TITLE: "Interplay between magnetism and superconductivity in 2-d organic superconductors"

SPEAKER: Professor Yuri Sushko,

TIME: Thursday Mar. 29, 2001 at 4 PM

PLACE: George P. Williams, Jr. Lecture Hall, (Olin 101)

Organic salts based on BEDT-TTF {bis(ethylenedithio)tetrathiafulvalene} molecule comprise quite a large family of quasi-2-dimensional superconductors. In this family, a network of covalently bonded BEDT-TTF donor molecules form two-dimensional conducting layers separated by insulating layers of the polymeric anions such as X=Cu[N(CN)₂]Br, X = Cu(NCS)₂ and X = Cu[N(CN)₂]Cl. The metallic conduction within the BEDT-TTF sheets is due to the intermolecular bonding between BEDT-TTF donors and the partial charge transfer between the donors and the anions. In this talk, I will present pressure-temperature phase diagram of the 13K superconductors kappa-(BEDT-TTF)₂Cu[N(CN)₂]Cl_1-xBr_x which reveals very delicate balance between a magnetic insulator state and a superconducting state, with pronounced pressure-, structure/composition-, and even cooling rate dependencies. Possible mechanisms of strong interplay between two antagonistic states are discussed in connection to the reduced dimensionality of the electronic structure typical for (BEDT-TTF) salts.