66 research outputs found
Temperature dependence of the excitonic insulator phase model in 1T-TiSe2
Recently, detailed calculations of the excitonic insulator phase model
adapted to the case of 1\textit{T}-TiSe have been presented. Through the
spectral function theoretical photoemission intensity maps can be generated
which are in very good agreement with experiment [Phys. Rev. Lett. {\bf 99},
(2007) 146403]. In this model, excitons condensate in a BCS-like manner and
give rise to a charge density wave, characterized by an order parameter. Here,
we assume an analytical form of the order parameter, allowing to perform
temperature dependent calculations. The influence of this order parameter on
the electronic spectral function, to be observed in photoemission spectra, is
discussed. The resulting chemical potential shift and an estimation of the
resistivity are also shown.Comment: 4 pages, 3 figures, paper submitted at the Strongly Correlated
Electron System conference, Brazil, 200
Exciton Condensation Driving the Periodic Lattice Distortion of 1T-TiSeâ‚‚
We address the lattice deformation of 1T-TiSeâ‚‚ within the exciton condensate phase. We show that, at low temperature, condensed excitons influence the lattice through electron-phonon interaction. It is found that at zero temperature, in the exciton condensate phase of 1T-TiSeâ‚‚, this exciton condensate exerts a force on the lattice generating ionic displacements comparable in amplitude to what is measured in experiment. This is thus the first quantitative estimation of the amplitude of the periodic lattice distortion observed in 1T-TiSeâ‚‚ as a consequence of the exciton condensate phase
Exciton condensation driving the periodic lattice distortion of 1T-TiSe2
We address the lattice instability of 1T-TiSe2 in the framework of the
exciton condensate phase. We show that, at low temperature, condensed excitons
influence the lattice through electron-phonon interaction. It is found that at
zero temperature, in the exciton condensate phase of 1T-TiSe2, this exciton
condensate exerts a force on the lattice generating ionic displacements
comparable in amplitude to what is measured in experiment. This is thus the
first quantitative estimation of the amplitude of the periodic lattice
distortion observed in 1T-TiSe2 as a consequence of the exciton condensate
phase.Comment: 5 pages, 3 figures and 1 tabl
Spontaneous exciton condensation in 1T-TiSe2: a BCS-like approach
Recently strong evidence has been found in favor of a BCS-like condensation
of excitons in 1\textit{T}-TiSe. Theoretical photoemission intensity maps
have been generated by the spectral function calculated within the excitonic
condensate phase model and set against experimental angle-resolved
photoemission spectroscopy data. Here, the calculations in the framework of
this model are presented in detail. They represent an extension of the original
excitonic insulator phase model of J\'erome \textit{et al.} [Phys. Rev. {\bf
158}, 462 (1967)] to three dimensional and anisotropic band dispersions. A
detailed analysis of its properties and further comparison with experiment are
also discussedComment: Submitted to PRB, 11 pages, 7 figure
Temperature dependent photoemission on 1T-TiSe2: Interpretation within the exciton condensate phase model
The charge density wave phase transition of 1T-TiSe2 is studied by
angle-resolved photoemission over a wide temperature range. An important
chemical potential shift which strongly evolves with temperature is evidenced.
In the framework of the exciton condensate phase, the detailed temperature
dependence of the associated order parameter is extracted. Having a
mean-field-like behaviour at low temperature, it exhibits a non-zero value
above the transition, interpreted as the signature of strong excitonic
fluctuations, reminiscent of the pseudo-gap phase of high temperature
superconductors. Integrated intensity around the Fermi level is found to
display a trend similar to the measured resistivity and is discussed within the
model.Comment: 8 pages, 6 figure
Non-uniform doping across the Fermi surface of NbS2 intercalates
Abstract.: Magnetic ordering of the first row transition metal intercalates of NbS2 due to coupling between the conduction electrons and the intercalated ions has been explained in terms of Fermi surface nesting. We use angle-resolved photoelectron spectroscopy to investigate the Fermi surface topology and the valence band structure of the quasi-two-dimensional layer compounds Mn1/3NbS2 and Ni1/3NbS2. Charge transfer from the intercalant species to the host layer leads to non-uniform, pocket selective doping of the Fermi surface. The implication of our results on the nesting properties are discusse
Non-uniform doping across the Fermi surface of NbS intercalates
Magnetic ordering of the first row transition metal intercalates of NbS
due to coupling between the conduction electrons and the intercalated ions has
been explained in terms of Fermi surface nesting. We use angle-resolved
photoelectron spectroscopy to investigate the Fermi surface topology and the
valence band structure of the quasi-two-dimensional layer compounds
MnNbS and NiNbS. Charge transfer from the intercalant
species to the host layer leads to non-uniform, pocket selective doping of the
Fermi surface. The implication of our results on the nesting properties are
discussed
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