Spin Liquid State in theS=1/2Triangular LatticeBa3CuSb2O9

The synthesis and characterization of ${\mathrm{Ba}}_3{\mathrm{CuSb}}_2{\mathrm{O}}_9$, which has a layered array of ${\mathrm{Cu}}^{2+}$ spins in a triangular lattice, are reported. The magnetic susceptibility and neutron scattering experiments of this material show no magnetic ordering down to 0.2 K with a ${\theta }_{\mathrm{CW}}=-55\mathrm{K}$. The magnetic specific heat reveals a $T$-linear dependence with a $\gamma =43.4\mathrm{mJ}{\mathrm{K}}^{-2}{\mathrm{mol}}^{-1}$ below 1.4 K. These observations suggest that ${\mathrm{Ba}}_3{\mathrm{CuSb}}_2{\mathrm{O}}_9$ is a new quantum spin liquid candidate with a $S=1/2$ triangular lattice.