A Monomer Mott Insulator (BEDT-TTF)Cu[N(CN)$_2$]$_2$ as a Potential Nodal Line System

TL;DR

This paper combines theoretical band structure calculations and experimental measurements to explore the electronic properties of a monomer Mott insulator, revealing potential nodal line features and a spin-singlet ground state.

Contribution

It provides the first combined theoretical and experimental analysis of BEDT-TTF Cu[N(CN)$_2$]$_2$, highlighting strong electron correlation effects and the emergence of a spin-singlet ground state.

Findings

Band calculations suggest a Dirac semimetal state with nodal lines.

Resistivity and susceptibility data support a monomer Mott insulating state.

Observation of a spin-singlet ground state below 25 K.

Abstract

We report the band structure calculations and the experimental results of resistivity and magnetic susceptibility in a spin-1/2 (BEDT-TTF)$^{\bullet +}$ monomer Mott insulator (BEDT-TTF)Cu[N(CN)$_2$]$_2$. The band calculations indicate a Dirac semimetal state with nodal lines at the Fermi level. The resistivity and the magnetic susceptibility as functions of temperature are well interpreted in terms of the monomer Mott insulating state instead of the expected semimetal state probably owing to strong electron correlation. In addition, we find that an Arrhenius-type steep reduction of the paramagnetic susceptibility appears below approximately 25 K, which indicates a spin-singlet ground state.