Possible observation of the signature of the bad metal phase and its crossover to a Fermi liquid in K(BEDT-TTF)2Cu(NCS)2 bulk and nanoparticles by Raman scattering

TL;DR

This study uses Raman scattering to identify signatures of the bad metal phase and its crossover to a Fermi liquid in K(BEDT-TTF)2Cu(NCS)2, revealing temperature-dependent phonon behavior in bulk and nanoparticles.

Contribution

First observation of phonon signatures indicating the bad metal phase and its crossover to a Fermi liquid in this compound using Raman spectroscopy.

Findings

Plateau in phonon frequencies between 50 and 100 K in bulk

Anomalies at 50 K in nanoparticles indicating phase crossover

Assignment of phonon modes from 20 to 1600 cm-1

Abstract

K(BEDT-TTF)2Cu(NCS)2 has been investigated by Raman scattering in both bulk and nanoparticle compounds. Phonon modes from 20 to 1600 cm-1 have been assigned. Focusing on the unexplored low frequency phonons, a plateau in frequencies is observed in the bulk phonons between 50 and 100 K and assigned to the signature of the bad metal phase. Nanoparticles of K(BEDT-TTF)2Cu(NCS)2 exhibit anomalies at 50 K associated to the crossover from a bad metal to a Fermi liquid whose origins are discussed.