Uniaxial strain effects on mott and superconducting transitions in κ-(ET)_2Cu_2(CN)_3

摘要

We have investigated the anisotropic modulation of a triangular lattice in the spin-liquid Mott insulator κ-(ET)_2Cu_2(CN) _3 exhibiting Mott transition accompanied by superconducting transition. Under uniaxial strain along each crystal axis, the superconducting transition temperature Tc plotted against the insulator-metal crossover temperature TIM increases. An increase in the superconducting upper critical field confirms the increase in Tc under inplane uniaxial strain. The result is distinct from the abrupt monotonic decrease in Tc under hydrostatic pressure, indicating that electron correlation cannot be the primary origin of the enhancement of Tc. We discuss uniaxial strain effects on the basis of the quadratic temperature dependence of resistivity and the results of band structure calculation.