Pressure-induced topological changes in Fermi surface of two-dimensional molecular conductor

Abstract

We demonstrated X-ray structural analysis of the pressure-induced superconductor, $β'$-ET${}_2$ICl${}_2$ under extremely high-pressure conditions, where ET denotes bis(ethylenedithio)tetrathiafulvalene. This material has been known as the highest transition temperature ($T_c$) superconductor among organic superconductors ($T_c=14.2$ K at $8.2$ GPa). On the basis of the experimental results, ab-initio models were derived using the constrained random phase approximation. We revealed that the Lifshitz transition exists behind the Mott insulator-metal transition and found that the value of the on-site Coulomb interaction was halved to around $10$ GPa compared to that at ambient pressure. This study clarifies the enigmatic origins of high $T_{\mathrm{c}}$, and concurrently, provides a new understanding of the impacts of structural alterations in organic materials under high pressure on their electronic properties and the superconductivity process.

8 pages, 4 figures; Supplemental Material: 9 pages, 6 figures, accepted for publication in Phys. Rev. Materials (Letter)