idw – Informationsdienst Wissenschaft
Nachrichten, Termine, Experten
Nachrichten, Termine, Experten
Abstract
Transition metal dichalcogenides (TMDC) form a class of low dimensional materials, the ground state of which is often unstable at low temperature towards the formation of a phase with a translational symmetry different than that of the high temperature phase, called a charge density wave (CDW) phase. Due to the electron-phonon coupling, this transition involves both the electronic and lattice degrees of freedom. Despite all the efforts invested for more than 30 years to understand the ground state of these materials, the mechanism at the origin of their CDW phase transition is not well understood so far. In this talk, I will present the particular case of the TMDC TiSe2 [1] and propose the spontaneous condensation of electron-hole pairs, called excitons, as the purely electronic driving force of its CDW transition. This exotic phase has been proposed theoretically a long time ago [2], but never unambiguously observed. For TiSe2, this scenario is supported by the good agreement between measured angle-resolved photoemission spectroscopy data and photoemission intensity maps calculated by the spectral function within this model [3]. Furthermore, from theoretical considerations, I will show that condensed excitons are capable of producing the observed periodic lattice distortion through the electron-phonon coupling [4] and that electron-hole fluctuations are preparing the transition [5].
References:
[1] F. J. Di Salvo et al., Phys. Rev. B 14, 4321 (1976).
[2] D. Jérôme et al., Phys. Rev., 158 462 (1967).
[3] H. Cercellier et al., Phys. Rev. Lett. 99, 146403 (2007).
[4] C. Monney et al., Phys. Rev. Lett. 106, 106404 (2011).
[5] C. Monney et al., New J. Phys. 14, 075026 (2012).
Information on participating / attending:
Organisation: Prof. H. Fehske und Prof. L. Schweikhard
Ansprechpartner: Institut für Physik, Felix-Hausdorff-Straße 6, 17487 Greifswald,
Telefon 03834 86-4700, info@physik.uni-greifswald.de
Date:
05/16/2013 17:00 - 05/16/2013 18:00
Event venue:
Großer Hörsaal der Physik
Felix-Hausdorff-Straße 6
17489 Greifswald
Mecklenburg-Vorpommern
Germany
Target group:
Scientists and scholars, Students
Relevance:
transregional, national
Subject areas:
Physics / astronomy
Types of events:
Presentation / colloquium / lecture
Entry:
01/28/2013
Sender/author:
Sabine Köditz
Department:
Presse- und Informationsstelle
Event is free:
no
Language of the text:
German
URL of this event: http://idw-online.de/en/event42389
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