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Quasi-two-dimensional organic superconductors: A review

“…Figure 3 shows another BEDT-TTF charge-transfer salt, β-(BEDT-TTF) 2 I 3 (again β denotes the packing arrangement of the BEDT-TTF molecules) [18]. As in the case of κ-(BEDT-TTF) 2 Cu(NCS) 2 (Figure 2), the BEDT-TTF molecules pack in planes separated by layers of the smaller anions, in this case I 3 molecules. However, the packing arrangement of the BEDT-TTF molecules is considerably different from that in κ-(BEDT-TTF) 2 Cu(NCS) 2 .…”

“…YBa 2 Cu 3 O 7 ) which have been the subject of considerable experimental and theoretical effort. Organic metals share many features with the cuprates-a quasi-two-dimensional bandstructure, the proximity of antiferromagnetism, superconductivity and insulating behaviour, unconventional superconductivity [1,2,3,4,5]-and yet they are much cleaner systems; it has been possible to measure many details of the electronic energy levels of the organics using accurate techniques [1,6], whereas this has proved impossible in the cuprates. Finally, the organics are interesting because a variety of exotic phases have been predicted and measured at potentially accessible magnetic fields (B ∼ 50 − 100 T) and temperatures [7,8,9].…”

Pairing and Superconductivity Driven by Strong Quasiparticle Renormalization in Two-Dimensional Organic Charge Transfer Salts

“…While the low-T susceptibility is suppressed, consistent with the opening of a spin gap, the observed power-law dependence, 1/T 1 ∝ T 2 , of the NMR-spin liquid relaxation rate[3] supports gapless (possibly nodal) excitations of the spin liquid. Under pressure, κ-(ET) 2 Cu 2 (CN) 3 becomes, like many similar κ-(ET) 2 X systems [4,5,6], a superconductor [7].In quasi two-dimensional κ-(ET) 2 X salts [4,5,6] dimers of ET = bis[ethylenedithio]-tetrathiafulvalene molecules are arranged in an anisotropic triangular lattice, with a charge state of one hole per dimer. The insulating state is, in most cases, antiferromagnetically ordered and separated from a pressure induced superconducting phase by a first order transition [8].…”

“…While the low-T susceptibility is suppressed, consistent with the opening of a spin gap, the observed power-law dependence, 1/T 1 ∝ T 2 , of the NMR-spin liquid relaxation rate [3] supports gapless (possibly nodal) excitations of the spin liquid. Under pressure, κ-(ET) 2 Cu 2 (CN) 3 becomes, like many similar κ-(ET) 2 X systems [4,5,6], a superconductor [7].…”

“…In quasi two-dimensional κ-(ET) 2 X salts [4,5,6] dimers of ET = bis[ethylenedithio]-tetrathiafulvalene molecules are arranged in an anisotropic triangular lattice, with a charge state of one hole per dimer. The insulating state is, in most cases, antiferromagnetically ordered and separated from a pressure induced superconducting phase by a first order transition [8].…”