• Trallero Giner, C. 1986-09-01 We use the effective-mass approximation to obtain the imaginary part, ε 2, of the dielectric constant of a quantum well in an applied electric field for direct transitions at a normal (M O ) threshold. The calculations of ε 2 are used to evaluate the real part, ε 1, of the dielectric constant through the Kramers-Kronig relations. The changes in ε 1 and ε 2 due to the electric field are expressed in terms of the corresponding electrooptic functions. All magnitudes are obtained, neglecting excitonic effects, for electric fields both perpendicular to and in the plane of the layers. We show that for fields parallel to the layers the electrooptic functions turn out to be a superposition of two-dimensional Franz- Keldysh ones. The electrooptic functions for fields perpendicular to the layers show a qualitatively different behaviour from those observed in bulk semiconductors.
Analytic expressions for the Lorentzian broadening of ε 1 and ε 2 are given in terms of complex valued electrooptic functions of complex argument. (author) • Su, Yuehua, E-mail: suyh@ytu.edu.cn 2016-03-01 Inelastic low-energy Raman and high-energy X-ray scatterings have made great progress in instrumentation to investigate the strong electronic correlations in matter.
However, theoretical study of the relevant scattering spectrum is still a challenge. In this paper, we present a Schwinger– Keldysh canonical perturbation formalism for the electronic Raman scattering, where all the resonant, non-resonant and mixed responses are considered uniformly. We show how to use this formalism to evaluate the cross section of the electronic Raman scattering off an one-band superconductor. All the two-photon scattering processes from electrons, the non-resonant charge density response, the elastic Rayleigh scattering, the fluorescence, the intrinsic energy-shift Raman scattering and the mixed response, are included. Dokladnaya zapiska na uchenika shkoli primer. In the mean-field superconducting state, Cooper pairs contribute only to the non-resonant response.
All the other responses are dominated by the single-particle excitations and are strongly suppressed due to the opening of the superconducting gap. Our formalism for the electronic Raman scattering can be easily extended to study the high-energy resonant inelastic X-ray scattering. • Sieberer, L M; Buchhold, M; Diehl, S 2016-09-01 Recent experimental developments in diverse areas-ranging from cold atomic gases to light-driven semiconductors to microcavity arrays-move systems into the focus which are located on the interface of quantum optics, many-body physics and statistical mechanics. They share in common that coherent and driven-dissipative quantum dynamics occur on an equal footing, creating genuine non-equilibrium scenarios without immediate counterpart in equilibrium condensed matter physics. This concerns both their non-thermal stationary states and their many-body time evolution. It is a challenge to theory to identify novel instances of universal emergent macroscopic phenomena, which are tied unambiguously and in an observable way to the microscopic drive conditions.
In this review, we discuss some recent results in this direction. Moreover, we provide a systematic introduction to the open system Keldysh functional integral approach, which is the proper technical tool to accomplish a merger of quantum optics and many-body physics, and leverages the power of modern quantum field theory to driven open quantum systems. • Bauer, Jaroslaw 2006-01-01 When a frequency of the circularly polarized laser field approaches zero the above threshold ionization rate should approach the well-known static-field limit of tunneling ionization. In the high-intensity limit of the laser field the Keldysh-Faisal-Reiss (KFR) theory is expected to be valid. For the ground state of a hydrogen atom we study various forms of the KFR theory when both conditions: ω ttabel = 2,032. Simpulan dari penelitian ini yakni prokrastinasi akademik dapat dikurangi melalui layanan penguasaan konten.
