Uniaxial strain induced superconductivity in quantum spin liquid κ-(ET)₂Ag₂(CN)₃

We investigate the uniaxial strain effects on the quantum spin liquid κ-(ET)₂Ag₂(CN)₃ which is an organic Mott insulator with a nearly regular S = 1/2 triangular lattice. The uniaxial compressive strains along the in-plane b- and c-axes suppress the semiconducting behavior and induce a Mott transition, followed by a superconducting transition at low temperatures. The simulations of band structure under the in-plane uniaxial strains suggest a significant distortion of triangular lattice. The critical temperature T_C of the superconducting transition appeared above the critical pressure of Mott transition under uniaxial strain is higher than that under hydrostatic pressure as observed in the sister compound κ-(ET)₂Cu₂(CN)₃. The enhancement of T_C by the distortion of triangular lattice is a common feature of superconductivity neighboring to spin liquid. (author)