For the first time optically detected cyclotron resonance (ODCR) has been demonstrated using a CO, pumped far-infrared (FIR) laser instead of mircowaves. Both the electron and the light-hole cyclotron resonances have been observed in GaAs, as well as the 1 S to 2p + impurity transitions. Valence band quantum effects, well known in Ge, are resolved directly for the first time in GaAs and the electron cyclotron resonances show strong spin doublet in the highest quality MBE samples. The technique has remarkable resolution and sensitivity at low temperatures and, by constrast with other techniques that have been reported, we also observe the n = 1 to 2 (polaron shifted) and higher spin doublet split resonances at helium temperatures and with low FIR laser power. The conduction band results are analysed on the five-band model and the implications of this model on the valence band results are discussed. We have determined the valence band inverse mass parameters to be: ;' , = 7.5, 7, = 2.6, y3 = 3.1, K = 1.0.
Novel far-infrared optically detected cyclotron resonance (FIR-ODCR) techniques are used to investigate GaAs epilayers and t h e resuits are compared with conventional cyclotron resonance performed at far-infrared frequencies and ODCR at microwave frequencies. The FIROOCR technique shows remarkable resolution and sensitivity and has been applied to investigations of t h e electronic structure of low-dimensional systems. In particular. cyclotron resonance has been optically detected in a GaAsIGaAIAs multiple quantum well ( M a w ) sample and compared with ODCR results performed at microwave frequency. Multi-single quantum wells (MSOW) in an MBE GaAsIGaAIAs structure with different well thicknesses have also been investigated, and by detecting cyclotron resonance via the.FlR-induced changes in the luminescence of the separate wells, the power of the technique to investigate the cyclotron resonance mass versus well thickness in a single sample has been demonstrated. Finally. t h e experimentally determined values of effective mass for different well widths are compared with the theoretical results, showing good agreement.
We report the first direct measurements of the conduction band electron effective mass in MBE grown A10.481n0.52As on InP by t h e technique of optically detected cyclotron resonance (ODCR). The effective mass value derived is rn*=O.lOrnofO.O1rno. A value for the carrier momentum relaxation time is also deduced, indicating a lattice-limited mobility for this material of the order
We use a non-perturbative, space-time resolved, simulation of quantum electrodynamics to explore the properties of electrons dressed with photons. We observe differences in the dynamics of dressed and bare electron wave packets, including differences in dispersion, speed, and mass. These differences depend on the number of dressing photons. We also highlight other applications of the simulation.OCIS codes: 000.6800, 270.5580.In quantum electrodynamics energy eigenstates of the Hamiltonian are particles. Physical, or dressed, particles are eigenstates of the full Hamiltonian including the interaction between fermions and photons. Bare particles on the other hand are the energy eigenstates of the noninteracting terms of the Hamiltonian. Dressed particles are in general superpositions of bare particle states. For instance a dressed electron is an bare electron together with virtual electronpositron pairs and photons.We study the properties of dressed electrons in quantum electrodynamics through numerical simulation. The simulation evolves a specified wavefunction under a modified version of the usual QED Hamiltonian. The first modification is the decoupling of a chosen spatial dimension from the other two, which has the effect of restricting the dynamics to the single chosen spatial dimension. We also decouple positrons from the system and limit the electron and photon occupation numbers. These modifications are essentially no more than reductions of our state space, which allow for feasible computations.Studies similar to ours have focused on fermions dressed by massive scalar bosons [1, 2]. By constrast, in our use of the QED Hamiltonian we are simulating fermions (electrons) dressed by massless vector bosons (photons). We construct dressed electron wave packets from bare electron wave packets by replacing eigenstates of the Hamiltonian without interaction with the corresponding eigenstates of the Hamiltonian with interaction. We observe that these dressed electron wave packets are like their bare counterparts but surrounded by a probability cloud of photons.A simulated electron dressed with one photon has a lower rest energy than the associated bare electron. Allowing the electron in the simulation to be dressed by two photons results in a dressed particle with an even lower rest energy. The computational resources necessary to simulate a dressed electron scale very rapidly with the number of dressing photons. Dressing by a greater number of photons than two is computationally much harder and has not been pursued here. A bare electron, not being an eigenstate evolves nontrivially in time under the action of the Hamiltonian. We observe that a bare electron, allowed to evolve, quickly becomes surrounded by cloud of photons, effectively dressing itself. Along with this dynamical dressing of the electron, photons are radiated in either direction from the electron.The simulation allows us to compare the dynamics of dressed electrons with those of bare electrons. We find differences between the propagation of dressed a...
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