| 1. |
- Moskalenko, S. A., et al.
(författare)
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Metastable bound states and spin structures of the two-dimensional bimagnetoexcitons
- 2018
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Ingår i: Advanced Topics in Optoelectronics, Microelectronics, and Nanotechnologies IX. - : SPIE - International Society for Optical Engineering. - 9781510626140
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Konferensbidrag (refereegranskat)abstract
- The bound states of two interacting two-dimensional magnetoexcitons with electrons and holes on the lowest Landau levels (LLLs) moving in-plane of the layer with equal but opposite oriented wave vectors and forming a molecular-type structures with the resultant wave vector (k) over right arrow = 0 were investigated. Four possible spin structures of two electrons and of two holes forming the bound states were considered. Two of them lead to the formation of the para and ortho magnetoexcitons in the presence of the electron-hole (e-h) Coulomb exchange interaction. In this case we have studied the interaction of two para magnetoexcitons and of two ortho magnetoexcitons with the resultant spin equal to zero. Another two variant, are actual when the Coulomb exchange e-h interaction is negligible small and the spin of two electrons separately and the effective spin of two holes are interconected and forms the singlet or the triplet states with zero spin projections on the magnetic field direction. The spin states of the four particles were constructed combining the singlet two electron state with the singlet two hole state as well as the triplet two electron state with the triplet two hole state. Only the bound states of two electrons and of two holes with singlet-singlet and with triplet-triplet spin structures were studied. It was shown that the spin structure of the type singlet-triplet and triplet-singlet do not exist due to the hidden symmetry of the magnetoexcitons. The orbital structure of the 2D magnetoexciton with wave vector (k) over right arrow not equal 0 is similar with an in-plane electric dipole with the dipole moment perpendicularly oriented to the wave vector. The bimagnetoexciton with resultant wave vector (k) over right arrow = 0 is composed from two antiparallel oriented electric dipoles moving with antiparallel wave vectors (k) over right arrow not equal 0 Their relative motion in the frame of the bound states is characterized by the variational wave functions phi(n) ((k) over right arrow) depending on the modulus vertical bar(k) over right arrow vertical bar. It was shown that the stable bound state in the lowest Landau levels approximation do not exist in four investigated spin combinations. Instead of them a deep metastable bound state with an activation barrier comparable with the ionization potential of the magnetoexciton with (k) over right arrow = 0 was revealed in the triplet-triplet spin configuration. Its orbital structure in the momentum space representation is characterized by the maximal exciton density on the in-plane ring and with zero density in the center.
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| 2. |
- Moskalenko, S. A., et al.
(författare)
-
Metastable bound states of the interacting two-dimensional magnetoexcitons
- 2018
-
Ingår i: Solid State Communications. - : Elsevier. - 0038-1098 .- 1879-2766. ; 283, s. 14-21
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Tidskriftsartikel (refereegranskat)abstract
- The possible formation of two-dimensional (2D) magnetic biexcitons composed of two 2D magnetoexcitons with electrons and holes on the lowest Landau levels (LLLs) with opposite center-of-mass wave vectors (k)over-right-arrow and -(k)over-right-arrow and with antiparallel electric dipole moments perpendicular to the corresponding wave vectors was investigated. Two spinor structures of two electrons and of two holes were considered. In the singlet-singlet state the spins of two electrons as well as the effective spins of two holes create the combinations with the total spin S = 0 and its projection on the magnetic field S-z = 0. The triplet-triplet state corresponds to S = 1 and S-z = 0. Two orbital Gaussian variational wave functions depending on vertical bar(k)over-right-arrow vertical bar and describing the relative motion of two magnetoexcitons inside the molecule were used. Analytical calculations show that in the LLLs approximation the stable bound states of bimagnetoexcitons do not exist, but there is a metastable bound state with the orbital wave function, having the maximum on the in-plane ring for the triplet-triplet spin configuration. The metastable bound state has an energy activation barrier comparable with the magnetoexciton ionization potential and gives rise to the new luminescence band due to the metastable biexciton-para exciton conversion with the frequencies higher than those of the para magnetoexciton luminescence line.
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| 3. |
- Moskalenko, S. A., et al.
(författare)
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Metastable Bound States of the Two-Dimensional Bimagnetoexcitons in the Lowest Landau Levels Approximation
- 2018
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Ingår i: Semiconductors (Woodbury, N.Y.). - : PLEIADES PUBLISHING INC. - 1063-7826 .- 1090-6479. ; 52:14, s. 1801-1805
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Tidskriftsartikel (refereegranskat)abstract
- The possible existence of the bound states of the interacting two-dimensional (2D) magnetoexcitons in the lowest Landau levels (LLLs) approximation was investigated using the Landau gauge description. The magnetoexcitons taking part in the formation of the bound state with resultant wave vector have opposite in-plane wave vectors and and look as two electric dipoles with the arms oriented in-plane perpendicularly to the corresponding wave vectors. The bound state of two antiparallel dipoles moving with equal probability in any direction of the plane with equal but antiparallel wave vectors is characterized by the variational wave function of the relative motion depending on the modulus . The spins of two electrons and the effective spins of two holes forming the bound states were combined separately in the symmetric or in the antisymmetric forms with the same parameter for electrons and holes. In the case of the variational wave function the maximum density of the magnetoexcitons in the momentum space representation is concentrated on the in-plane ring with the radius The stable bound states of the bimagnetoexciton molecule do not exist for both spin orientations. Instead of them, a deep metastable bound state with the activation barrier comparable with the ionization potential of the magnetoexciton with was revealed in the case and . In the case and only a shallow metastable bound state can appear.
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| 4. |
- Moskalenko, S. A., et al.
(författare)
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Influence of excited Landau levels on a two-dimensional electron-hole system in a strong perpendicular magnetic field
- 2006
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Ingår i: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 140:5, s. 236-239
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Tidskriftsartikel (refereegranskat)abstract
- The study of the quantum states of a two-dimensional electron-hole system in a strong perpendicular magnetic field is carried out with special attention to the influence of virtual quantum transitions of interacting particles between the Landau levels. These virtual quantum transitions from the lowest Landau levels to excited Landau levels with arbitrary quantum numbers n and m and their reversion to the lowest Landau levels in second order perturbation theory result in an indirect attraction between the particles. The influence of the indirect interaction on the magnetoexciton ground state, on the chemical potential of the Bose-Einstein condensed magnetoexcitons, and on the ground state energy of the metallic-type electron-hole liquid is investigated in the Hartree-Fock approximation. The coexistence of different phases is suggested.
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