Comparative magnetotransport andT_cmeasurements on  -(BEDT-TTF)₂Cu(SCN)₂under pressure

Abstract

Abstract.We compare magnetotransport measurements under pressure on the organic superconductor κ-(BEDT-TTF) 2 Cu(SCN) 2 with different pressure-media and discover that the results are pressure media dependent. This pressure-medium dependence is thought to originate from the difference in thermal contraction between the very soft and highly anisotropic sample and the isotropically contracting, but solid pressure medium, thus resulting in non-hydrostatic pressure on the sample. However, comparison of pressure measurements with different media reveals a pressure-medium independent correlation between the superconducting transition temperature, Tc, and the size of the quasi 2-dimensional Fermi surface pocket and thus the quasi 2-dimensional carrier density in κ-(BEDT-TTF) 2 Cu(SCN) 2 . The observed pressure-induced increase in the quasi 2-dimensional carrier density can be interpreted as a transfer of carriers from quasi 1-dimensional Fermi surface sections, reminiscent of a mechanism in cuprate superconductors, where pressure is known to transfer carriers from the insulating charge reservoir layers into the conducting cuprate sheets.

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“…The measurements compared in this paper have been published previously [15,[18][19][20] and details about the measurement techniques can be found in those publications; details of the measurements on κ-(h 8 -BEDT-TTF) 2 Cu(SCN) 2 with petroleum spirit as a pressure medium can be found in [18]. The corresponding measurements on κ-(d 8 -BEDT-TTF) 2 Cu(SCN) 2 with helium and Fluorinert are described in detail in [20] and [15], respectively.…”

“…The corresponding measurements on κ-(d 8 -BEDT-TTF) 2 Cu(SCN) 2 with helium and Fluorinert are described in detail in [20] and [15], respectively. The ac susceptibility measurements are published in [19].…”

“…The ac susceptibility measurements are published in [19]. The sample of κ-(d 8 -BEDT-TTF) 2 Cu(SCN) 2 investigated in the magnetotransport measurements in [20] is from the same batch as that investigated in [19].…”

“…Several magnetotransport measurements under pressure using different pressure media [18,15,20] were performed on single crystals of κ-(BEDT-TTF) 2 Cu(SCN) 2 with different isotope compositions [20] and from different growers [15]. It is known, that neither the crystal grower [15] nor the isotope composition [19] has an effect on the pressure dependence of κ-(BEDT-TTF) 2 Cu(SCN) 2 .…”

“…It is known, that neither the crystal grower [15] nor the isotope composition [19] has an effect on the pressure dependence of κ-(BEDT-TTF) 2 Cu(SCN) 2 . Figures 5 (a) and (b) [20] compare measurements with three different pressure media: helium, Fluorinert and petroleum spirit.…”