Research summary 2010
We study prominent quantum phenomena in condensed matter in a wide
temperature range including micro Kelvin region. We carried out the
experiment on surface phenomena of superfluid 3He. Supersolid
properties in solid He is studied under rotation. Millimeter wave
absorption induced resistance of surface state electrons on liquid He
is studied under magnetic fields, where diminishing resistance is
observed. Coherent nuclear spin manipulation is achieved in vertical
double quantum dots by means of electric potential and RF pulse.
Spatial distribution of dynamical nuclear spin polarization is studied
in the quantum Hall effect breakdown regime. Quantum transport
measurement is done under ultralow temperature environment.
Surface phenomena on quantum systems
Transport properties of 2D electrons on liquid He under millimeter
wave irradiation (D. Konstantinov, K. Kono)
The excitation of surface state electrons by irradiating 100GHz range
millimeter wave induces a prominent transport effect. Under strong
magnetic fields the resistance exhibited novel magneto-oscillations
and the resistance eventually shows zero resistance states.
Transport properties of ion pools under a free surface of superfluid
3He (T. Matsumoto, H. Ikegami, K. Kono)
Aiming the detection of surface bound states in the vicinity of free
surface of superfluid 3He, we have measured the conductivity of ion
pools below the surface.
Transport properties of point-contact in electrons on liquid He
(D. Ress, K. Kuroda, M. Hoefer, P. Leiderer, K. Kono)
By employing nanogapped electrodes and capillary-condensed He
channels, a point-contact device is fabricated. The point-contact
device shows step-like I-V characteristics, which are ascribed to the
granularity of electrons and charging energy.
Study of supersolid He under rotation (H. Choi, E. Kim, D. Takahashi,
Torsional oscillator response of solid helium is studied under
rotation together with rigidity. The result is naturally interpreted
by a supersolid model.
Spectroscopy of Ba ions under a free surface of liquid He
(M. Watanabe, M. Schmotz, R. Batulin, K. Kono)
In order to study Majorana nature of surface bound states under a free
surface of superfluid 3He, spectroscopy of Ba ion is developed. This
year a laser aberration is tried to produce Ba ions in liquid He.
Low temperature quantum transport in nano structures
Nuclear spin effect in semiconductor quantum dots (R. Takahashi,
K. Ono, K. Kono)
Coherent and bi-directional nuclear spin manipulation is demonstrated
in vertical double quantum dots. Application of electric potential and
rf-NMR pulses achieve an arbitrary polarization of coherent
nuclear. This will be used in a technology of quantum memory.
Manipulation of three spins in double quantum dot(S. Amaha, K. Ono,
Novel spin blockade for three electron spins are found in double
quantum dots. This will be used for initializing multi spin qubits.
Breakdown of quantum Hall effect and nuclear spin polarization
(M. Kawamura, and K. Kono)
We have studied dynamical nuclear spin polarization induced by the
breakdown of quantum Hall effect. We conducted experiments using
multi-terminal Hall-bar devices and found that the amplitudes of
nuclear magnetic resonance signals from the polarized nuclear spins
depend on the distance from the electron-injecting electrode. This
result directly shows that the dynamic nuclear spin polarization has a
spatial gradient in the device. The spatial gradient is explained by
the avalanche-type breakdown mechanism of the quantum Hall effect
Ultra-low temperature measurement of semiconductor quantum dot
transport properties (A. Badrutdinov, SM. Huang, H. Akimoto, K. Ono,
H. Ikegami, H. Ishimoto, K. Kono)
Spin blockade and nuclear spin effects are studied down to sub-mili
Kelvin temperature. An enhancement of nuclear spin decay time is