Possible gapless spin liquid in a rare-earth kagom\'{e} lattice magnet Tm$_{3}$Sb$_{3}$Zn$_{2}$O$_{14}$

TL;DR

This study provides evidence for a possible gapless spin liquid state in Tm$_{3}$Sb$_{3}$Zn$_{2}$O$_{14}$, a rare-earth kagome lattice magnet, through thermodynamic and muon spin relaxation measurements showing no magnetic order and a linear specific heat at low temperatures.

Contribution

It is the first to suggest a gapless spin liquid in a non-Cu rare-earth kagome system, highlighting the role of non-Kramers doublets in such quantum states.

Findings

No magnetic order down to 0.35 K.

Linear temperature dependence of specific heat at low T.

Suppression of a broad hump in specific heat under magnetic field.

Abstract

We report the thermodynamic and muon spin relaxation ($\mu$SR) evidences for a possible gapless spin liquid in Tm$_{3}$Sb$_{3}$Zn$_{2}$O$_{14}$, with the rare-earth ions Tm$^{3+}$ forming a two-dimensional kagom\'{e} lattice. We extract the magnetic specific heat of Tm$_{3}$Sb$_{3}$Zn$_{2}$O$_{14}$ by subtracting the phonon contribution of the non-magnetic isostructural material La$_{3}$Sb$_{3}$Zn$_{2}$O$_{14}$. We obtain a clear linear-$T$ temperature dependence of magnetic specific heat at low temperatures, with the heat-capacity coefficient $\gamma$ = 26.6(1) mJ mol-Tm$^{-1}$ K$^{-2}$ in the zero temperature limit. No long-range magnetic order was observed down to 0.35 K in the heat capacity measurement. A broad hump around 9 K was observed in the zero field magnetic specific heat and is gradually suppressed in the magnetic fields that also create a spin gap in the specific heat. The absence of magnetic order is further confirmed by the $\mu$SR measurement down to 20 mK. We find that the spin-lattice relaxation time remains constant down to the lowest temperatures. We point out that the physics in Tm$_{3}$Sb$_{3}$Zn$_{2}$O$_{14}$ is fundamentally different from the Cu-based herbertsmithite and propose spin liquid ground states with non-Kramers doublets on the kagom\'{e} lattice to account for the experimental results.