1,323 research outputs found
Transient trapping into metastable states in systems with competing orders
The quench dynamics of a system involving two competing orders is
investigated using a Ginzburg-Landau theory with relaxational dynamics. We
consider the scenario where a pump rapidly heats the system to a high
temperature, after which the system cools down to its equilibrium temperature.
We study the evolution of the order parameter amplitude and fluctuations in the
resulting time dependent free energy landscape. Exponentially growing thermal
fluctuations dominate the dynamics. The system typically evolves into the phase
associated with the faster-relaxing order parameter, even if it is not the
global free energy minimum. This theory offers a natural explanation for the
widespread experimental observation that metastable states may be induced by
laser induced collapse of a dominant equilibrium order parameter.Comment: 12 pages, 7 figure
Floquet engineering of many-body states by the Ponderomotive potential
The Ponderomotive force is a static second order force that a particle feels
in an oscillating field, whose static potential may be called the Ponderomotive
potential. We generalize this notion to that for generic degrees of freedom in
periodically driven quantum many-body systems, and propose it as a convenient
tool to engineer the non-equilibrium steady states beyond the single particle
level. Applied to materials driven by light, the Ponderomotive potential is
intimately related to the optical conductivity, which is enhanced close to
resonances. We show that the Ponderomotive potential from the incident light
may be used to induce exciton condensates in semiconductors, to generate
attractive interactions leading to superconductivity in certain electron-phonon
systems, and to create additional free energy minima in systems with
charge/spin/excitonic orders. These effects are shown for realistic parameters
such that they can be readily verified in ultrafast experiments.Comment: 5 pages, 3 figure
Research on the Problems of Housing Prices in Qingdao from a Macro Perspective
Qingdao is a seaside city. Taking into account the characteristics of Qingdao, this article established a multiple linear regression model to analyze the impact of macroeconomic factors on housing prices. We used stepwise regression method to make multiple linear regression analysis, and made statistical analysis of F test values and T test values. According to the analysis results, the model is continuously optimized. Finally, this article obtained the multiple linear regression equation and the influencing factors, and the reliability of the model was verified by F test and T test
Universal linear and nonlinear electrodynamics of the Dirac fluid
A general relation is derived between the linear and second-order nonlinear
ac conductivities of an electron system in the hydrodynamic regime of
frequencies below the interparticle scattering rate. The magnitude and
tensorial structure of the hydrodynamic nonlinear conductivity are shown to
differ from their counterparts in the more familiar kinetic regime of higher
frequencies. Due to universality of the hydrodynamic equations, the obtained
formulas are valid for systems with an arbitrary Dirac-like dispersion, ranging
from solid-state electron gases to free-space plasmas, either massive or
massless, at any temperature, chemical potential or space dimension.
Predictions for photon drag and second-harmonic generation in graphene are
presented as one application of this theory.Comment: 5 pages, 4 figure
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