618 research outputs found
Field-Enhanced Kondo Correlations in a Half-Filling Nanotube Dot: Evolution of an SU(N) Fermi-Liquid Fixed Point
We theoretically study an emergent SU(2) symmetry which is suggested by
recent magneto-transport measurements, carried out near two electrons filling
of a carbon nanotube quantum dot. It emerges in the case where the spin and
orbital Zeeman splittings cancel each other out for two of the one-particle dot
levels among four. Using the Wilson numerical renormalization group, we show
that a crossover from the SU(4) to SU(2) Fermi-liquid behavior occurs at two
impurity-electrons filling as magnetic field increases. We also find that the
quasiparticles are significantly renormalized as the remaining two one-particle
levels move away from the Fermi level and are frozen at high magnetic fields.
In order to clarify how the ground state evolves during such a crossover, we
also reexamine the SU(N) Kondo singlet state for M impurity-electrons filling
in the limit of strong exchange interactions. We show that the nondegenerate
Fermi-liquid fixed point of Nozi\`{e}es and Blandin can be described as a
bosonic Perron-Frobenius vector for M hard-core bosons, each of which consists
of one impurity-electron and one conduction hole. This interpretation can also
be applied to the Fermi-liquid fixed-point without the SU(N) symmetry.Comment: 20 pages, 10 figures, Sec.III B. has been revised. J.Phys.Soc.Jpn.in
pres
Vertically stacked graphene tunnel junction with structured water barrier
We report a vertically stacked graphene tunnel junction with an atomically thin insulating layer for novel function devices. The insulating water layer sandwiched between graphene samples as a tunnel barrier which is fabricated through deionized (DI) water treatment of epitaxial graphene. Two graphene samples fabricated by SiC thermal decomposition are directly bonded to each other in a face-to-face manner. Vertically stacked graphene samples without DI water treated formed an ohmic junction. By inserting the structured water layer as tunnel barrier, the stacked junction exhibits Direct tunneling (DT) characteristics in a low-electric-field regime and Fowler-Nordheim tunneling (FNT) characteristics in a high-electric-field regime. The thickness of the structured water layer is estimated to be 0.28 nm by fitting the FNT formula. The very thin structured water layer is stable as tunnel barrier on epitaxial graphene for diode devices, which will have a widely application in electronic devices
Graduation Thesis Activity at Miharashidai Gakuen College: Considering the Method of Learning Support for Facilitating the Learning of Young People with Developmental and Intellectual Disabilities at Universities
departmental bulletin pape
Applications of Student’s Learning in the Area of “Musical Expression” through Active Learning: “Making a Musical Drama Together” for Children Who Have Special Needs in Developmental Center Z
departmental bulletin pape
- …