Shear-induced superconductivity inβ-di[-Bis(ethylene- dithio)tetrathiafulvalene]triiodide[β-(BEDT-TTF)2I3]

Abstract

We show that the high-$T_c$ (8-K) superconducting state of β-(BEDT-TTF${)}_2$ ${\mathrm{I}}_3$ [β-(${\mathrm{C}}_{10}$ ${\mathrm{H}}_8$ ${\mathrm{S}}_8$ ${)}_2$ ${\mathrm{I}}_3$] is formed by a combination of shear stress and hydrostatic presure and cannot be accessed by presence alone. Also, measurements of the pressure dependence of $T_c$ in the ambient-pressure superconductors β-(BEDT-TTF${)}_2$ ${\mathrm{I}}_3$, β-(BEDT-TTF${)}_2$ ${\mathrm{IBr}}_2$, and β-(BEDT-TTF${)}_2$ ${\mathrm{AuI}}_2$ show a common pressure derivative of about 1 K/kbar, which is nearly an order of magnitude larger than that of any previously reported superconductor. We present a structural model which is consistent with these observations.