Mott transition and superconductivity in the strongly correlated organic superconductorκ−(BEDT−TTF)2Cu[N(<

Abstract

The magnetic field effect on the phase diagram of the organic Mott system κ-(BEDT-TTF)2Cu[N(CN)2]Br in which the bandwidth was tuned by the substitution of deuterated molecules was studied by means of the resistivity measurements performed in magnetic fields. The lower critical point of the first-order Mott transition, which ended on the upper critical field Hc2-temperature plane of the superconductivity, was determined experimentally in addition to the previously observed upper critical end point. The lower critical end point moved to a lower temperature with the suppression of Tc in magnetic fields and the Mott transition recognized so far as the S-shaped curve reached T = 0 when H > Hc2 in the end.PACS numbers: 74.70. Kn, 71.30.+h, 74.25.Dw Metal-insulator (MI) transitions have been one of the central issues in strongly correlated electron systems. Among the various types of MI transitions, the Mott transition is the most attractive phenomenon, which arises from an electron-electron interaction in a wide range of materials.1 Mott insulator derives from a large electrical Coulomb repulsion energy U with respect to the bandwidth W . Metal transitions can occur in two ways in a Mott insulator: one can change the strength of the interaction U/W , while maintaining the required bandfilling value and is referred to as a bandwidth-controlled Mott transition or one can introduce carriers with the required density, while maintaining U/W and is referred to as a band-filling-controlled Mott transition. The former case occurs, for example, in vanadium oxides and molecular conductors, while the latter occurs in high-T c cuprate superconductors.Organic charge transfer salts based on the donor molecule bis(ethylenedithio)-tetrathiafulvalene, abbreviated as BEDT-TTF or ET, have been recognized as a highly correlated electron system.2 Among them, κ-(ET) 2 X with X = Cu(NCS) 2 , Cu[N(CN) 2 ]Y (Y = Br and Cl), etc. has attracted considerable attention due to its strongly correlated quasi-two-dimensional electron system because the strong dimer structure consisting of two ET molecules makes the conduction band half filled.3,4 Furthermore, the softness of the lattice in molecular conductors enables us to easily modulate the bandwidth by applying small physical and chemical pressures, while maintaining the band-filling. Therefore, the κ-(ET) 2 X system has been considered to be one of the typical bandwidth-controlled Mott systems.The first-order Mott transition characterized by an Sshaped curve induces the correlated metal and superconductor phases from the Mott insulator phase by applying a small helium gas pressure or by the slight molecular substitution of the donor or anion molecules. 3,5,6,7,8 The relation and transitions among the various phases in the phase diagram have been studied extensively, both experimentally and theoretically. Several unique features have been found in association with the Mott transition. The first-order transition is terminated at T U cr ≃ 32- 40 K 6,8,9 , which is the upper critical end poin...

Superconducting state coexisting with a phase-separated static magnetic order in(Ba,K)Fe2As2,Goko1, Aczel2, Baggio-Saitovitch3 et al. 2009Phys. Rev. B1396841View full textAdd to dashboardCite

“…Phase separation at the border of magnetic and superconducting states has been found also in the organic ͑BEDT-TTF͒ 2 -X superconductors 39 and CeCu 2 Si 2 . 40 Firstorder phase transitions, similar to those in the La1111 FeAs system, 19 have been found in the A 3 C 60 , 41 Ce͑Co, Cd͒In 5 , and CeRhIn 5 ͑Ref.…”

Half-filled Hubbard model on a Bethe lattice with next-nearest-neighbor hopping

“…Very interesting examples for frustrated systems are layered organic compounds such as -͑BEDT-TTF͒2X. [4][5][6][7][8][9][10][11][12][13][14][15][16][17] They have a similar phase diagram as the high-temperature superconductors ͑HTSCs͒. 18 The phases of these organic systems are controlled by pressure and frustration rather than by doping as in HTSC.…”

Spatial mapping of electronic states in κ-(BEDT-TTF)2X using infrared reflectivity

“…On the strong correlation side, the bad metal becomes a Mott insulator at T ins and then becomes an antiferromagnetic Mott insulator at T N . Applied magnetic field suppresses the superconducting phase and extends the Mott insulating phase to the good-metal phase [26,27]. Thus, the κ-(BEDT-TTF) 2 X family was considered a bandwidth-controlled Mott system in contrast to the filling-controlled system in inorganic perovskites, such as high-T c copper oxides.…”