Probing anomalous relaxation by coherent multidimensional optical spectroscopy

We propose to study the origin of algebraic decay of two-point correlation functions observed in glasses, proteins, and quantum dots by their nonlinear response to sequences of ultrafast laser pulses. Power-law spectral singularities and temporal relaxation in two-dimensional correlation spectroscopy signals are predicted for a continuous time random walk model of stochastic spectral jumps in a two-level system with a power-law distribution of waiting times psi(t) approximately t;{-alpha-1}. Spectroscopic signatures of stationary ensembles for 1相似文献   

Slow relaxation in microcanonical warming of a Ising lattice

We study the warming process of a semi-infinite cylindrical Ising lattice initially ordered and coupled at the boundary to a heat reservoir. The adoption of a proper microcanonical dynamics allows a detailed study of the time evolution of the system. As expected, thermal propagation displays a diffusive character and the spatial correlations decay exponentially in the direction orthogonal to the heat flow. However, we show that the approach to equilibrium presents an unexpected slow behavior. In particular, when the thermostat is at infinite temperature, correlations decay to their asymptotic values by a power law. This can be rephrased in terms of a correlation length vanishing logarithmically with time. At finite temperature, the approach to equilibrium is also a power law, but the exponents depend on the temperature in a non-trivial way. This complex behavior could be explained in terms of two dynamical regimes characterizing finite and infinite temperatures, respectively. When finite sizes are considered, we evidence the emergence of a much more rapid equilibration, and this confirms that the microcanonical dynamics can be successfully applied on finite structures. Indeed, the slowness exhibited by correlations in approaching the asymptotic values are expected to be related to the presence of an unsteady heat flow in an infinite system.     

一维反激光器完美相干吸收理论分析

利用传输矩阵和散射矩阵方法, 具体计算了单通道和双通道结构完美相干吸收效应的产生条件, 并分析了其之间的相关性.结果表明, 单、双通道结构各自都有大量可选条件能促 使完美相干吸收效应的发生, 且在入射波长及其相应介质折射率等参数不变的情况下, 双通道完美相干吸收效应产生所对应的介质长度与单通道完美相干吸收效应产生所对应的 介质长度具有二倍关系.如波长为756 nm的光入射Si介质,完美相干吸收可以在介质长度分别为3.701 和7.402 μm的单通道结构和双通道结构中发生. 该研究对促进完美相干吸收效应在光调制、光开关、光学探测等方面应用以及光学通 信和计算领域的硅基集成光子器件设计都具有积极意义.     

Tunable coherent perfect absorption in three-dimensional Dirac semimetal films

In this article, we investigate the phenomenon of coherent perfect absorption(CPA) with bulk Dirac semimetal(BDS) thin film. CPA of BDS appears at the frequency of 43.89 THz with 0° phase modulation of two coherent input lights. Meanwhile, it shows that CPA can be realized under oblique incidence circumstances for both TM and TE polarizations. Moreover, the frequency of CPA can be adjusted by altering the thickness of BDS thin film, and the dynamic regulation of CPA can be realized by changing the Fermi energy. Finally, the peak coherent absorption frequency can be controlled by changing the degeneracy factor.     

Exact relaxation in a class of nonequilibrium quantum lattice systems

A reasonable physical intuition in the study of interacting quantum systems says that, independent of the initial state, the system will tend to equilibrate. In this work we introduce an experimentally accessible setting where relaxation to a steady state is exact, namely, for the Bose-Hubbard model quenched from a Mott quantum phase to the free strong superfluid regime. We rigorously prove that the evolving state locally relaxes to a steady state with maximum entropy constrained by second moments--thus maximizing the entanglement. Remarkably, for this to be true, no time average is necessary. Our argument includes a central limit theorem and exploits the finite speed of information transfer. We also show that for all periodic initial configurations (charge density waves) the system relaxes locally, and identify experimentally accessible signatures in optical lattices as well as implications for the foundations of statistical mechanics.     

Production of nanocrystal layers in monocrystal silicon in the beam-type plasma of a high-voltage discharge

The results of investigations on the formation of nanostructured hydrogen–silicon complexes in the nearsurface layer of monocrystal silicon exposed to hydrogen-containing plasma are presented. By using infrared and Auger spectroscopy, it has been shown that the formation of nanolayers and, hence, an extreme change of the resistivity of the near-surface layer take place only at short treatment times.     

Studies of molecular relaxation by infrared and microwave coherent transients

Novel techniques to observe coherent transients are successfully demonstrated on microwave transitions of NH₃, H₂O, OCS, and O₂. The relaxation rate constants in thev ₂ excited state of NH₃ are obtained by infrared experiments. Paper was prepared for presentation at FICOLS.     

On structural defect generation induced by thermal fluctuations in materials with a perfect lattice under dynamic loading

The possibility of structural defect generation induced by thermal fluctuations in single crystals under high-rate deformation is numerically investigated. It is shown that thermal fluctuations can be a reason for structural defect generation and there is a threshold strain value at which zones with local structural changes grow almost abruptly.     

Critical relaxation of the temperature in a square lattice Ising system

The critical dynamics of an energy-like perturbation in a square Ising spin system is studied by the real space renormalization group approach. The critical exponent is 2.14 in the cumulant expansion and 2.29 in the potential moving approximations.     

Hyperbolic relaxation as a sufficient condition of a fully coherent ergodic field

In three cases, one originating from a classical model, the second from the time-evolution operator, and the third from photocount statistics, it is shown that an initially excited coherent field which remains coherent in time development relaxes according to a hyperbolic rather than to an exponential law. This has particular relevance for the analysis of biological systems.     

Fractal patterns on the onset of coherent structures in a coupled map lattice

We report the formation of Cantor set-like fractals during the development of coherent structures in a coupled map lattice (CML). The dependence of these structures on the size of the lattice as well as the first three dimensions of the associated fractal patterns are analyzed numerically.     

Spin — lattice relaxation in chlorofluorocarbon liquids

We have used the spin — echo method to measure spin — lattice relaxation times in liquid chlorofluorocarbons over a wide range of temperatures, frequencies, and molecular weights. Analysis of the experimental data shows that to determine the kinetic parameters of viscous liquids it is necessary to use the theory of nuclear magnetic relaxation by translational diffusion. We describe a method for the computer calculation of these parameters and discuss the results.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 46–51, March, 1976.     

Charge relaxation and instability in barrier layers

It is shown experimentally that the order of magnitude of the relaxation time of a physical barrier layer is determined by the product of the Maxwell relaxation time and the corresponding exponent. The experiments deal with dielectric dispersion in ferrites and nickel oxide. It is shown that near the relaxation maximum these inhomogeneous semiconductors can be considered as quasihomogeneous. A new treatment of a number of instabilities in barrier layers is presented: low frequency voltage fluctuations in p—n junctions and Schottky barriers, barrier instability, etc.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 20–23, June, 1981.