Spin-correlation Driven Ferroelectric Quantum Criticality in a Perovskite Quantum Spin-liquid System, Ba3CuSb2O9

TL;DR

This study demonstrates spin-correlation-driven ferroelectric quantum criticality in Ba3CuSb2O9, revealing quantum paraelectric behavior and antiferromagnetic quantum critical fluctuations in a perovskite quantum spin-liquid system.

Contribution

First experimental observation of spin-correlation-driven ferroelectric quantum criticality in a perovskite quantum spin-liquid material.

Findings

Dielectric constant follows T2 scaling indicating quantum paraelectricity.

Inverse susceptibility exhibits T3/2 dependence, showing antiferromagnetic quantum critical fluctuations.

Strong spin-lattice interplay evidenced by spin, orbital, and lattice entanglement.

Abstract

Here we have experimentally demonstrated spin-correlation-driven ferroelectric quantum criticality in a prototype quantum spin-liquid system, Ba3CuSb2O9, a quantum phenomenon rarely observed. The dielectric constant follows a clear T2 scaling, showing that the material behaves as a quantum paraelectric without developing ferroelectric order. Magnetically, the system avoids long-range order down to 1.8 K and instead displays a T3/2 dependence in its inverse susceptibility, a hallmark of antiferromagnetic quantum critical fluctuations. Together with known spin-orbital-lattice entanglement in this compound, these signatures point to a strong interplay between spin dynamics and the polar lattice. Our pioneering work places this perovskite spin-liquid family at the forefront of this domain and suggest the flexibility of this family in a suitable environment by tuning chemical/ external pressure.