390 research outputs found
Spectral sum rules for the Tomonaga-Luttinger model
In connection with recent publications we discuss spectral sum rules for the
Tomonaga-Luttinger model without using the explicit result for the one-electron
Green's function. They are usefull in the interpretation of recent high
resolution photoemission spectra of quasi-one-dimensional conductors. It is
shown that the limit of infinite frequency and band cut\-off do not commute.
Our result for arbitrary shape of the interaction potential generalizes an
earlier discussion by Suzumura. A general analytical expression for the
spectral function for wave vectors far from the Fermi wave vector is
presented. Numerical spectra are shown to illustrate the sum rules.Comment: 9 pages, REVTEX 3.0, 2 figures added as postscript file
How universal is the one-particle Green's function of a Luttinger liquid?
The one-particle Green's function of the Tomonaga-Luttinger model for
one-dimensional interacting Fermions is discussed. Far away from the origin of
the plane of space-time coordinates the function falls off like a power law.
The exponent depends on the direction within the plane. For a certain form of
the interaction potential or within an approximated cut-off procedure the
different exponents only depend on the strength of the interaction at zero
momentum and can be expressed in terms of the Luttinger liquid parameters
and of the model at hand. For a more general
interaction and directions which are determined by the charge velocity
and spin velocity the exponents also depend on the
smoothness of the interaction at zero momentum and the asymptotic behavior of
the Green's function is not given by the Luttinger liquid parameters alone.
This shows that the physics of large space-time distances in Luttinger liquids
is less universal than is widely believed.Comment: 5 pages with 2 figure
Boundary Effects on Spectral Properties of Interacting Electrons in One Dimension
The single electron Green's function of the one-dimensional
Tomonaga-Luttinger model in the presence of open boundaries is calculated with
bosonization methods. We show that the critical exponents of the local spectral
density and of the momentum distribution change in the presence of a boundary.
The well understood universal bulk behavior always crosses over to a boundary
dominated regime for small energies or small momenta. We show this crossover
explicitly for the large-U Hubbard model in the low-temperature limit.
Consequences for photoemission experiments are discussed.Comment: revised and reformatted paper to appear in Phys. Rev. Lett. (Feb.
1996). 5 pages (revtex) and 3 embedded figures (macro included). A complete
postscript file is available from http://FY.CHALMERS.SE/~eggert/luttinger.ps
or by request from [email protected]
Interpretation of Photoemission Spectra of (TaSe4)2I as Evidence of Charge Density Wave Fluctuations
The competition between different and unusual effects in
quasi-one-dimensional conductors makes the direct interpretation of
experimental measurements of these materials both difficult and interesting. We
consider evidence for the existence of large charge-density-wave fluctuations
in the conducting phase of the Peierls insulator (TaSe4)2I, by comparing the
predictions of a simple Lee, Rice and Anderson theory for such a system with
recent angle-resolved photoemission spectra. The agreement obtained suggests
that many of the unusual features of these spectra may be explained in this
way. This view of the system is contrasted with the behaviour expected of a
Luttinger liquid.Comment: Archive copy of published paper. 19 pages, 12 figures, uses IOP
macro
Anderson impurity in pseudo-gap Fermi systems
We use the numerical renormalization group method to study an Anderson
impurity in a conduction band with the density of states varying as rho(omega)
\propto |omega|^r with r>0. We find two different fixed points: a local-moment
fixed point with the impurity effectively decoupled from the band and a
strong-coupling fixed point with a partially screened impurity spin. The
specific heat and the spin-susceptibility show powerlaw behaviour with
different exponents in strong-coupling and local-moment regime. We also
calculate the impurity spectral function which diverges (vanishes) with
|omega|^{-r} (|\omega|^r) in the strong-coupling (local moment) regime.Comment: 8 pages, LaTeX, 4 figures includes as eps-file
Phase diagram of the one-dimensional extended Hubbard model with attractive and/or repulsive interactions at quarter filling
We study the phase diagram of the one dimensional (1D) model at quarter
filling in the most general case where the on-site and first-neighbour
interactions and can be both attractive and repulsive. The results have
been obtained using exact diagonalization of small clusters and variational
techniques, as well as exact results in various limits. We have analyzed four
properties of the groundstate: i)~whether it is insulating or metallic;
\hbox{ii)~whether} it is homogenous or phase separated; iii)~whether it has a
spin gap; iv)~whether it has dominant superconducting fluctuations. With eight
phases, the resulting phase diagram is unexpectedly rich. The four phases not
found in the weak coupling limit are: i) an insulating phase when and
are large enough; ii) a region of phase separation when is attractive; iii)
another region of phase separation when is large enough and small; iv)
a region with dominant superconducting fluctuations when is intermediate
and small. The actual nature of this last phase, which has pairs but no
spin gap, is not fully clear yet.Comment: 24 pages, RevTeX (4 postscript figures attached to the end
Remnant Fermi surface in the presence of an underlying instability in layered 1T-TaS_2
We report high resolution angle-scanned photoemission and Fermi surface (FS)
mapping experiments on the layered transition-metal dichalcogenide 1T-TaS_2 in
the quasi commensurate (QC) and the commensurate (C) 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 remnant FS exhibits the
symmetry of the one-particle normal state FS even when passing from the
QC-phase to the C-phase. Possibly, this Mott localization induced transition
represents the underlying instability responsible for the pseudogapped FS
Spectral function of the 1D Hubbard model in the limit
We show that the one-particle spectral functions of the one-dimensional
Hubbard model diverge at the Fermi energy like
in the limit. The Luttinger liquid behaviour
, where as ,
should be limited to (for large but
finite), which shrinks to a single point, ,in that limit.
The consequences for the observation of the Luttinger liquid behaviour in
photoemission and inverse photoemission experiments are discussed.Comment: 4 pages, RevTeX, 2 figures on reques
Crossover from Luttinger- to Fermi-liquid behavior in strongly anisotropic systems in large dimensions
We consider the low-energy region of an array of Luttinger liquids coupled by
a weak interchain hopping. The leading logarithmic divergences can be re-summed
to all orders within a self-consistent perturbative expansion in the hopping,
in the large-dimension limit. The anomalous exponent scales to zero below the
one-particle crossover temperature. As a consequence, coherent quasiparticles
with finite weight appear along the whole Fermi surface. Extending the
expansion self-consistently to all orders turns out to be crucial in order to
restore the correct Fermi-liquid behavior.Comment: Shortened version to appear in Physical Review Letter
Nonuniversal spectral properties of the Luttinger model
The one electron spectral functions for the Luttinger model are discussed for
large but finite systems. The methods presented allow a simple interpretation
of the results. For finite range interactions interesting nonunivesal spectral
features emerge for momenta which differ from the Fermi points by the order of
the inverse interaction range or more. For a simplified model with interactions
only within the branches of right and left moving electrons analytical
expressions for the spectral function are presented which allows to perform the
thermodynamic limit. As in the general spinless model and the model including
spin for which we present mainly numerical results the spectral functions do
not approach the noninteracting limit for large momenta. The implication of our
results for recent high resolution photoemission measurements on quasi
one-dimensional conductors are discussed.Comment: 19 pages, Revtex 2.0, 5 ps-figures, to be mailed on reques
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