specific heat decay in diluted samples.

Identification of thermodynamic scaling consistent with Bose-glass phase.

Contrast with pure Yb$_4$As$_3$ showing gap opening.

Abstract

The site-diluted compound (Yb$_{1-x}$Lu$_x$)$_4$As$_3$ is a scarce realization of the linear Heisenberg antiferromagnet partitioned into finite-size segments and is an ideal model compound for studying field-dependent effects of quenched disorder in the one-dimensional antiferromagnets. It differentiates from the systems studied so far in two aspects - the type of randomness and the nature of the energy gap in the pure sample. We have measured the specific heat of single-crystal (Yb$_{1-x}$Lu$_x$)$_4$As$_3$ in magnetic fields up to 19.5 T. The contribution $C_{\perp}$ arising from the magnetic subsystem in an applied magnetic field perpendicular to the chains is determined. Compared to pure Yb$_4$As$_3$, for which $C_{\perp}$ indicates a gap opening, for diluted systems a non-exponential decay is found at low temperatures which is consistent with the thermodynamic scaling of the specific heat established for a Bose-glass phase.