Pressure-induced coexistence of superconductivity and magnetism in organic conductors κ - (BEDT–TTF)2X

We study within a mean field theory the interplay between superconductivity and antiferromagnetism in κ-(ET)2X compounds. The hydrostatic or chemical pressure induces first-order phase transitions between superconducting, antiferromagnetic and mixed states in which superconductivity and antiferromagnetism coexist. In this work, we compare the pressure effects in experiments and nesting quality according to our calculations. We describe the κκ-phase of the organic conductors by a two-band model exhibiting nesting properties governed by the ratio t1t2. When we apply pressure in these compounds, we modify the Fermi surface shape and consequently the strength of the antiferromagnetic fluctuations depending on the nesting properties. Our theoretical description seems to explain various experimental data, for which, to our best knowledge, no clear theoretical interpretation has been given so far.