Magnetic-Field-Induced Phase Transition and a Possible Quantum Hall Effect in the Quasi-One-Dimensional CDW Organic Conductor HMTSF-TCNQ

Abstract

In the Temperature-Pressure phase diagram, the quasi-one-dimensional conductor, HMTSF-TCNQ, the ground state at ambient pressure is an insulator of charge density wave (CDW) below 30 K, while it shows a good metallic nature at higher temperature. The CDW insulating state is suppressed by a pressure of 1 GPa, which is considered to be a quantum critical point. Neither at 0 -0.5 nor 2 GPa but only around this critical point in pressure, field-induced phases appear from 0.2 T through 10 T, where Rxy is almost constant and Rxx is very low. These phenomena are achieved when the magnetic field is applied along the least conducting axis. The behaviors are consistent with a kind of Quantum Hall Effect (QHE). The field-induce phase accompanied by the QHE might be the field-induced CDW (FICDW) similar to that of FISDW, observed in (TMTSF)2X salts. This paper presents the latest result of the Hall effects reviewing the history of the authors' work on this material from preliminary to the latest ones.

Quasi one-dimensional organic conductors: from Fröhlich conductivity and Peierls insulating state to magnetically-mediated superconductivity, a retrospective

“…In addition, the possibility of a field-induced charge density wave state (topic not covered in the present article, see Ref. [169] for instance), have been claimed when the component of the magnetic field along the least conducting direction exceeds 10T (under 1.1 GPa) accompanied by the observation of a quantized Hall effect and angular magnetoresistance oscillations [168,170]. These remain interesting possibilities which will require further confirmations.…”

Possible quantum Hall effect in a magnetic-field-induced phase transition in the quasi-one-dimensional CDW organic conductor, HMTSF–TCNQ

“…Below 0.2 T, R xy is negative and proportional to B z . The fact that R xy is proportional to B z shows that a field-induced state is not present at least below 0.2 T. These data are published elsewhere [7].…”

“…Such crystals had broad Bragg spots, and the signature of the CDW transition in the resistivity was neither sharp nor large. More recently, one (R.K.) of the authors succeeded in synthesizing high-quality single crystals; and our understanding of the field-induced phase has drastically advanced or even renewed as a result [7]. This paper presents the state of art on the magnetic-field-induced phase in HMTSF-TCNQ using the most refined samples.…”

“…To examine precisely the possible FICDW and quantum Hall effect, we studied magneto-resistance, angular dependence of mangetoresistance oscillations (AMRO) and Hall effect [6,7].…”

History of crystalline organic conductor

“…Below 0.37 and above 1.67 GPa, such phenomena were not observed. 31) 4. α-(BEDT-TTF) 2 I 3 and β-(BEDT-TTF) 2 I 3 Back to the history of organic conductors, the second generation of organic superconductors, β-(BEDT-TTF) 2 I 3 appeared in 1984 after the first discovery of superconductivity in (TMTSF) 2 PF 6 in 1980. Since β-(BEDT-TTF) 2 I 3 showed surprisingly a high T c of 8 K, [3][4][5] this material attracted attention.…”