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 R xy is almost constant and R xx 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) 2 X 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.