# Gapless spin-liquid state in the structurally disorder-free triangular antiferromagnet NaYbO$_2$

## TL;DR

This paper reports the discovery of a gapless spin-liquid state in the disorder-free triangular antiferromagnet NaYbO$_2$, characterized by persistent spin dynamics and continuous magnetic excitations, providing a rare experimental realization of such a phase.

## Contribution

It demonstrates that NaYbO$_2$ is a structurally disorder-free material exhibiting a gapless spin-liquid state, offering direct experimental access to triangular antiferromagnet spin-liquid physics.

## Key findings

- No structural disorder or crystal-electric-field randomness in NaYbO$_2$
- Absence of magnetic order down to 70 mK
- Presence of gapless, continuous magnetic excitations at the K-point

## Abstract

We present the structural characterization and low-temperature magnetism of the triangular-lattice delafossite NaYbO$_2$. Synchrotron x-ray diffraction and neutron scattering exclude both structural disorder and crystal-electric-field randomness, whereas heat-capacity measurements and muon spectroscopy reveal the absence of magnetic order and persistent spin dynamics down to at least 70\,mK. Continuous magnetic excitations with the low-energy spectral weight accumulating at the $K$-point of the Brillouin zone indicate the formation of a novel spin-liquid phase in a triangular antiferromagnet. This phase is gapless and shows a non-trivial evolution of the low-temperature specific heat. Our work demonstrates that NaYbO$_2$ practically gives the most direct experimental access to the spin-liquid physics of triangular antiferromagnets.