Spin excitations in the quasi-two-dimensional charge-ordered insulatorα−(BEDT−TTF)2I3probed via

Kinzô Ishikawa

¹

,

Michihiro Hirata

²

,

Dong Liu

³

et al.

Abstract

The spin excitations from the nonmagnetic charge-ordered insulating state of -(BEDT-TTF)2I3 at ambient pressure have been investigated by probing the static and lowfrequency dynamic spin susceptibilities via site-selective nuclear magnetic resonance at 13

Optical Conductivity in a Two-Dimensional Extended Hubbard Model for an Organic Dirac Electron System α-(BEDT-TTF)2I3

“…An organic conductor α-(BEDT-TTF) 2 I 3 has attracted much interest, since it exhibits a transition between the charge order (CO) [1][2][3][4][5][6][7] and the massless Dirac electron (DE) [8][9][10][11][12][13][14][15] as hydrostatic pressure, P, increases. Recently, strong electron correlation effects have been revealed in both the CO [16] and the massless DE [17][18][19][20] in spin fluctuations.…”

Effect of Coulomb Interaction on Seebeck Coefficient of Organic Dirac Electron System $α$-(BEDT-TTF)$_2$I$_3$

“…Finally, the nearest-neighbor Coulomb interaction V a was used as a control parameter for the CO transition, rather than the actual pressure dependence, and we used transfer integrals at ambient pressure. The Seebeck coefficient was calculated using the Mott formula and ignoring electron-electron scattering, although the latter contributes to the behavior of the Seebeck coefficient [44] and the electron correlation effects play important roles in α-(BEDT-TTF) 2 I 3 [12,13,19,20,[28][29][30][31]. Phonon drag may also contribute to the peak structure near T = 0.005 of the Seebeck coefficient, although electronphonon scattering was ignored in this study.…”

“…The electron correlation effects play important roles in both phases. The CO phase is induced by nearestneighbor Coulomb interactions [12,13,17,18] and exhibits anomalous properties on the spin gap [19,20] and transport phenomena in α-(BEDT-TTF) 2 I 3 [21][22][23][24][25][26][27]. In the massless DE phase, the long-range Coulomb interaction suppresses the magnetic susceptibility, owing to Dirac cone reshaping and ferromagnetic polarization [28][29][30], and it enhances spin-triplet excitonic fluctuations, owing to perfect electron-hole nesting under an in-plane magnetic field [31].…”

Possible Spin-Density Wave on Fermi Arc of Edge State in Single-Component Molecular Conductors [Pt(dmdt)2] and [Ni(dmdt)2]

“…11,12 Strongly correlated Dirac electron systems in twodimensional organic conductors have been observed in α-(BEDT-TTF) 2 I 3 and similar substances via element substitution. [13][14][15][16][17][18][19] In fact, α-(BEDT-TTF) 2 I 3 exhibits a metal-insulator transition between the Dirac electron phase and the charge-ordered phase induced by nearestneighbor Coulomb interactions, [20][21][22] where anomalous spin-charge separation on spin gaps 23,24 and transport phenomena occur. [25][26][27] Furthermore, Coulomb interactions induce anomalous magnetic responses due to the reshaping of the Dirac cone, ferrimagnetism, and spin-triplet excitonic fluctuations in the Dirac electron phase.…”