Mott Transition from a Spin Liquid to a Fermi Liquid in the Spin-Frustrated Organic Conductor kappa-(ET)2Cu2(CN)3

TL;DR

This study investigates the pressure-induced Mott transition in the spin-liquid organic conductor ppa-(ET)2Cu2(CN)3, revealing a transition from a spin-liquid to a Fermi-liquid state influenced by spin frustration.

Contribution

It provides experimental evidence of a Mott transition from a spin liquid to a Fermi liquid in a triangular lattice organic conductor, emphasizing the role of spin frustration.

Findings

Persistence of the spin-liquid phase before the Mott transition.

Rapid suppression of spin fluctuations at the transition.

Observation of Fermi-liquid behavior post-transition.

Abstract

Pressure-temperature phase diagram of the organic Mott insulator $\kappa$-(ET)$_2$Cu$_2$(CN)$_3$, a model system of the spin liquid on triangular lattice, has been investigated by $^1$H NMR and resistivity measurements. The spin-liquid phase is persistent before the Mott transition to the metal or superconducting phase under pressure. At the Mott transition, the spin fluctuations are rapidly suppressed and the Fermi-liquid features are observed in the temperature dependence of the spin-lattice relaxation rate and resistivity. The characteristic curvature of Mott boundary in the phase diagram highlights a crucial effect of the spin frustration on the Mott transition.