Field-tunable quantum disordered ground state in the triangular lattice antiferromagnet NaYbO$_2$

TL;DR

NaYbO$_2$ exhibits a quantum spin liquid ground state with no magnetic order down to 50 mK, which can be tuned into an ordered state with an applied magnetic field, making it a versatile platform for studying quantum magnetism.

Contribution

This work provides the first realization of a field-tunable quantum disordered ground state in an ideal triangular lattice antiferromagnet without site disorder.

Findings

No magnetic order observed down to 50 mK.

Presence of a two-peak specific heat indicating a quantum spin liquid.

Magnetic field induces a transition to a collinear ordered state.

Abstract

Antiferromagnetically coupled S=1/2 spins on an isotropic triangular lattice is the paradigm of frustrated quantum magnetism, but structurally ideal realizations are rare. Here we investigate NaYbO$_2$, which hosts an ideal triangular lattice of $J_{eff}=1/2$ moments with no inherent site disorder. No signatures of conventional magnetic order appear down to 50 mK, strongly suggesting a quantum spin liquid ground state. We observe a two-peak specific heat and a nearly quadratic temperature dependence in accord with expectations for a two-dimensional Dirac spin liquid. Application of a magnetic field strongly perturbs the quantum disordered ground state and induces a clear transition into a collinear ordered state consistent with a long-predicted up-up-down structure for a triangular lattice XXZ Hamiltonian driven by quantum fluctuations. The observation of spin liquid signatures in zero field and quantum-induced ordering in intermediate fields in the same compound demonstrate an intrinsically quantum disordered ground state. We conclude that NaYbO$_2$ is a model, versatile platform for exploring spin liquid physics with full tunability of field and temperature.