170 research outputs found
Lattice electrons in constant magnetic field: Bethe like ansatz
We use the functional representation of Heisenberg-Weyl group and obtain
equation for the spectrum of the model, which is more complicated than Bethes
ones, but can be written explicitly through theta functions.Comment: 8 pages, LATE
Zero-bias tunneling anomaly in a clean 2D electron gas caused by smooth density variations
We show that smooth variations, \delta n({\bf r}), of the local electron
concentration in a clean 2D electron gas give rise to a zero-bias anomaly in
the tunnel density of states, \nu(\omega), even in the absence of scatterers,
and thus, without the Friedel oscillations. The energy width, \omega_0, of the
anomaly scales with the magnitude, \delta n, and characteristic spatial extent,
D, of the fluctuations as (\delta n/D)^{2/3}, while the relative magnitude
\delta\nu/\nu scales as (\delta n/D). With increasing \omega, the averaged
\delta\nu oscillates with \omega. We demonstrate that the origin of the anomaly
is a weak curving of the classical electron trajectories due to the smooth
inhomogeneity of the gas. This curving suppresses the corrections to the
electron self-energy which come from the virtual processes involving two
electron-hole pairsComment: 4+ pages, 3 figure
Smearing of the 2D Kohn anomaly in a nonquantizing magnetic field: Implications for the interaction effects
Thermodynamic and transport characteristics of a clean two-dimensional
interacting electron gas are shown to be sensitive to the weak perpendicular
magnetic field even at temperatures much higher than the cyclotron energy, when
the quantum oscillations are completely washed out. We demonstrate this
sensitivity for two interaction-related characteristics: electron lifetime and
the tunnel density of states. The origin of the sensitivity is traced to the
field-induced smearing of the Kohn anomaly; this smearing is the result of
curving of the semiclassical electron trajectories in magnetic field.Comment: 4.5 pages, 3 figures, published versio
An Integrable Model with non-reducible three particle R-Matrix
We define an integrable lattice model which, in the notation of Yang, in
addition to the conventional 2-particle -matrices also contains
non-reducible 3-particle -matrices. The corresponding modified Yang-Baxter
equations are solved and an expression for the transfer matrix is found as a
normal ordered exponential of a (non-local) Hamiltonian.Comment: 13 pages, 4 figure
The 3d Ising Model represented as Random Surfaces
We consider a random surface representation of the three-dimensional Ising
model.The model exhibit scaling behaviour and a new critical index \k which
relates \g_{string} for the bosonic string to the exponent \a of the
specific heat of the 3d Ising model is introduced. We try to determine \k by
numerical simulations.Comment: No figures included. Available by ordinary mail on request. 13 pages.
Latex. preprint NBI-HE-92-8
Graphene valley polarization as a function of carrier-envelope phase in few-cycle laser pulses and its footprints in harmonic signals
We consider coherent dynamics of graphene charged carriers exposed to an
intense few-cycle linearly polarized laser pulse. The results, obtained by
solving the generalized semiconductor Bloch equations numerically in the
Hartree-Fock approximation, taking into account many-body Coulomb interaction,
demonstrate strong dependence of the valley polarization on the
carrier-envelope phase (CEP), which is interpolated by the simple sinusoidal
law. Then we consider harmonic generation in multi-cycle laser field by
graphene preliminary exposed to an intense few-cycle laser pulse. We show that
the second harmonic's intensity is a robust observable quantity that provides a
gauge of CEP for pulse durations up to two optical cycles, corresponding to 40
at the wavelength of 6.2 .Comment: 9 pages, 10 figure
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