# A spin-gapped Mott insulator with the dimeric arrangement of twisted molecules Zn(tmdt)$_{2}$

## TL;DR

This study uses $^{13}$C NMR to reveal that Zn(tmdt)$_{2}$ is a spin-gapped Mott insulator with strong electron correlations, featuring a dimeric molecular arrangement similar to known quasi-two-dimensional systems.

## Contribution

First detailed $^{13}$C NMR analysis of Zn(tmdt)$_{2}$ showing its spin gap and strong correlations in a dimeric molecular structure.

## Key findings

- Identified spin gap through NMR measurements.
- Observed singlet-triplet excitations of $\
- Confirmed strong electron correlations in Zn(tmdt)$_{2}$.

## Abstract

$^{13}$C nuclear magnetic resonance measurements were performed for a single-component molecular material Zn(tmdt)$_{2}$, in which tmdt's form an arrangement similar to the so-called ${\kappa}$-type molecular packing in quasi-two-dimensional Mott insulators and superconductors. Detailed analysis of the powder spectra uncovered local spin susceptibility in the tmdt ${\pi}$ orbitals. The obtained shift and relaxation rate revealed the singlet-triplet excitations of the ${\pi}$ spins, indicating that Zn(tmdt)$_{2}$ is a spin-gapped Mott insulator with exceptionally large electron correlations compared to conventional molecular Mott systems.