Université de Fribourg

Strongly bound excitons in anatase TiO₂ single crystals and nanoparticles

Baldini, Eduardo ; Chiodo, Letizia ; Dominguez, A. ; Palummo, M. ; Moser, S. ; Yazdi-Rizi, Meghdad ; Auböck, G. ; Mallett, Benjamin P. P. ; Berger, Helmuth ; Magrez, Arnaud ; Bernhard, Christian ; Grioni, M. ; Rubio, Angel ; Chergui, Majed

In: Nature Communications, 2017, vol. 8, no. 1, p. 13

Anatase TiO₂ is among the most studied materials for light-energy conversion applications, but the nature of its fundamental charge excitations is still unknown. Yet it is crucial to establish whether light absorption creates uncorrelated electron–hole pairs or bound excitons and, in the latter case, to determine their character. Here, by combining steady-state angle-resolved...

Université de Neuchâtel

Remnant Fermi Surface in the Presence of an Underlying Instability in Layered 1T–TaS2

Pillo, Th. ; Hayoz, J. ; Berger, H. ; Grioni, M. ; Schlapbach, Louis ; Aebi, Philipp

In: Physical Review Letters, 1999, vol. 83, no. 17, p. 3494-3497

We report high resolution angle-scanned photoemission and Fermi surface (FS) mapping experiments on the layered transition-metal dichalcogenide 1T–TaS2 in the quasicommensurate (metallic) and the commensurate (insulating) charge-density-wave (CDW) phase. Instead of a nesting induced partially removed FS in the CDW phase we find a pseudogap over large portions of the FS. This...