Quasi-polaritons in Bose–Einstein condensates induced by Casimir–Polder interaction with graphene (original) (raw)
Related papers
Bose-Einstein condensation of quasiparticles in graphene
Nanotechnology, 2010
The collective properties of different quasiparticles in various graphene-based structures in a high magnetic field have been studied. We predict Bose-Einstein condensation (BEC) and the superfluidity of 2D spatially indirect magnetoexcitons in a two-layer graphene. The superfluid density and the temperature of the Kosterlitz-Thouless phase transition are shown to be increasing functions of the excitonic density but decreasing functions of a magnetic field and the interlayer separation. The instability of the ground state of the interacting 2D indirect magnetoexcitons in a slab of superlattice with alternating electron and hole graphene layers (GLs) is established. The stable system of indirect 2D magnetobiexcitons, consisting of a pair of indirect excitons with antiparallel dipole moments, is considered in a graphene superlattice. The superfluid density and the temperature of the Kosterlitz-Thouless phase transition for magnetobiexcitons in a graphene superlattice are obtained. Moreover, the BEC of excitonic polaritons in a GL embedded in a semiconductor microcavity in a high magnetic field is predicted. While the superfluid phase in this magnetoexciton polariton system is absent due to a vanishing magnetoexciton-magnetoexciton interaction in a single layer in the limit of a high magnetic field, the critical temperature of the BEC formation is calculated. The observation of the BEC and superfluidity of 2D quasiparticles in graphene in a high magnetic field would be interesting confirmation of the phenomena we have described.
Bose-Einstein condensation of polaritons in graphene in a high magnetic field
2009
The Bose-Einstein condensation (BEC) of magnetoexcitonic polaritons in a graphene layer embedded in a optical microcavity in a high magnetic field B is predicted. The essential property of this system (in contrast, e.g., to a quantum well embedded in a cavity) is stronger influence of magnetic field and weaker influence of disorder. A two-dimensional (2D) magnetoexcitonic polaritons gas is considered in a planar harmonic electric field potential applied to excitons or a parabolic shape of the optical cavity causing the trapping of microcavity photons. It is shown that the effective polariton mass M eff increases with magnetic field as B 1/2 . The BEC critical temperature T (0) c decreases as B −1/4 and increases with the spring constant of the parabolic trap. The Rabi splitting related to the creation of a magnetoexciton in a high magnetic field in graphene is obtained. PACS numbers: 71.36.+c, 03.75.Hh, 73.20.Mf, 73.21.Fg In the past decade, Bose coherent effects of 2D excitonic polaritons in a quantum well embedded in a semiconductor microcavity have been the subject of theoretical and experimental studies . To obtain polaritons, two mirrors placed opposite each other form a microcavity, and quantum wells are embedded within the cavity at the antinodes of the confined optical mode. The resonant exciton-photon interaction results in the Rabi splitting of the excitation spectrum. Two polariton branches appear in the spectrum due to the resonant exciton-photon coupling. The lower polariton (LP) branch of the spectrum has a minimum at zero momentum. Recently, the polaritons in a harmonic potential trap have been studied experimentally in a GaAs/AlAs quantum well embedded in a GaAs/AlGaAs microcavity . In this trap, the exciton energy is shifted using a stress-induced band-gap. In this system, evidence for the BEC of polaritons in a quantum well has been observed . The theory of the BEC and superfluidity of exciton polaritons in a quantum well (QW) without magnetic field in a parabolic trap has been developed in Ref. .
Acoustic analog to the dynamical casimir effect in a bose-einstein condensate
Physical Review Letters, 2012
We have modulated the density of a trapped Bose-Einstein condensate by changing the trap stiffness, thereby modulating the speed of sound. We observe the creation of correlated excitations with equal and opposite momenta, and show that for a well defined modulation frequency, the frequency of the excitations is half that of the trap modulation frequency.
Acoustic Casimir effect for Graphene
arXiv: Mesoscale and Nanoscale Physics, 2017
By applying a new technique, we obtain the acoustic Casimir energy, for a few-layer Graphene membrane suspended over a rectangular trench, at finite temperature, and the Casimir forces are interpreted as temperature-dependent correction terms to the built-in (surface) tensions of the membrane. We show that these corrections generally break the tensional isotropy of the membrane, and can increase or decrease the membrane tension. We demonstrate that for a rectangular trench with side-lengths both in the order of few micrometers, these temperature corrections are negligible ($\sim 10^{-10} N/m$), while for a narrow rectangular trench with side-lengths in the order of few nanometers and few micrometers, these corrections are expected to be noticeable ($\sim 10^{-4} N/m$) at the room temperature. These temperature corrections would be even more considerable by increasing the purity and/or the temperature of the Graphene membrane. Consequently we introduce a corrected version for the fun...
