arXiv subjects

Shuichi Tasaki

Publications and source records attributed to Shuichi Tasaki.

13 recordsLinked to original sources

arXiv2011

Quantum statistical mechanics in infinitely extended systems ($C^*$ algebraic approach)

The derivation of macroscopic irreversible dynamics of nonequilibrium systems from microscopic equations was recently revisited from the point of view of infinitely extended quantum systems. Here we have briefly reviewed the $C^*$ algebra and its application to equilibrium systems as well as introduced some recent results on NESS. In addition, we have demonstrated the derivation of Landauer formula rigorously for quadratic systems but using a more physical presentation.

math-ph↗

arXiv2010

Multifractal Wave Functions of a System with a Monofractal Energy Spectrum

We show the appearance of multifractal wave functions on a one-dimensional quasiperiodic system that has a monofractal energy spectrum. Using the Mantica technique, we construct the model as an inverse problem from the energy spectrum of a pure Cantor set. A relation between the critical state and the information dimension is proved and it is applied to the finite-size multifractal analysis.

cond-mat.stat-mech↗

arXiv2009

Entanglement of Electrons Field-Emitted from a Superconductor

Under appropriate circumstances the electrons emitted from a superconducting tip can be entangled. We analyze these nonlocal correlations by studying the coincidences of the field-emitted electrons and show that electrons emitted in opposite directions violate Bell's inequality. We scrutinize the interplay between the bosonic nature of Cooper pairs and the fermionic nature of electrons. We further discuss the feasibility of our analysis in the light of present experimental capabilities.

quant-ph↗

arXiv2009

Nonequilibrium Peierls Transition

Nonequlibrium phase transition of an open Takayama-Lin Liu-Maki chain coupled with two reservoirs is investigated by combining a mean-field approximation and a formula characterizing nonequlibrium steady states, which is obtained from the algebraic field approach to nonequlibrium statistical mechanics. When the bias voltage is chosen to be a control parameter, the phase transition between ordered and normal phases is found to be first or second order. Then, the voltage-current characteristics is S-shaped in some parameter region. In contrast, when the current is chosen to be a control parameter, all the non-trivial solutions of the self-consistent equation are found to become stable. In this case, the phase transition between the ordered and normal phases is always second order and negative differential conductivity appears at low temperature.

cond-mat.stat-mech↗

arXiv2008

Fluctuation theorem for currents in open quantum systems

A quantum-mechanical framework is set up to describe the full counting statistics of particles flowing between reservoirs in an open system under time-dependent driving. A symmetry relation is obtained which is the consequence of microreversibility for the probability of the nonequilibrium work and the transfer of particles and energy between the reservoirs. In some appropriate long-time limit, the symmetry relation leads to a steady-state quantum fluctuation theorem for the currents between the reservoirs. On this basis, relationships are deduced which extend the Onsager-Casimir reciprocity relations to the nonlinear response coefficients.

cond-mat.stat-mech↗

arXiv2006

Nonequilibrium Steady States and MacLennan-Zubarev Ensembles in a Quantum Junction System

Based on a recent progress in nonequilibrium statistical mechanics of infinitely extended quantum systems, a nonequlibrium steady state (NESS) is constructed for a single-level quantum dot interacting with two free reservoirs under less general but more practically useful conditions than the previous works. As an example, a model of an Ahoronov-Bohm ring with a quantum dot is studied in detail. Then, NESS is shown to be regarded as a MacLennan-Zubarev ensemble. A formal relation between response and correlation at NESS is derived as well.

cond-mat.other↗

arXiv2006

Note on MacLennan-Zubarev Ensembles and QuasiStatic Processes

Relation between natural nonequilibrium steady states of Ruelle and MacLennan-Zubarev ensembles is discussed for a system consisting of $M$ infinitely extended systems coupled with a small system. And a characterization of quasistatic processes is investigated for a small system coupled with a single reservoir.

