α- And β-(Bedt-TTF)₂I₃ – Two Modifications With Contrasting Groundstate Properties: Insulator and Volume Superconductor

Spin excitations in the quasi-two-dimensional charge-ordered insulatorα−(BEDT−TTF)2I3probed viaIshikawa1, Hirata2, Liu3 et al. 2016Phys. Rev. B

“…It has been revealed that this feature is characteristic for the high-energy part of the DF-type excitations in a tilted Dirac-cone system like -I3 [8][9][10][11][12]. However, the presence of the low-energy linear spectrum near EF is hidden at low T beneath the first-order chargeordering (CO) transition taking place at TCO ≈ 135K [1,3,[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] due to strong electron correlations [28,29]. The transition is accompanied by an opening of an energy gap in the charge and spin excitation spectra and a formation of quasi-one-dimensional (quasi-1D) charge stripes along the crystalline b axis [14], leading to an insulating spin-singlet ground state [1,3,17,18,20,30,31].…”

“…Gaining deeper knowledge on the nature of spin excitations in this 2D system naturally requires further theoretical studies by taking into account the realistic values for both of the on-site and nearest neighbor Coulomb repulsions, which are not explicitly considered here. It is an interesting future issue to see how the sizes of these gaps as well as the ratio R/S vary on increasing P and thereby suppressing TCO [3,19,20].…”

Crossover from Positive to Negative Interlayer Magnetoresistance in Multilayer Massless Dirac Fermion System with Non-Vertical Interlayer Tunneling

“…[10][11][12][13] This metal-insulator transition is suppressed by applying pressure. 14,15) Under pressure larger than ∼ 2GPa, the system is metallic and the resistivity is almost temperature independent while the Hall coefficient shows strong temperature dependences. 16) Kobayashi et al calculated the energy dispersion 6, 7) using the tight-binding model.…”

Pressure-dependent optical investigations ofα−(BEDT-TTF)2I3: Tuning charge order and narrow gap towards a Dirac semimetal

“…10 The application of pressure gradually shifts the metal-insulator transition and the system remains metallic down to lowest temperatures. [11][12][13] The nature of this state as well as the detailed mechanism driving the transitions, however, are far from being fully understood.…”