Detection of a Disorder-Induced Bose-Einstein Condensate in a Quantum Spin Material at High Magnetic Fields

TL;DR

This study reveals a disorder-induced ordered phase in a doped quantum spin material under high magnetic fields, demonstrating a resurgence of quantum coherence from localized impurity states, confirmed by experiments and simulations.

Contribution

It uncovers a novel disorder-induced ordered state in a doped quantum spin chain, supported by experimental NMR data and quantum Monte Carlo simulations.

Findings

Identification of a new disorder-induced ordered phase.

Experimental phase diagram matches theoretical predictions.

Observation of quantum coherence resurgence from localized states.

Abstract

The coupled spin-1 chains material NiCl$_2$-4SC(NH$_2$)$_2$ (DTN) doped with Br impurities is expected to be a perfect candidate for observing many-body localization at high magnetic field: the so-called "Bose glass", a zero-temperature bosonic fluid, compressible, gapless, incoherent, and short-range correlated. Using nuclear magnetic resonance (NMR), we critically address the stability of the Bose glass in doped DTN, and find that it hosts a novel disorder-induced ordered state of matter, where many-body physics leads to an unexpected resurgence of quantum coherence emerging from localized impurity states. An experimental phase diagram of this new "order-from-disorder" phase, established from NMR $T_1^{-1}$ relaxation rate data in the (13 $\pm$ 1)% Br-doped DTN, is found to be in excellent agreement with the theoretical prediction from large-scale quantum Monte Carlo simulations.