math-ph↗

arXiv2006

Nonequilibrium Steady States and Fano-Kondo Resonances in an AB Ring with a Quantum Dot

Electron transport through a strongly correlated quantum dot (QD) embedded in an Aharonov-Bohm (AB) ring is investigated with the aid of the finite-U slave-boson mean-field (SBMF) approach extended to nonequilibrium regime. A nonequilibrium steady state (NESS) of the mean-field Hamiltonian is constructed with the aid of the C*-algebraic approach for studying infinitely extended systems. In the linear response regime, the Fano-Kondo resonances and AB oscillations of the conductance obtained from the SBMF approach are in good agreement with those from the numerical renormalization group technique (NRG) by Hofstetter et al. by using twice larger Coulomb interaction. At zero temperature and finite bias voltage, the resonance peaks of the differential conductance tend to split into two. At low bias voltage, the split of the asymmetric resonance can be observed as an increase of the conductance plateau. We also found that the differential conductance has zero-bias maximum or minimum depending on the background transmission via direct tunneling between the electrodes.

cond-mat.mes-hall↗

arXiv2005

Theoretical Study of Fano Resonance in Single-Walled Carbon Nanotubes

Electrical transport through single-walled carbon nanotubes (SWNTs) is investigated by using the nearest-neighbor tight-binding model coupled with two electron reservoirs. When the SWNT-electrode coupling is not axially symmetric, asymmetric resonance peaks are found in the conductance and are considered to be due to the interference between two transport channels. These Fano resonances are sensitive to the coupling with electrodes. When the coupling is axially symmetric, no asymmetric resonance peaks are observed.

cond-mat.mes-hall↗

arXiv2005

Reconnection of Stable/Unstable 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 stable/unstable manifolds of the Harper map. When the parameter changes to the reconnection threshold, the stable/unstable manifolds are shown to acquire new oscillatory portion corresponding to the heteroclinic tangle after the reconnection.

nlin.CD↗

arXiv2004

Nonlinear Transport and Current Fluctuation in an AB Ring with a Quantum Dot

Nonequilibrium steady states are explicitly constructed for a noninteracting electron model of an Aharonov-Bohm (AB) ring with a quantum dot (QD) with the aid of asymptotic fields. The Fano line shapes and AB oscillations are shown to strongly depend on the bias voltage. Current fluctuations are studied as well.

cond-mat.mes-hall↗

arXiv2004

Calculation of Correlation Functions in Terms of Fluctuation Relation

We derive a relation similar to the fluctuation theorem for work done on a system obeying Langevin dynamics with thermal and colored noises. Then, we propose a method of calculating the correlation function of the colored noise by using this fluctuation relation.

cond-mat.stat-mech↗

arXiv1998

An Analytical Construction of the SRB Measures for Baker-type Maps

For a class of dynamical systems, called the axiom-A systems, Sinai, Ruelle and Bowen showed the existence of an invariant measure (SRB measure) weakly attracting the temporal average of any initial distribution that is absolutely continuous with respect to the Lebesgue measure. Recently, the SRB measures were found to be related to the nonequilibrium stationary state distribution functions for thermostated or open systems. Inspite of the importance of these SRB measures, it is difficult to handle them analytically because they are often singular functions. In this article, for three kinds of Baker-type maps, the SRB measures are analytically constructed with the aid of a functional equation, which was proposed by de Rham in order to deal with a class of singular functions. We first briefly review the properties of singular functions including those of de Rham. Then, the Baker-type maps are described, one of which is non-conservative but time reversible, the second has a Cantor-like invariant set, and the third is a model of a simple chemical reaction $R \leftrightarrow I \leftrightarrow P$. For the second example, the cases with and without escape are considered. For the last example, we consider the reaction processes in a closed system and in an open system under a flux boundary condition. In all cases, we show that the evolution equation of the distribution functions partially integrated over the unstable direction is very similar to de Rham's functional equation and, employing this analogy, we explicitly construct the SRB measures.

chao-dyn↗