pres splds 2012
TRANSCRIPT
Electron – holeinstabilities in TiSe2
Gaël MonneyUniversity of Fribourg, Switzerland
Our group & collaborators
Electron spectroscopy group in Fribourg• Clément Didiot, Zuzana Vydrova,
Nicolas Mariotti (Gunnar Garnier, Eike Schwier)
• Philipp Aebi Collaborations• Hans Beck, Univ. of Neuchâtel• Claude Monney, PSI, Switzerland• H. Berger, EPFL
1
Part 1 :
The context
Charge density waves (CDW) Peierls transitions (electron signature)
2
Charge density waves (CDW) Kohn anomaly (phonon signature)
3
CDW : driving forces Fermi Surface Nesting
Jahn-Teller effect
Excitons
4
TiSe2 properties
Reciprocal space
Real space
TiSe
Di S
alvo
et a
l., P
RB,
1976
5
Part 2 :
Experiments
Electronic signatures (by ARPES)
6
Other measurements 7
Part 3 :
The models
Exciton BCS model ( )
Hamiltonian
Green’s functions
Anomalous Green’s functions
Order parameter
8
Exciton BCS model ( )
9
Previous model : Hervé Cercellier et al., PRL, 2007
Electron – hole fluctuations ( ) The model
Definitions
Electron-hole susceptibility
Bethe-Salpeter equation
10
Electron – hole fluctuations The physics
11
Part 4 :
The results
Crossings vs. nesting 12
Electron renormalization Comparison
13
Phonon renormalization 14
Part 5 :
Outlook
Chirality 15
Thanks
Part I : CDWs
Part 2 : Experiments
Part 3 : Models
Part 4 : Results