Noriyuki Hatakenaka

Crystal topology: A Möbius strip of single crystals

A Möbius strip is produced by twisting a ribbon of material through 180° and joining its two ends, resulting in a distinct, one-sided topology. Here we describe a Möbius structure formed by crystals of a compound of niobium and selenium, NbSe3. It is surprising that a crystalline ribbon should adopt this exotic topology in view of its inherent rigidity, which would be expected to prevent it from either bending or twisting.

QUANTUM-CIRCUIT ANALOG OF THE DYNAMICAL CASIMIR EFFECT AT FINITE TEMPERATURES

We proposed a quantum-circuit analog of dynamical Casimir effect by using a superconducting quantum circuit. The proposed system can be regarded as a time-dependent harmonic oscillator, resulting in squeezing of a quantum flux trapped in the system. Here we develop our theory taking into account finite temperatures, in order to contact with experiments like circuit-QED. We present numerical results of occupation probability distributions produced by non-stationary boundary effect at various temperatures.

Anomalous Switching-Current Distributions to the Voltage State in a Small Josephson Junction

Switching-current distribution for supercurrent-state decay is investigated in small Josephson junctions at zero temperature. Due to resonant features of the tunneling process reflecting the existence of quantized energy levels in Josephson potential, decay to the voltage state is enhanced or suppressed by changing bias current. As a result, the switching-current distribution has peculiar peaks in a low bias regime. Resonant processes are also controlled by the sweep rate of the junction.