Atsunobu Nakamura

WAVE FUNCTIONS AROUND THE INJECTOR OF THE TWO-DIMENSIONAL ELECTRON SYSTEM

We calculate the wave functions of the stationary states for the geometry of the semi-infinite two-dimensional region with a narrow channel as a first step in the investigation of the behaviour of the electron waves around the injector. In the presence of a magnetic field, we obtain a periodic peak structure in the modulus squared of the wave function along the boundary in the semi-infinite two-dimensional region, the period of which is nearly equal to the classical cyclotron diameter. Moreover, it is shown that small peaks exist between the periodic main peaks, which is considered to be one of the characteristic aspects of the quantum interference effects.

Spin excitations of a ferromagnetic wire with a magnetic domain wall

Abstract The spin excitation for a ferromagnetic wire with a domain wall (DW) is studied in a framework of the random phase approximation. We show that the excitation energy due to the DW is much smaller than that for the spin wave. In the spin-wave spectrum, there are lots of peaks or shoulders, which is related to the existence of the DW and the dimension of the leads. Using the results, the energy dissipation of conduction electrons is also discussed.

Behaviour of an Electron Wave in Electron-Focusing Geometry

In electron-focusing geometry in the presence of a magnetic field, numerical calculations have been made for the wave functions of stationary states and for transmission probability of the electron wave from the injector to the collector. The pattern behaviour of transmission probability is demonstrated as a function of the external magnetic field. The results obtained here reproduce the experimental focusing spectra qualitatively.

QUANTUM INTERFERENCE EFFECTS OF ELECTRONS SCATTERED BY ANTIDOTS IN MAGNETIC FIELDS

Abstract We investigate the quantum transport phenomena for a quasi-one-dimensional quantum wire with antidots in magnetic fields. The calculated magnetoconductance shows a quasi-periodic structure of the group of dips. The characteristic properties of the magnetoconductance can be understood through a simple hopping model, where the electron transfers between the neighboring pinned orbits. We also discuss the interference effects on the conductance in connection with local electronic states.

ELECTRON SCATTERING BY A RING-SHAPED BARRIER IN MAGNETIC FIELDS

Abstract We investigate the transport phenomena through a region containing a ring-shaped barrier in a quasi-one-dimensional quantum wire in magnetic fields. The calculated magnetoconductance curve shows a periodic dip structure, which is superimposed upon by another quasi-periodic dip structure. The current distributions for resonant states and the magnetoconductance features are well explained on the basis of the magnetic field dependence of the eigenvalue in the two-dimensional system.

Hartree-Fock treatment for the electron states in the quantum wire

We calculate the spatial distribution of the electron density and the dispersion curves of the subband structure for the quantum wire patterned from the GaAs/AlGaAs heterostructure within the framework of the Hartree-Fock approximation. It is shown that electrons move to the part underneath the modulation-doped layer as the strength of the Coulomb interaction is increased, and that the pattern behaviour of the dispersion curve below the Fermi energy depends strongly on the strength of the Coulomb interaction and on the total electron number.

Crystal-Field Effects on Thermoelectric Power and Resistivity for the Ce-Kondo System

The thermoelectric power and the resistivity for the Ce-Kondo system are precisely calculated at low temperatures. The local Fermi liquid theory is extended to the case including the crystalline field in order to precisely evaluate the thermoelectric power with the aid of the Bethe Ansatz method. The characteristic properties caused by the crystal-field effects are investigated for the above quantities. The anisotropic properties are discussed briefly for the hexagonal and tetragonal fields.

Thermal conductivity and Lorenz number of the heavy electron in Ce compounds

Abstract The thermal conductivity and the Lorenz number are investigated using the Anderson lattice model in the framework of the single-site approximation. The obtained results are qualitatively in agreement with the experimental findings of CeAl 3 . The characteristic features of the transport properties in the presence of a magnetic field are also discussed in connection with the gap structure above the Fermi level.

Crystal-field effects on low-frequency susceptibility for Ce-Kondo system

The low-frequency dynamical susceptibility for the Ce-Kondo system is investigated on the basis of the local Fermi liquid theory at zero temperature. The effects of the crystalline field are studied precisely by means of the Bethe-Ansatz solution of the Anderson model, for the cases of cubic, hexagonal and tetragonal fields. It is shown that the magnetic relaxation rate of the f -electron is enhanced in general in the presence of the crystalline fields. The anisotropic properties of the relaxation are discussed for hexagonal and tetragonal fields as well.

Magnetic field dependence of spin-flip cross section for polarized neutron scattering of CeCu2Si2

The magnetic field dependence of the spin-flip cross section for quasielastic polarized neutron scattering is investigated for the Ce Kondo system at zero temperature. An exact calculation is done for the differential cross section with a small energy transfer and also for the total cross section. In particular the latter case is discussed in detail in order to investigate the recent experiment done for the polycrystalline CeCu2Si2. With the use of the obtained results, two possibilities are discussed about the wavefunction for the crystal-field ground doublet of the f-electron in CeCu2Si2.