Pressure dependence of the resistivity of (BEDO-TTF)2ReO4·(H2O)

Abstract

The temperature dependence of the resistivity under pressure (up to 6kbar) of the organic metal (BEDO-TTF)2ReO4(H20) was investigated. The increase of the resistivity below 35K, which is observed at ambient pressure, is already totally suppressed at I kbsr. In addition at this pressure the superconducting transition sharpens drastically and the onset temperature of 2.3 K is nearly the same as at ambient pressure.

Characterisation of the Fermi surface and phase transitions of (BEDO-TTF)2 ReO4�(H2O) by physical property measurements and electronic band structure calculations

“…(H20 ) the resistivity ratio pc:pa,:pb,.~ 1:3:1000 [10,11]. This indicates that the electronic properties of the (BEDO-TTF)zReO4.…”

“…This explains the presence of the closed Fermi surface pockets at temperatures below 5 K as observed by the SdH oscillations. In addition, this also explains the fact that a relatively low isotropic pressure of less than 1 kbar is sufficient to suppress the resistivity increase below 35 K [9][10][11] and sharpen the superconducting transition [-101. In the case of (BEDO-TTF)2ReO4.…”

“…The dc resistivity [8,9] and thermopower [8] of (BEDO-TTF)zReO4. (H20) exhibit a metallic behavior down to 213 K, where a first order phase transition occurs [8][9][10] and the resistivity abruptly decreases by about a factor of two. In the temperature range between 213 K and about 35 K, the crystal again exhibits a metallic character, from --~ 35 K to 4 K, the resistivity increases considerably and finally starts to decrease below ~ 3 K to reach a superconducting state with an onset temperature of 2.4 K. In addition, thermopower measurements [8] suggest another phase transition at ~ 90 K but also show a clear metallic behavior for the temperature range below 35 K. The occurrence of several phase transitions is interesting especially because (BEDO-TTF)zReO4.…”

“…In the temperature range between 213 K and about 35 K, the crystal again exhibits a metallic character, from --~ 35 K to 4 K, the resistivity increases considerably and finally starts to decrease below ~ 3 K to reach a superconducting state with an onset temperature of 2.4 K. In addition, thermopower measurements [8] suggest another phase transition at ~ 90 K but also show a clear metallic behavior for the temperature range below 35 K. The occurrence of several phase transitions is interesting especially because (BEDO-TTF)zReO4. (H20) is a two dimensional (2D) metal according to the dc resistivity measurements [10] and preliminary measurements of Shubnikov de Haas (SdH) oscillations in magnetic fields below 7 T…”

“…The metal metal transition at 213 K can be suppressed by a pressure of about 19 kbar [9][10][11]. On the other hand, a relatively small pressure of 1 kbar is already sufficient to suppress the increase in resistivity below 35 K and sharpen the superconducting transition [10,11].…”