Semimetallic character of TiSe2and semiconductor character of TiS2under pressure

Abstract

Presents room-temperature measurements of the in-plane resistivity (j,E_{perpendicular to} c) and Hall coefficient (j_{perpendicular to c},B/sub //c/) of TiSe₂ and TiS₂ as a function of pressure. With pressure both the resistivity and Hall coefficient decrease rapidly in TiSe₂; this the authors interpret in terms of a changing p-d band overlap, and is consistent with the semimetallic picture for this material. In contrast, the Hall coefficient of TiS₂ is completely independent of pressure, indicating that the carriers present do not arise from this p-d band overlap, but rather from partial occupation of the band as a result of slight Ti excess. Thus the extrinsic semiconductor picture for TiS₂ is favoured by the authors.