Masayuki Hashisaka

Multiferroic thin film of Bi2NiMnO6 with ordered double-perovskite structure

Epitaxial thin films of Bi2NiMnO6 were synthesized on SrTiO3 substrates by pulsed laser deposition. The resulting film had the rock-salt-type arrangement of Ni2+ and Mn4+ ions in a double-perovskite unit cell. The films clearly showed multiferroic properties, both ferromagnetic behavior with a Curie temperature of about 100K and ferroelectric behavior with a saturated polarization of about 5μC∕cm2.

Epitaxial growth of ferromagnetic La2NiMnO6 with ordered double-perovskite structure

Epitaxial thin films of ordered double-perovskite La2NiMnO6 were deposited on SrTiO3, (LaAlO3)0.3–(Sr2AlTaO6)0.7, and LaAlO3 substrates by a pulsed-laser deposition method. A rock-salt-type ordering for Ni2+ and Mn4+ ions was confirmed through structural and magnetic measurements. Despite the difference in heteroepitaxial constraints on the crystal structure, the magnetic properties of the films were quite similar to each other and also to those of bulk La2NiMnO6.

Nonequilibrium fluctuation relations in a quantum coherent conductor

We experimentally demonstrate the validity of nonequilibrium fluctuation relations by using a quantum coherent conductor. In equilibrium the fluctuation-dissipation relation leads to the correlation between current and current noise at the conductor, namely, the Johnson-Nyquist relation. When the conductor is voltage biased so that the nonlinear regime is entered, the fluctuation theorem has predicted similar nonequilibrium fluctuation relations, which hold true even when the Onsager-Casmir relations are broken in magnetic fields. Our experiments qualitatively validate the predictions as the first evidence of this theorem in the nonequilibrium quantum regime.

Fluctuation theorem and microreversibility in a quantum coherent conductor

Mesoscopic systems provide us a unique experimental stage to address nonequilibrium quantum statistical physics. By using a simple tunneling model, we describe the electron exchange process via a quantum coherent conductor between two reservoirs, which yields the fluctuation theorem (FT) in mesoscopic transport. We experimentally show that such a treatment is semiquantitatively validated in the current and noise measurement in an Aharonov-Bohm ring. The experimental proof of the microreversibility assumed in the derivation of FT is presented.

Measurement for quantum shot noise in a quantum point contact at low temperatures

We report an experimental development for the high-frequency shot noise measurement system in the 3He-4He dilution refrigerator. The target frequency of the measurement was set to a few MHz with the cross correlation scheme adopted for high accuracy. The system was calibrated by measuring Johnson-Nyquist noise of the quantum point contact (QPC). We prove that our system has enough accuracy for the quantitative evaluation of the quantum shot noise.

Conductance Anomaly and Fano Factor Reduction in Quantum Point Contacts

We report an experimental study on the shot noise as well as the dc transport properties of a quantum point contact (QPC) whose conductance anomaly can be tuned electrostatically by the gate electrodes. By controlling the single QPC so that it has no anomaly or an anomaly at 0.5, 0.8 or

Bolometric detection of quantum shot noise in coupled mesoscopic systems

0.9{G}_{0}

Universality of bias- and temperature-induced dephasing in ballistic electronic interferometers

({G}_{0}=2{e}^{2}/h)

Temperature dependence of the visibility in an electronic Mach–Zehnder interferometer

, we prove that the anomaly always accompanies the Fano factor reduction due to the asymmetric transmission of the two spin-dependent channels for the conductance lower than