Upper critical fields of pressurized organic superconductors κ-(BEDT-TTF)2X in the magnetic fields parallel to the layer

Abstract The upper critical fields in the direction parallel to superconducting plane, H c2 ″, of the layered salts κ-(BEDT-TTF) 2 X (X=Cu(NCS) 2 , Cu[N(CN) 2 ]Br) and κ-(BEDT-TTF) 4 -Hg 2.89 Br 8 far exceed the BCS Pauli paramagnetic limit and show variety of temperature ( T ) dependence at ambient pressure. We extended the studies of the H c2 ″( T ) diagrams for all main κ-(BEDT-TTF) 2 X superconductors by applying pressure. Emphasis is placed on the behaviour at low T and in high magnetic fields. The origin of the exceeding the BCS Pauli paramagnetic limit is discussed. The dependence of H c2 ″ on the field direction within the plane is also presented.