Browsing by Author "Hakioglu, T."
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Item Open Access The Influence of the Rashba spin orbit coupling on the two dimensional magnetoexcitons(IOP Publishing, 2011) Hakioglu, T.; Liberman, M. A.; Moskalenko, S. A.; Podlesny, I. V.The influence of the Rashba spin-orbit coupling (RSOC) on the two-dimensional (2D) electrons and holes in a strong perpendicular magnetic field leads to different results for the Landau quantization in different spin projections. In the Landau gauge the unidimensional wave vector describing the free motion in one in-plane direction is the same for both spin projections, whereas the numbers of Landau quantization levels are different. For an electron in an s-type conduction band they differ by one, as was established earlier by Rashba (1960 Fiz. Tverd. Tela 2 1224), whereas for heavy holes in a p-type valence band influenced by the 2D symmetry of the layer they differ by three. The shifts and the rearrangements of the 2D hole Landau quantization levels on the energy scale are much larger in comparison with the case of conduction electron Landau levels. This is due to the strong influence of the magnetic field on the RSOC parameter. At sufficiently large values of this parameter the shifts and rearrangements are comparable with the hole cyclotron energy. There are two lowest spin-split Landau levels for electrons as well as four lowest ones for holes in the case of small RSOC parameters. They give rise to eight lowest energy bands of the 2D magnetoexcitons, as well as of the band-to-band quantum transitions. It is shown that three of them are dipole-active, three are quadrupole-active and two are forbidden. The optical orientation under the influence of circularly polarized light leads to optical alignment of the magnetoexcitons with different orbital momentum projections in the direction of the external magnetic field.Item Open Access The Moyal-Lie theory of phase space quantum mechanics(Institute of Physics, 2001) Hakioglu, T.; Dragt, A. J.A Lie algebraic approach to the unitary transformations in Weyl quantization is discussed. This approach, being formally equivalent to the (black star)-quantization, is an extension of the classical Poisson-Lie theory and can be used as an efficient tool in the quantum phase space transformation theory.Item Open Access Non-local, non-commutative picture in quantum mechanics and distinguished continuous canonical maps(IOP Science, 2002) Hakioglu, T.It is shown that continuous classical nonlinear canonical (Poisson) maps have a distinguished role in quantum mechanics. They act unitarily on the quantum phase space and generate h-independent quantum nonlinear canonical maps. It is also shown that such maps act in the non-commutative phase space under the classical covariance. A crucial result of the work is that under the action of Poisson maps a local quantum mechanical picture is converted onto a non-local picture which is then represented in a non-local Hilbert space. On the other hand, it is known that a non-local picture is equivalent by the Weyl map to a non-commutative picture which, in the context of this work, corresponds to a phase space formulation of the theory. As a result of this equivalence, a phase space Schrödinger picture can be formulated. In particular, we obtain the *-genvalue equation of Fairlie [Proc. Camb. Phil. Soc., 60, 581 (1964)] and Curtright, Fairlie and Zachos [Phys. Rev., D 58, 025002 (1998)]. In a non-local picture entanglement becomes a crucial concept. The connection between the entanglement and non-locality is explored in the context of Poisson maps and specific examples of the generation of entanglement from a local wavefunction are provided by using the concept of generalized Bell states. The results obtained are also relevant for the non-commutative soliton picture in the non-commutative field theories. We elaborate on this in the context of the scalar non-commutative field theory.Item Open Access Phonon squeezing in superconducting borocarbides(Elsevier BV * North-Holland, 1994) Hakioglu, T.; Ivanov, V. A.; Shumovsky, A. S.; Tanatar, BilalThe recently discovered superconductor LuNi2B2C is investigated in the context of strong electron-electron correlations modulated by a squeezed phonon mode propagating in the perpendicular direction to the layers with longitudinal polarization. The squeezed phonons arise in the anharmonic lattice expansion since the linear electron-phonon interaction vanishes due to the structure of the NiB4 tetrahedra. The observed weak isotope effect and small dependence of Tc on pressure is qualitatively understood within the framework of this model. © 1994.Item Open Access Radiative Dark-Bright Instability and Critical Casimir Effect in DQW Exciton Condensates(Elsevier, 2011) Hakioglu, T.; Özgün E.It is already well known that radiative interband interaction in the excitonic normal liquid in semiconducting double quantum wells is responsible for a negligible splitting between the energies of the dark and bright excitons enabling us to consider a four fold spin degeneracy. This has also lead many workers to naively consider the same degeneracy in studying the condensate. On the other hand, the non-perturbative aspects of this interaction in the condensed phase, e.g. its consequences on the order parameter and the dark-bright mixture in the ground state have not been explored. In this work, we demonstrate that the ground state concentrations of the dark and the bright exciton condensates are dramatically different beyond a sharp interband coupling threshold where the contribution of the bright component in the ground state vanishes. This shows that the effect of the radiative interband interaction on the condensate is nonperturbative. We also observe in the free energy a discontinuous derivative with respect to the layer separation at the entrance to the condensed phase, indicating a strong critical Casimir force. An estimate of its strength shows that it is measurable. Measuring the Casimir force is challenging, but at the same time it has a conclusive power about the presence of the long sought for condensed phase.