Effect of the dimerized gap due to anion ordering in the field-induced spin-density-wave of quasi-one dimensional organic conductors

Nonperturbative effects of the periodic potential on the field-induced spin-density wave and the sign of the quantum Hall effect in the quasi-one-dimensional conductor(TMTSF)2ClO4

“…7-9. In the 1/V and B phase diagram of the nonperturbation, the negative ͑N =−2͒ phase appears when 1/͑V / t b ͒ Շ 30, whose features qualitatively agree with the recent experimental results by Matsunaga et al 51 Zanchi and Montambaux 28 have shown that the higher harmonics ͑t 3 and t 4 ͒ are necessary for the existence of the negative N phase in the absence of anion ordering. In order to see whether t 3 and t 4 are necessary for the negative N phase in the presence of anion ordering, the local maximum values of 0 ͑q͒ at t 3 = t 4 = 0 and V / t b = 0.1 in nonperturbation are shown in Fig.…”

“…We have calculated the local peaks of the susceptibility as a function of the magnetic field B for various values of V and obtained the 1 / V and B phase diagram. We have shown that in ClO 4 the negative phase ͑N =−2͒ exists for large values of V ͑V / t b տ 0.03͒, even for small values of the higher-order hoppings, t 3 and t 4 , where there exists only positive N in the absence of V. The obtained phase diagram is in good agreement with that reported recently by Matsunaga et al 51 For the large value of V, the peaks of 0 ͑q͒ of odd N oscillate as a function of B in the opposite phase to the peaks of even N. Thus the FISDW with N = −2, which is suppressed by V in general, is stabilized in some region in the 1 / V and B phase diagram, because the FISDWs with odd N are much suppressed in these regions of parameters. …”

“…Moreover, Matsunaga et al 51 observed R xy and R zz in various cooling rates from 0.000 09 K / s ͑very slow cooling͒ to 0.33 K / s ͑rapid cooling͒ at T Ӎ 0.45 and 1.3 K. They found that a negative Hall plateau of R xy appears when the cooling rate is below ϳ0.03 K / s. In this paper, in order to study the relation between the cooling rate and FISDW of ͑TMTSF͒ 2 ClO 4 , we focus on the nonperturbative effect of V and the higher harmonics ͑t 3 and t 4 ͒ of the tight-binding model, because the nonperturbative calculation [40][41][42][43][44][45][46]48,49 is necessary for large V, and t 3 and t 4 are thought to be the origin 28 of the negative plateau of R xy . The parameter V / t b is changed from 0 to 0.2.…”

Role of the Anion Ordering in the Field Induced SDW Phase

“…In the case of the ClO 4 salt, there is no such a wide negative Hall phases under low magnetic field. This difference between the ReO 4 salt and the ClO 4 salt is caused by the dynamic changing of the nesting vector in the ClO 4 salt from the conventional QNM [11] [14] [15]. In conclusion, we have measured the Hall resistance in the FISDW phase of (TMTSF) 2 ReO 4 for various pressure down to 0.24K.…”

Negative quantum Hall effect in field-induced spin-density-wave states: Dependence on shape of the quasi-one-dimensional Fermi surface

“…38 The shape of the Fermi surface is also affected by the anion ordering at T AO =24 K in ͑TMTSF͒ 2 ClO 4 . Interesting properties have been reported in the magnetic field, i.e., the superconducting critical temperature with the anomalous inplane anisotropy, 39,40 which is attributed to the Fulde-Ferrel-Larkin-Ovchinnikov ͑FFLO͒ state, 41,42 the unclosed anomalous FISDW first-order transition line in the B-temperature ͑T͒ phase diagram, [43][44][45] the periodic oscillation 46 with sign reversal of R xy above B Ӎ 26 T, etc. The alternating ordering of the anion ClO 4 in the y direction below T AO =24 K is thought to cause these phenomena.…”