Найдено научных статей и публикаций: 1, для научной тематики: SYMMETRY BREAKING
1.
S. A. Moskalenko, M. A. Liberman, E. V. Dumanov, and E. S. Moskalenko
- American Scientific Publishers , 2013
The spontaneous breaking of the continuous symmetries of the two-dimensional (2D) electron–hole
systems in a strong perpendicular magnetic field leads to the formation of new ground states and
determines the energy spectra of the collective elementary excitations appearing over these ground
states. ...
The spontaneous breaking of the continuous symmetries of the two-dimensional (2D) electron–hole
systems in a strong perpendicular magnetic field leads to the formation of new ground states and
determines the energy spectra of the collective elementary excitations appearing over these ground
states. In this review the main attention is given to the electron–hole systems forming coplanar
magnetoexcitons in the Bose-Einstein condensation (BEC) ground state with the wave vector k =0,
taking into account the excited Landau levels, when the exciton-type elementary excitations coexist
with the plasmon-type oscillations. At the same time properties of the two-dimensional electron gas
(2DEG) spatially separated as in the case of double quantum wells (DQWs) from the 2D hole gas
under conditions of the fractional quantum Hall effect (FQHE) are of great interest because they
can influence the quantum states of the coplanar magnetoexcitons when the distance between
the DQW layers diminishes. We also consider in this review the bilayer electron systems under
conditions of the FQHE with the one half filling factor for each layer and with the total filling factor
for two layers equal to unity because the coherence between the electron states in two layers is
equivalent to the formation of the quantum Hall excitons (QHExs) in a coherent macroscopic state.
This makes it possible to compare the energy spectrum of the collective elementary excitations of
the Bose-Einstein condensed QHExs and coplanar magnetoexcitons. The breaking of the global
gauge symmetry as well as of the continuous rotational symmetries leads to the formation of the
gapless Nambu-Goldstone (NG) modes while the breaking of the local gauge symmetry gives rise
to the Higgs phenomenon characterized by the gapped branches of the energy spectrum. These
phenomena are equivalent to the emergence of massless and of massive particles, correspondingly,
in the relativistic physics. The application of the Nielsen-Chadha theorem establishing the number of
the NG modes depending of the number of the broken symmetry operators and the elucidation when
the quasi-NG modes appear are demonstrated using as an example related with the BEC of spinor
atoms in an optical trap. They have the final aim to better understand the results obtained in the
case of the coplanar Bose-Einstein condensed magnetoexcitons. The Higgs phenomenon results
in the emergence of the composite particles under the conditions of the FQHE. Their description
in terms of the Ginzburg-Landau theory is remembered. The formation of the high density 2D
magnetoexcitons and magnetoexciton-polaritons with point quantum vortices attached is suggested.
The conditions in which the spontaneous coherence could appear in a system of indirect excitons
in a double quantum well structures are discussed. The experimental attempts to achieve these
conditions, the main results and the accumulated knowledge are reviewed.
J. Nanoelectron. Optoelectron. 2012, Vol. 7, No. 7