Emergence of a Fluctuating Ground State in Y-kapellasite under Pressure

TL;DR

This study shows that applying pressure to Y-kapellasite suppresses magnetic order, leading to a dynamic ground state indicative of a quantum spin liquid, without structural changes.

Contribution

It demonstrates pressure-induced suppression of static magnetism and emergence of a fluctuating ground state in Y-kapellasite, a clean kagome system.

Findings

Static magnetism is fully suppressed at 2.3 GPa.

Pressure reduces kagome anisotropy, increasing magnetic frustration.

No structural transitions occur under pressure.

Abstract

Y-kapellasite (Y$_3$Cu$_9$(OH)$_{19}$Cl$_8$), which hosts an original anisotropic kagome sublattice, is a promising candidate for studying elusive and complex correlated physics. It exhibits a theoretically predicted in-plane $(1/3, 1/3)$ magnetic order [1] but its magnetic interaction values place it close to a phase boundary to a spin liquid state [2]. Our $\mu$SR measurements under hydrostatic pressure demonstrate the complete suppression of static magnetism in favor of a fully dynamical ground state at $2.3$~GPa. Complementary high-pressure x-ray and optical phonon measurements reveal a gradual reduction of the kagome anisotropy, enhancing magnetic frustration without structural transitions. Our results establish Y-kapellasite as a rare clean kagome model in which long-range order is suppressed by pressure-tuned frustration, the first fingerprint for the realization of a quantum spin liquid without strong disorder.