NaYbS$_2$ - a new planar spin-$\frac{1}{2}$ triangular-lattice magnet and putative spin liquid

TL;DR

This study presents high-quality NaYbS$_2$ single crystals exhibiting quasi-2D anisotropic magnetism, strong spin-orbit entanglement, and no magnetic order down to very low temperatures, suggesting it as a promising candidate for a quantum spin liquid.

Contribution

The paper reports the synthesis and detailed characterization of NaYbS$_2$ as a new pure spin-1/2 triangular lattice magnet with potential quantum spin liquid behavior, contrasting with related materials.

Findings

NaYbS$_2$ shows no long-range magnetic order down to 260 mK.

The material exhibits strongly anisotropic quasi-2D magnetism.

Narrow ESR and NMR lines indicate absence of structural distortions.

Abstract

Platelike high-quality NaYbS$_{2}$ rhombohedral single crystals with lateral dimensions of a few mm have been grown and investigated in great detail by bulk methods like magnetization and specific heat, but also by local probes like nuclear magnetic resonance (NMR), electron-spin resonance (ESR), muon-spin relaxation ($\mu$SR), and inelastic neutron scattering (INS) over a wide field and temperature range. Our single-crystal studies clearly evidence a strongly anisotropic quasi-2D magnetism and an emerging spin-orbit entangled $S=1/2$ state of Yb towards low temperatures together with an absence of long-range magnetic order down to 260~mK. In particular, the clear and narrow Yb ESR lines together with narrow $^{23}$Na NMR lines evidence an absence of inherent structural distortions in the system, which is in strong contrast to the related spin-liquid candidate YbMgGaO$_{4}$ falling within the same space group $R\overline{3}m$. This identifies NaYbS$_{2}$ as a rather pure spin-1/2 triangular lattice magnet and a new putative quantum spin liquid.