Regensburg 2004 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 30: Postersitzung IV: Kritische Ph
änomene, Quantenstörstellen, niederdimensionale Systeme

TT 30.8: Poster

Donnerstag, 11. März 2004, 14:30–19:00, Poster A

Mott Transition on the Surface of 1T-TaSe₂ studied by Angle-Resolved Photoemission — •Markus Hoinkis, Hidenori Fujiwara, Benjamin Schmid, Matthias Klemm, David Schrupp, Jörg Schäfer, Michael Sing, and Ralph Claessen — Institut für Physik, Universität Augsburg, 86135 Augsburg

The layered transition metal dichalcogenide 1T-TaSe₂ is known to be in a charge density wave phase below T₁=475K. Recently, an additional phase transition occurring only at the surface has been discovered at T₂=260K [1]. Below this temperature the density of states is strongly depressed at the Fermi energy. The authors of [1] have interpreted this as a bandwidth-controlled Mott transition: The temperature-dependent modulation of the atomic positions leads to a smaller bandwidth W of the Ta 5d-Band. While this modification of the ratio U/W (U is the on-site Coulomb interaction) does not suffice to trigger a Mott transition in the bulk, the effective bandwidth at the surface could be sufficiently small for this effect.

By angle-resolved photoemission we have studied the spectral evolution through the transition, with particular focus on the identification and dispersion of the quasiparticle and lower Hubbard band peaks.

[1] L. Perfetti et al., Phys. Rev. Lett. 90, 166401 (2003)