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S. Ajisaka

Publications and source records attributed to S. Ajisaka.

7 recordsLinked to original sources
arXiv2012

Current in coherent quantum systems connected to mesoscopic Fermi reservoirs

We study particle current in a recently proposed model for coherent quantum transport. In this model a system connected to mesoscopic Fermi reservoirs (meso-reservoir) is driven out of equilibrium by the action of super reservoirs thermalized to prescribed temperatures and chemical potentials by a simple dissipative mechanism described by the Lindblad equation. We compare exact (numerical) results with theoretical expectations based on the Landauer formula

cond-mat.stat-mech↗
arXiv2012

Nonequlibrium particle and energy currents in quantum chains connected to mesoscopic Fermi reservoirs

We propose a model of nonequilibrium quantum transport of particles and energy in a system connected to mesoscopic Fermi reservoirs (meso-reservoir). The meso-reservoirs are in turn thermalized to prescribed temperatures and chemical potentials by a simple dissipative mechanism described by the Lindblad equation. As an example, we study transport in monoatomic and diatomic chains of non-interacting spinless fermions. We show numerically the breakdown of the Onsager reciprocity relation due to the dissipative terms of the model.

cond-mat.mes-hall↗
arXiv2009

Polaron formation as a genuine nonequilibrium phenomenon

Solitons and polarons at nonequilibrium steady states are investigated for the spinless Takayama Lin-Liu Maki model. Polarons are found to be possible {\it only out of equilibrium}. This polaron formation is a genuine nonequilibrium phenomenon, as there is a lower threshold current below which they cannot exist. It is considered to be an example of microscopic dissipative structure.

cond-mat.stat-mech↗
arXiv2009

Static Soliton at Nonequilibrium Steady State

Nonequlibrium phase transition of an open Takayama-Lin Liu-Maki chain coupled with two reservoirs is investigated. We will show that solitons connecting two uniform phases are possible, and the amplitude of solitons obeys the same self-consistent equation as that of uniform phases.

cond-mat.stat-mech↗
arXiv2006

Reconnection of Unstable/Stable Manifolds of the Harper Map

The Harper map is one of the simplest chaotic systems exhibiting reconnection of invariant manifolds. The method of asymptotics beyond all orders (ABAO) is used to construct unstable/stable manifolds of the Harper map. By enlarging the neighborhood of a singularity, the perturbative solution of the unstable manifold is expressed as a Borel summable asymptotic expansion in a sector including $t=-\infty$ and is analytically continued to the other sectors, where the solution acquires new terms describing heteroclinic tangles. When the parameter changes to the reconnection threshold, the unstable/stable manifolds are shown to acquire new oscillatory portion corresponding to the heteroclinic tangle after the reconnection.

nlin.CD↗
arXiv2006

Method of Asymptotics beyond All Orders and Restriction on Maps

The method of asymptotics beyond all orders (ABAO) is known to be a useful tool to investigate separatrix splitting of several maps. For a class of simplectic maps, the form of maps is shown to be restricted by the conditions for the ABAO method to work well. More over, we check that the standard map, H\' enon map and the cubic map satisfy the restrcitions.

nlin.CD↗