We present angle-resolved photoemission experiments on 1T-TiSe2 at temperatures ranging from 13K to 288K. The data evidence a dramatic renormalization of the conduction band below 100K, whose origin can be explained with the exciton condensate phase model. The renormalization translates into a substantial effective mass reduction of the dominant charge carriers and can be directly related to the low temperature downturn of the resistivity of 1T-TiSe2. This observation is in opposition to the common belief that strong interactions produce heavier quasiparticles through an increased effective mass.
@article{arxiv.0912.5283,
title = {Dramatic effective mass reduction driven by strong electronic correlations},
author = {C. Monney and E. F. Schwier and M. G. Garnier and C. Battaglia and N. Mariotti and C. Didiot and H. Cercellier and J. Marcus and H. Berger and A. N. Titov and H. Beck and P. Aebi},
journal= {arXiv preprint arXiv:0912.5283},
year = {2009}
}