Comparison of the Fermi-surface topologies of kappa-(BEDT-TTF)_2 Cu(NCS)_2 and its deuterated analogue

TL;DR

This study compares the Fermi-surface topologies of kappa-(BEDT-TTF)_2 Cu(NCS)_2 and its deuterated form, revealing significant differences that influence superconductivity and support electron-electron interaction models.

Contribution

It provides detailed measurements of Fermi-surface differences between the two compounds, linking these to the inverse isotope effect in superconductivity.

Findings

Deuteration alters Fermi-surface corrugations.

Differences in Fermi-surface topology relate to changes in superconducting transition temperature.

Results support models emphasizing electron-electron interactions based on Fermi surface topology.

Abstract

We have measured details of the quasi one-dimensional Fermi-surface sections in the organic superconductor kappa-(BEDT-TTF)_2 Cu(NCS)_2 and its deuterated analogue using angle-dependent millimetre-wave techniques. There are significant differences in the corrugations of the Fermi surfaces in the deuterated and undeuterated salts. We suggest that this is important in understanding the inverse isotope effect, where the superconducting transition temperature rises on deuteration. The data support models for superconductivity which invoke electron-electron interactions depending on the topological properties of the Fermi surface.