Naoki Tokuda

Quantized thermoelectric power in the ballistic transport regime

The thermoelectric power of a narrow constriction in a two-dimensional electron gas (2DEG) is theoretically investigated in the form of the transverse voltage by using a model appropriate for the recent experimental system. Our theoretical model gives the quantized thermoelectric power obtained experimentally. Moreover, the oscillating chemical potentials in all the participating 2DEG regions are found.

Transitions of the ground state and electron-electron correlations in barrier centres in magnetic fields

The relation between the electron-electron correlations and magnetic-field-induced angular momentum transitions in the barrier centre is investigated based on a variational method. The Chandrasekhar-type variational wavefunctions for the barrier states are constructed based on the exact solutions in the strong-magnetic-field limit. The energies of the barrier states, the binding energies, the electron densities, the angular correlations, and the average distances between the two electrons are obtained as functions of the applied magnetic field strength and the distance between the positive ion and the plane where the two electrons reside. When the transitions of the barrier ground state occur for finite with increasing , the strong correlations appear in the electron densities, the angular correlations, and the average distances between the two electrons. As a consequence of detailed considerations of the relation between the angular correlations and the strength of binding, we find that the magnetic-field-induced angular-momentum transitions occur as a result of the strong correlations in the barrier states.

Quantized thermoelectric power and oscillating chemical potential in the ballistic transport regime

The thermoelectric power of a narrow constriction in a two-dimensional electron gas (2DEG) in AlxGa1-xAs/GaAs heterojunctions is theoretically investigated in the form of the transverse voltage by using an appropriate model for the recent experimental system. The model gives not only the quantized thermoelectric power obtained theoretically and experimentally but also the oscillating chemical potentials in all the participating 2DEG regions. The temperature dependence of the transverse voltage is also studied focusing on the effect of the thermal broadening of the electron distribution functions.

Surface bipolaron formation in the two-electron-plus-ripplon system

Abstract Using a variational method of the Pekar type, we examine the formation of surface bipolaron by coupling of two electrons to ripplons, the symmetry property of the system being taken into account. It is found that the surface bipolarons with an odd as well as an even parity can exist as the ground state for certain ranges of the electron-ripplon coupling constant and the strength of the Coulomb repulsion.

C, P and T Invariances and the Bootstrap Hypothesis

It is investigated whether the charge conjugation, space reflection and time reversal invariances in the strong interactions can be understood in the framework of the bootstrap dynamics, within a limited model of the pion-nucleon system. It is found that not only the above mentioned invariances but also the charge independence can be attributed to the dynamical self-consistency :requirements on the pion-nucleon vertex and on the self-energies of the various particles.

On the Yang-Treiman Asymmetry and the Nucleon Isobar

Relativistic perturbation theory was used to calculate the contribution of nucleon isobar formation in a previously reported deviation from the one-pion- exchange mechanism on the pi - pi scattering angular distributions in the reaction pi- + p carbon materia pi+ + pi- + n at very low momentum transfer. It was found that the contribution of the nucleon isobar could not account for the large asymmetry reported. (C.E.S.)

A SOLUBLE MODEL OF THE PARTIAL WAVE DISPERSION EQUATION AND THE BOOTSTRAP APPROXIMATION

An exactly soluble model of a p-wave dispersion equation is investigated to see the validity of the bootstrap approximation. The model contains a parameter which is related to the coupling constant of the corresponding field theoretical model, the meson pair theory with a generalized separable interaction potential. For a certain range of the parameter, the model exhibits a resonance of positive width and the bootstrap equation can be constructed for the resonance. Its equation can be solved numerically, which gives the position and the reduced width of the resonance as the functions of the parameter. The results are compared with the exact one and the validity of the bootstrap approximation is discussed in detail. (auth)