664 research outputs found
On the Nature of the `Quasiparticle' Peak in the Angular Resolved Spectrum of the Superconducting Underdoped BiSrCaCuO
We study the reconfiguration of the angular resolved photoemission spectrum
near point which occurs in BiSrCaCuO upon cooling below the
superconducting transition temperature. Restricting our attention to the case
of underdoped samples we offer a phenomenological mechanism-independent
argument which explains the emergence of a peak in the spectrum in terms of the
normal state pseudogap. All of the basic experimental observations, including
the peak dispersion, `dip-and-hump' shape of the superconducting state spectrum
and appearance of the peak at the temperatures somewhat higher than , are
naturally explained.Comment: 10 pages, 4 figure
Fermionic Quasiparticle Representation of Tomonaga-Luttinger Hamiltonian
We find a unitary operator which asymptotically diagonalizes the
Tomonaga-Luttinger hamiltonian of one-dimensional spinless electrons. The
operator performs a Bogoliubov rotation in the space of electron-hole pairs. If
bare interaction of the physical electrons is sufficiently small this
transformation maps the original Tomonaga-Luttinger system on a system of free
fermionic quasiparticles. Our representation is useful when the electron
dispersion deviates from linear form. For such situation we obtain
non-perturbative results for the electron gas free energy and the
density-density propagator.Comment: In the new version two new appendices are added, several errors and
misprints are corrected; 19 pages, 3 eps figure
The calculation of the impurity entropy for the exactly solvable two-channel Kondo model
In this paper the entropy of the two-channel Kondo impurity is calculated. We
demonstrate that the exactly solvable system of finite size can be described in
terms of free fermions. None of these fermions is Majorana fermion. This allows
us to find the impurity entropy for arbitrary values of and .
As found before, equals to . For finite the
entropy shows a cross-over to the infinite-size behavior at , in
agreement with results of other researchers.Comment: 4 pages, 1 figure, the title is changed, some changes in the paper
text, two references are adde
Generation of localized magnetic moments in the charge-density-wave state
We propose a mechanism explaining the generation of localized magnetic
moments in charge-density-wave compounds. Our model Hamiltonian describes an
Anderson impurity placed in a host material exhibiting the charge-density wave.
There is a region of the model's parameter space, where even weak Coulomb
repulsion on the impurity site is able to localize the magnetic moment on the
impurity. The phase diagram of a single impurity at T=0 is mapped. To establish
the connection with experiment thermodynamic properties of a random impurity
ensemble is studied. Magnetic susceptibility of the ensemble diverges at low
temperature; heat capacity as a function of the magnetic field demonstrates
pronounced low field peak. Both features are consistent with experiments on
orthorhombic TaS3 and blue bronze.Comment: 8 pages, 7 figure
The Interacting Impurity Josephson Junction: Variational Wavefunctions and Slave Boson Mean Field Theory
We investigate the Josephson coupling between two superconductors mediated
through an infinite U Anderson impurity, adapting a variational wavefunction
approach which has proved successful for the Kondo model. Unlike the Kondo
problem, however, a crossing of singlet and doublet state energies may be
produced by varying the ratio of Kondo energy to superconducting gap, in
agreement with recent work of Clerk and Ambegaokar. We construct the phase
diagram for the junction and discuss properties of different phases. In
addition, we find the singlet and doublet state energies within a slave boson
mean field approach. We find the slave boson mean field treatment is unable to
account for the level crossing.Comment: 5 pages; 4 encapsulated PostScript figures; submitted to Phys. Rev.
Possibility of Geometric Description of Quasiparticles in Solids
New phenomenological approach for the description of elementary collective
excitations is proposed. The crystal is considered to be an anisotropic
space-time vacuum with a prescribed metric tensor in which the information on
electromagnetic crystalline fields is included. The quasiparticles in this
space are supposed to be described by the equations structurally similar to the
relativistic wave equations for particles in empty space. The generalized
Klein-Gordon-Fock equation and the generalized Dirac equation in external
electromagnetic field are considered. The applicability of the proposed
approach to the case of conduction electron in a crystal is discussed.Comment: 17 pages, latex; to appear in Int. Jnl. Mod. Phy
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