Kikuchi Koichi

High Field Magnetoconductivity in (TMTSF)2ClO4

High field magnetoresistivity in (TMTSF) 2 ClO 4 was measured down to 0.52 K and up to 13 T. Magnetoconductivity tensor components are derived assuming two-dimensional anisotropy. It is confirmed that some part of previously reported oscillations which have been attributed to the Shubnikov-de Haas effect should be regarded as discontinuous changes of magnetoresistance caused by the stepwise decrease in the effective carrier density due to successive phase transitions. This conclusion is supported by the field dependence of the longitudinal magnetoresistivity component ( ρ zz ). The sign of the Hall coefficient is negative at high field.

Uniaxial-Strain-Orientation Dependence of the Competition between Mott and Charge Ordered Phases and their Corresponding Superconductivity of β-(BDA-TTP)2I3

We studied the electronic transport properties of the charge transfer salt β-(BDA-TTP) 2 I 3 [BDA-TTP: 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene] by applying uniaxial strains along the three crystallographic axes, and obtained three corresponding temperature-pressure phase diagrams. Three phase diagrams were quite dependent on the direction of compression. Following the preceding paper by Kikuchi et al. , we speculate that the insulating states are of 1/2-filled Mott insulators for the a - and b -axes compressions, and of 1/4-filled charge ordered states for the c -axis compression as well as hydrostatic pressure. The superconducting phase under uniaxial strain was realized with T c = 5 K at 1.9 GPa along the a -axis and with T c = 5.6 K at 1.75 GPa along the b -axis. Superconductivity was also reproduced with a T c of 9.5 K at 1.0 GPa for the c -axis compressions in the range of 0.85 to 1.53 GPa as previously reported. We studied tentative measurement on upper critical fields, B c2 s of ...