Research summary 2005
We study prominent quantum phenomena in condensed matter in a wide
temperature range including micro Kelvin region. Ultra-low
tempearture facility is established and we started the experiment on
2D electrons on superfluid 3He. Rotating cryostat starts
working. Millimeter wave absorption because of transitions between
electronic surface states on liquid He is observed. In order to
fabricate vertical quantum dots based on GaAs semiconductor, we
introduced ECR dry-etching equipment. The quantum dots may be used
for quantum information processing.
Surface phenomena on quantum systems
The resistivity measurement of the Wigner solid on supeerfluid
3He under a magnetic field is carried out. The observation
on A-pahse shows a clear evidence for gap nodes.
On a rotating cryostat, the mobility of 2D electrons on rotating
superfluid is measured. Magnetoresistance shows a prominent rotation
To control and detect single electrons on liquid He surface and to
develop quantum computing, the excitation of surface state electrons
by irradiating 130GHz millimeter wave is tried. Absorption of
millimeter wave is observed and temperature dependence of linewidth
and shape is studied.
Transport of 2D electrons on a thin helium film is studied. Capillary
condensed quasi-one-dimensional channel is used to meaure the
conductivity of electrons supported by the channel.
Low temperature quantum transport in nano structures
An ECR dry-etching equipment is introduced and the performance was
tuned in order to fabricate a GaAs based quantum dots.
Mesoscopic Hall probe made from GaAs heterostructure is improved to
detect the spatial distribution of flux quanta in mesoscopic
Quantum transport of atomic contact controlled by a
mechanical-break-junction technique is carried out at dilution
temperatures. Superconducting properties of an atomic contact is
studied in Al. A break junction of organic conductor is made and
conductance quatization at a half-integer is observed.
A prominent single electron charging effect, or Coulomb diamond was
observed at 4K in single gold particle of 10 nanometer in diameter. A
nolinear behaviour is attributed to the transport peculiality of
New organic TFTs are developed by the use of nano-fabrication