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Projector-based renormalization approach to electron-hole-photon systems in their nonequilibrium steady state
摘要： We present an extended version of the projector-based renormalization method that can be used to address not only equilibrium but also nonequilibrium situations in coupled fermion-boson systems. The theory is applied to interacting electrons, holes, and photons in a semiconductor microcavity, where the loss of cavity photons into vacuum is of particular importance. The method incorporates correlation and fluctuation processes beyond mean-field theory in a wide parameter range of detuning, Coulomb interaction, light-matter coupling, and damping, even in the case when the number of quasiparticle excitations is large. This enables the description of exciton and polariton formation and their possible condensation through spontaneous phase symmetry breaking by analyzing the ground-state, steady-state, and spectral properties of a rather generic electron-hole-photon Hamiltonian, which also includes the coupling to two fermionic baths and a free-space photon reservoir. Thereby, the steady-state behavior of the system is obtained by evaluating expectation values in the long-time limit by means of the Mori-Zwanzig projection technique. Tracking and tracing different order parameters, the fully renormalized single-particle spectra and the steady-state luminescence, we demonstrate the Bose-Einstein condensation of excitons and polaritons and its smooth transition when the excitation density is increased.
关键词： exciton condensation,nonequilibrium steady state,semiconductor microcavity,projector-based renormalization method,electron-hole-photon systems,Bose-Einstein condensation,polariton condensation
更新于2025-09-23 15:23:52
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Accurate Number Densities of Ideal Photons in a One-Dimensional Barrel Cavity
摘要： Our experimental scheme is based on a barrel optical microcavity filled with a dye solution. It is found that the number of non-condensed photons is characterized by an analytical function, which involves a q-digamma function in mathematics. We employ the q-digamma function to calculate the spatial and momentum distributions of ideal photons in a one-dimensional barrel cavity. The first main finding in this paper is that the spatial and momentum distributions possess a similar profile. The second main finding is that when photons are in the normal state, the density profile exhibits Friedel oscillations. The third main finding is that when photons are in the BEC state, the density profile exhibits a sharp peak with extremely narrow width. The fourth main finding is that the central peak of the density distribution is a monotonically increasing function of the photon number N but is a monotonically decreasing function of the temperature T.
关键词： Bose-Einstein condensation,One-dimensional photons,Number densities of photons,Optical microcavity
更新于2025-09-23 15:23:52
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Dipolar Quantum Mixtures of Erbium and Dysprosium Atoms
摘要： We report on the first realization of heteronuclear dipolar quantum mixtures of highly magnetic erbium and dysprosium atoms. With a versatile experimental setup, we demonstrate binary Bose-Einstein condensation in five different Er-Dy isotope combinations, as well as one Er-Dy Bose-Fermi mixture. Finally, we present first studies of the interspecies interaction between the two species for one mixture.
关键词： erbium,dipolar quantum mixtures,Bose-Einstein condensation,interspecies interaction,dysprosium
更新于2025-09-23 15:21:21
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Few trapped quantum dipoles: quantum versus classical structures
摘要： We analyze the ground state of a two-dimensional quantum system of a few strongly con?ned dipolar bosons. Dipoles arrange in different stable structures that depend on the tilting polarization angle and the anisotropy of the con?ning trap. To this end, we use the exact diffusion Monte Carlo method and the quantum results are compared with classical ones obtained by stochastic optimization using simulated annealing. We establish the stability domains for the different patterns and estimate the transition boundaries delimiting them. Our results show signi?cant differences between the classical and quantum regimes which are mainly due to the quantum kinetic energy.
关键词： dipolar systems,Bose–Einstein condensation,quantum Monte Carlo,few-body physics
更新于2025-09-23 15:21:01
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - The Role of Trap Symmetry in an Atom-Chip Interferometer above the Bose-Einstein Condensation Threshold
摘要： Cold atom interferometers have demonstrated excellent performance and hold great prospects for time, gravity, acceleration and rotation measurements. Trapped interferometers, for example using atom chips, can potentially enable portable applications of theses sensors. Atom chip interferometers have been successfully demonstrated using Bose-Einstein condensates but are subject to the effect of atom-atom interactions which cause phase decoherence. In this study, we proposed an atom chip interferometer using a gas just above the condensation threshold to reduce the interaction effects. This proposal is similar to white light interferometry in the sense that the difference between the optical paths of the two arms must be close to zero to observe fringes. In a trapped interferometer this condition is analogous to maximizing the degree of symmetry between the two trapping potentials. We demonstrated that if the two trapping potentials are harmonic with slightly different curvatures inhomogeneous dephasing arises. This leads to a typical contrast decay time. Here we use 87Rb in the two states |a>=|F=1,mF=-1> and |b>=|F=2,mF=2>. Both states are trapped by the same magnetic field created by an atom chip. As described by the Breit-Rabi formula, the energies of the two levels |a> and |b> have a slightly different magnetic field dependence. We can use this difference to fine tune the curvature difference between the two trapping potentials. We perform Ramsey sequences and record the fringes as a function of the Ramsey time for several temperatures and values of curvature difference. We find a good agreement with the above formula. Coherence times of order 1s have been observed. We will describe the experiment, the model used to extract the contrast decay time and the limitations of this model due to atom interactions. The results open the way for experimental demonstration of atom chip accelerometers and gyroscopes.
关键词： trap symmetry,Ramsey sequences,atom-chip interferometer,Bose-Einstein condensation,coherence times
更新于2025-09-11 14:15:04
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Photoluminescence properties of the entire excitonic series in
摘要： We investigated the photoluminescence spectra of Cu2O under photoexcitation at 3.05 eV across the violet band gap. The following three features were found: photoluminescence from blue and violet excitons; photoluminescence from yellow excitons of s, d, and f states in addition to p states with a quantum number up to ten; and emissions associated with the inelastic collision of the 1s yellow excitons. The first process is relevant for the separation of radiative and nonradiative decay rates. The second process likely indicates radiative enhancement of high Rydberg yellow excitons. The last process verifies up-conversion of 1s yellow paraexcitons into higher Rydberg states, which is a critical factor impeding the realization of a high-density paraexciton gas towards transition to the Bose-Einstein condensation.
关键词： photoluminescence,Rydberg states,excitons,Bose-Einstein condensation,Cu2O
更新于2025-09-10 09:29:36