Cascade of Field-Induced Phase Transitions in the Organic Metal Tetramethyltetraselenafulvalenium Perchlorate [(TMTSF)2ClO4]

Abstract

We present specific-heat measurements as a function of field (3-6 T) and temperature (0.35-1.7 K) of a single crystal of the organic conductor tetramethyltetraselenafulvalenium perchlorate [${\mathrm{}\left(\mathrm{TMTSF}\right)\mathrm{}}_2$Cl${\mathrm{O}}_4$]. The small electronic contribution, 40 nJ/K, shows clearly above a temperature-dependent threshold field, a series of jumps and peaks. The phase diagram deduced from this magnetocalorimetric investigation exhibits in the threshold region indications of a partial reentrance of the normal metal in between semimetallic regions.