Dramatic effective mass reduction driven by a strong potential of competing periodicity

¹ Département de Physique and Fribourg Center for Nanomaterials, Université de Fribourg CH-1700 Fribourg, Switzerland
² Research Department Synchrotron Radiation and Nanotechnology, Paul Scherrer Institut CH-5232 Villigen PSI, Switzerland
³ EPFL, Institute of Microengineering, Photovoltaics and Thin Film Electronics Laboratory CH-2000 Neuchâtel, Switzerland
⁴ Institut Néel, CNRS-UJF - BP 166, 38042 Grenoble, France, EU
⁵ EPFL, Institut de Physique de la Matière Condensée - CH-1015 Lausanne, Switzerland
⁶ Institute of Metal Physics UrD RAS - Ekaterinburg, 620219, Russia
⁷ Institute of Metallurgy UrD RAS - Amundsen St. 101, Ekaterinburg, 620016, Russia

^a philipp.aebi@unifr.ch

Received: 13 July 2010
Accepted: 27 October 2010

Abstract

We present angle-resolved photoemission experiments on 1T-TiSe₂ at temperatures ranging from 13 K to 288 K. The data evidence a dramatic renormalization of the conduction band below 100 K, whose origin can be related to the new potential responsible for the charge density wave phase at low temperature in this system. The renormalization translates into a substantial effective mass reduction of the dominant charge carriers and this observation is thus in opposition to the common belief that strong interactions produce heavier quasiparticles through an increased effective mass.