Possible quantum spin liquid state of CeTa${}_7$O${}_{19}$

Abstract

CeTa${}_7$O${}_{19}$ is a recently found two-dimensional triangular lattice antiferromagnet without showing magnetic order. We grew high-quality CeTa${}_7$O${}_{19}$ single crystals and studied the low-temperature magnetic susceptibility, specific heat and thermal conductivity. The dc magnetic susceptibility and magnetization reveal its nature of effective spin-1/2, easy axis anisotropy, and antiferromagnetic spin coupling. The ultralow-temperature ac susceptibility and specific heat data indicate the absence of any phase transition down to 20 mK. The ultralow-temperature thermal conductivity ($\hat{I}º$) at zero magnetic field exhibits a non-zero residual term $\hat{I}{º}_0/T=$ 0.0056 W/K${}^2$m. Although the magnetic field dependence of $\hat{I}º$ is rather weak, the 14 T thermal conductivity shows an essential zero residual term. All these results point to a possible ground state of quantum spin liquid.

8 pages, 6 figures, accepted for publication in Phys. Rev. B