Norio Inui

Abstract The temporal variation of the electric current induced by an oscillating Peierls phase in a ring-shaped system is studied using a tight-binding model with the Peierls substitution. For a single electron current, when the initial wavefunction is a traveling wave with a constant wave number, the time-averaged current does not depend on the oscillation frequency of Peierls phase, in contrast to conventional electrical induction. However, when the initial state is a superposition of degenerate eigenstates, the mean square current between nearest-neighbor sites depends on both the initial amplitudes of the clockwise and counterclockwise traveling waves and the oscillation frequency. Moreover, the total current, defined as the sum of currents between nearest-neighbor sites and determines the induced magnetic field, depends on the amplitudes of the superposition but remains independent of the oscillation frequency.

Abstract The time-averaged orbital angular momentum of an oscillator coupled to single- and dual-frequency electromagnetic waves is investigated by exactly solving the Heisenberg equation of motion. An applied magnetic field splits the natural frequency of the oscillator into distinct resonances in the presence of a single-frequency wave. When the magnetic interaction is much stronger than the dipole interaction, the angular momentum reaches extreme values near the lower and upper split frequencies. For dual frequencies, if the two frequencies are widely separated, the angular momentum is approximately a superposition of the single-frequency cases. Consequently, the total angular momentum is represented as the sum of contributions from the lower and higher frequencies in strong magnetic fields. However, significant deviations from this superposition occur when the oscillator interacts with closely spaced frequencies.

Abstract Temporal variations in electric currents along a ring, induced by a time-dependent magnetic flux are examined using the tight-binding model. When all nearest-neighbor atom pairs share the same transfer integral and the Peierls phase changes linearly with time, the resulting electric current remains uniform and matches the magnitude of the current induced by a static magnetic field producing the same Peierls phase. However, in the presence of disorder, where transfer integrals differ, the electric current becomes position-dependent. For a randomly disordered ring with the transfer integrals following a normal distribution, an increase in the standard deviation reduces the mean electric current under a static magnetic field. In contrast, when exposed to a time-varying magnetic field, the induced currents in the disordered ring can increase as the standard deviation increases.

Abstract The induction of electric current between atoms arranged in concentric circles by an external magnetic field is studied using a tight-binding model. In particular, the dependence of electric current on the strength of the magnetic field, number of atoms, and temperature is examined. Substantial changes are observed in the electric current distribution when the difference in the transfer integral along the circumference and between circles is increased. Additionally, the difference in the electric current flow compared with that through a graphene ring is analyzed.

Abstract The magnetic properties of a circular graphene nanoribbon (carbon belt) in a magnetic field parallel to its central axis is studied using a tight-binding model. Orbital magnetic susceptibility is calculated using an analytical expression of the energy eigenvalues as a function of the magnetic flux density for any size, and its temperature dependence is considered. In the absence of electron hopping parallel to the magnetic field, the orbital magnetic susceptibility diverges at absolute zero if the chemical potential is zero and the number of atoms is a multiple of four. As the temperature increases, the magnitude of susceptibility decreases according to the power law, whose exponent depends on the size. In the presence of electron hopping parallel to the magnetic field, the divergence of the susceptibility near absolute zero disappears, and the sign changes with the transfer integral parallel to the magnetic field and the temperature.

構成原子数が数千個であるArクラスターイオンを金属に衝突させた結果、その衝撃により構成原子数がより少ないクラスターイオンに解離した。この解離特性が、クラスターイオンと金属の接触面に作用する衝撃応力と相関関係があることを見出した。今回の報告では、ターゲットとして異なる種類の金属、および金属にグラフェンを積層させた場合について検討したところ、興味深い知見が得られたので報告する。