Relation between Thermally Induced Structural Distortions and Electronic Properties of the Layered Misfit Chalcogenide (LaS)1.196VS2

Abstract

Interplay between electronic and structural properties of the misfit layered chalcogenide (LaS)1.196VS2 crystals was investigated by transport, optical measurements, angle-resolved photoemission (ARPES), Raman spectroscopy, and X-ray diffraction. Although no clear anomaly is found in temperature-dependent transport measurements, a large spectral weight transfer, around 1 eV, is observed by both optical and photoemission spectroscopies. ARPES reveals a nearly filled band with negative curvature, close enough from the Fermi level at room temperature to produce metallic-like behavior as observed in optical conductivity spectra. At low temperature, the band structure is strongly modified, yielding to an insulating state with an optical gap of 120 meV. Both Raman spectroscopy and accurate (3 + 1)D analysis of X-ray diffraction data show that, although a phase transition does not occur, structural distortions increase as temperature is decreased, and vanadium clusterization is enhanced. We found that the change...