Bose-Einstein condensate near a surface: Quantum field theory of the Casimir-Polder interaction
Physical Review A, 2010
We derive an expression for the collective Casimir-Polder interaction of a trapped gas of condensed bosons with a plane surface through the coupling of the condensate atoms with the electromagnetic field. A systematic perturbation theory is developed based on a diagrammatic expansion of the electromagnetic self-energy. In the leading order, the result for the interaction-energy is proportional to the number of atoms in the condensate mode. At this order, atom-atom interactions and recoil effects lead to corrections compared to the single-atom theory, through shifts of the atomic transition energies. We also discuss the impact of the spatial delocalization of the condensate mode.
Casimir energy for acoustic phonons in graphene
EPL (Europhysics Letters)
We find the Casimir energy, at finite temperature, for acoustic phonons in a Graphene sheet suspended over a rectangular trench, and the corresponding Casimir forces are interpreted as correction terms to the built-in tensions of the Graphene. We show that these corrections generally break the tensional isotropy of the membrane, and can increase or decrease the membrane tension. We demonstrate that for a narrow rectangular trench with side-lengths in the order of few nanometers and few micrometers, these temperature corrections are expected to be noticeable (∼ 10 −4 N/m) at the room temperature. These corrections would be even more considerable by increasing the temperature, and can be applied for adjusting the built-in tension of the Graphene. Consequently we introduce a corrected version for the fundamental resonance frequency of the Graphene resonator.
Bose-Einstein condensation and superfluidity of magnetoexcitons in bilayer graphene
Physical Review B, 2008
We propose the Bose-Einstein condensation (BEC) and superfluidity of quasi-two-dimensional (2D) spatially indirect magnetobiexcitons in a slab of superlattice with alternating electron and hole layers consisting from the semiconducting quantum wells (QWs) and graphene superlattice in high magnetic field. The two different Hamiltonians of a dilute gas of magnetoexcitons with a dipole-dipole repulsion in superlattices consisting of both QWs and graphene layers in the limit of high magnetic field have been reduced to one effective Hamiltonian a dilute gas of two-dimensional excitons without magnetic field. Moreover, for N excitons we have reduced the problem of 2N × 2 dimensional space onto the problem of N × 2 dimensional space by integrating over the coordinates of the relative motion of an electron (e) and a hole (h). The instability of the ground state of the system of interacting two-dimensional indirect magnetoexcitons in a slab of superlattice with alternating electron and hole layers in high magnetic field is established. The stable system of indirect quasi-two-dimensional magnetobiexcitons, consisting of pair of indirect excitons with opposite dipole moments is considered. The density of superfluid component ns(T ) and the temperature of the Kosterlitz-Thouless phase transition to the superfluid state in the system of two-dimensional indirect magnetobiexcitons, interacting as electrical quadrupoles, are obtained for both QW and graphene realizations.
Nonlinear vortex-phonon interactions in a Bose–Einstein condensate
Journal of Physics B: Atomic, Molecular and Optical Physics, 2016
We consider the nonlinear coupling between an exact vortex solution in a Bose-Einstein condensate and a spectrum of elementary excitations in the medium. These excitations, or Bogoliubov-de Gennes modes, are indeed a special kind of phonons. We treat the spectrum of elementary excitations in the medium as a gas of quantum particles, sometimes also called bogolons. An exact kinetic equation for the bogolon gas is derived, and an approximate form of this equation, valid in the quasi-classical limit, is also obtained. We study the energy transfer between the vortex and the bogolon gas, and establish conditions for vortex instability and damping.
2007
We propose the Bose-Einstein condensation (BEC) and superfluidity of quasi-two-dimensional (2D) spatially indirect magnetobiexcitons in a slab of superlattice with alternating electron and hole layers consisting from the semiconducting quantum wells (QWs) and graphene superlattice in high magnetic field. The two different Hamiltonians of a dilute gas of magnetoexcitons with a dipole-dipole repulsion in superlattices consisting of both QWs and graphene layers in the limit of high magnetic field have been reduced to one effective Hamiltonian a dilute gas of two-dimensional excitons without magnetic field. Moreover, for N excitons we have reduced the problem of 2N × 2 dimensional space onto the problem of N × 2 dimensional space by integrating over the coordinates of the relative motion of an electron (e) and a hole (h). The instability of the ground state of the system of interacting two-dimensional indirect magnetoexcitons in a slab of superlattice with alternating electron and hole layers in high magnetic field is established. The stable system of indirect quasi-two-dimensional magnetobiexcitons, consisting of pair of indirect excitons with opposite dipole moments is considered. The density of superfluid component ns(T) and the temperature of the Kosterlitz-Thouless phase transition to the superfluid state in the system of two-dimensional indirect magnetobiexcitons, interacting as electrical quadrupoles, are obtained for both QW and graphene realizations.
Casimir force on an interacting Bose-Einstein condensate
Journal of Physics B-atomic Molecular and Optical Physics, 2010
We have presented an analytic theory for the Casimir force on a Bose-Einstein condensate (BEC) which is confined between two parallel plates. We have considered Dirichlet boundary conditions for the condensate wave function as well as for the phonon field. We have shown that, the condensate wave function (which obeys the Gross-Pitaevskii equation) is responsible for the mean field part of Casimir force, which usually dominates over the quantum (fluctuations) part of the Casimir force.