Local spin susceptibility in the zero-gap-semiconductor state ofα−(BEDT-TTF)2I3probed by

Abstract

␣-͑BEDT-TTF͒ 2 I 3 has a double column structure with three crystallographically independent molecules, A, B, and C, and becomes an insulator below 135 K due to a charge-ordering ͑CO͒ transition. The CO state is suppressed under pressure and shows weak temperature dependence of the electrical resistance. The decline of the carrier density is observed over 1.8 GPa, suggesting a zero-gap-semiconductor state under high pressure. The local susceptibility on each site provides important information about the electronic band structure. In our previous work, molecular site B became spin poor and molecular site C became spin rich in the metallic state, suggesting the disproportionation of the local spin density. Therefore, it is worthwhile to investigate the behavior of the electron properties of each molecular site. We accessed the 13 C-NMR in this salt at ambient pressure and at 2.1 GPa. The analysis of the local spin susceptibility suggests that the disproportionation of the spin susceptibility at 2.1 GPa is enhanced from that at ambient pressure, and the spin susceptibility vanishes at low temperature at 2.1 GPa. Moreover, from the temperature dependence of T 1 −1 , we obtain the relation of.

Charge ordering and antiferromagnetism in (TMTTF)2SbF6

“…Recently, it was pointed out that the Knight shift had not only the contribution from on-site local spin susceptibility but also one from the neighboring molecules in the paramagnetic phase of α -(BEDT-TTF) 2 IBr 2 19 and there was the discrepancy between the disproportionation estimated by the Knight shift determined from the state at Fermi energy and one estimated by the chemical shift determined from all states below Fermi energy in the paramagnetic phase of α-(BEDT-TTF) 2 I 3 . 20 Therefore, to estimate the degree of charge disproportionation in the CO state, we should use the chemical shift. At the AF phase of (TMTTF) 2 SbF 6 , a axis, b axis, and c * axis were assigned as the spin hard axis, the easy axis, and the intermediate axis, respectively.…”

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

“…1(a)]. Sharp NMR spectra split by the dipolar interaction were observed above T CO ≈ 135 K, reflecting the four molecular sites in the unit cell [8,10]. The line positions exhibit large angular dependence on varying the field direction ψ [ Fig.…”

“…At ambient P, the Dirac cones are likely present at high T, since recent 13 C-NMR studies found, in the local spin density i, a large difference among nonequivalent sites i (= A, A', B, and C) -B < A (= A') < C -with strong T dependence. 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].…”

Microscopic modulation of local density of states in superconductingα−(BEDT-TTF)2NH4Hg(SCN)4studied by site-selectiveIhara1, Noda2, Kawamoto3 2014Phys. Rev. B

“…The local DOS at each molecular site can be estimated by applying the present analyses to the published data [25]. Even though the absolute values are different from those in NH 4 and Rb salts because of the difference in band structure, we can clearly conclude that the local DOS at the B site is much smaller than that at the A site, and comparable to the value for the C site, as shown in Fig.…”

“…In the Rb salt, 1/T 1 T decreases abruptly below 12 K due to the CDW transition, while NH 4 salt is in the Fermi liquid state down to the lowest temperature measured (4 K). The DOS at the Fermi surface vanishes in the CDW state, and becomes comparable to the [25]. The DOS at the B site is comparable to that at the C site.…”