Excess Entropy Production in Quantum System: Quantum Master Equation Approach

For open systems described by the quantum master equation (QME), we investigate the excess entropy production under quasistatic operations between nonequilibrium steady states. The average entropy production is composed of the time integral of the instantaneous steady entropy production rate and the excess entropy production. We propose to define average entropy production rate using the average energy and particle currents, which are calculated by using the full counting statistics with QME. The excess entropy production is given by a line integral in the control parameter space and its integrand is called the Berry–Sinitsyn–Nemenman (BSN) vector. In the weakly nonequilibrium regime, we show that BSN vector is described by \(\ln \breve{\rho }_0\) and \(\rho _0\) where \(\rho _0\) is the instantaneous steady state of the QME and \(\breve{\rho }_0\) is that of the QME which is given by reversing the sign of the Lamb shift term. If the system Hamiltonian is non-degenerate or the Lamb shift term is negligible, the excess entropy production approximately reduces to the difference between the von Neumann entropies of the system. Additionally, we point out that the expression of the entropy production obtained in the classical Markov jump process is different from our result and show that these are approximately equivalent only in the weakly nonequilibrium regime.     

Lorenz number determination of the dissipationless nature of the anomalous Hall effect in itinerant ferromagnets

We have measured the thermal Hall conductivity for ferromagnetic Ni and Ni0.97Cu0.03. In the low temperature region ( less, similar 100 K), we show for the first time that the Wiedemann-Franz law is satisfied even for the anomalous Hall current. While the Hall Lorenz number for the normal part decreases rapidly with temperature, that for the anomalous part shows much less deviation from the free-electron Lorenz number. This evidences the dissipationless nature of the anomalous Hall effect.     

Correlation between spin helicity and an electric polarization vector in quantum-spin chain magnet LiCu2O2

Measurements of polarized neutron scattering were performed on a S=1/2 chain multiferroic LiCu2O2. In the ferroelectric ground state with the spontaneous polarization along the c axis, the existence of transverse spiral spin component in the bc plane was confirmed. When the direction of electric polarization is reversed, the vector spin chirality as defined by C_(ij)=S_(i)xS_(j) (i and j being the neighboring spin sites) is observed to be reversed, indicating that the spin-current model or the inverse Dzyaloshinskii-Moriya mechanism is applicable even to this e_(g)-electron quantum-spin system. Differential scattering intensity of polarized neutrons shows a large discrepancy from that expected for the classical-spin bc-cycloidal structure, implying the effect of large quantum fluctuation.     

Multicritical end point of the first-order ferromagnetic transition in colossal magnetoresistive manganites

We have studied the bandwidth-temperature-magnetic-field phase diagram of RE0.55Sr0.45MnO3 colossal magnetoresistance manganites with ferromagnetic metal (FM) ground state. The bandwidth was controlled both via chemical substitution and hydrostatic pressure with a focus on the vicinity of the critical pressure p;{*} where the character of the zero-field FM transition changes from first to second order. Below p;{*} the first-order FM transition extends up to a critical magnetic field. It approaches zero on the larger bandwidth side where the surface of the first-order FM phase boundary is terminated by a multicritical end point. The change in the character of the transition and the decrease of the colossal magnetoresistance effect is attributed to the reduced charge-order and orbital-order fluctuations.     

Evidence for an electric-dipole active continuum band of spin excitations in multiferroic TbMnO3

The wide range optical spectra on a multiferroic prototype TbMnO3 have been investigated to clarify the origin of spin excitations observed in the far-infrared region. We elucidate the full band structure, whose high energy edge (133 cm;{-1}) exactly corresponds to twice of the highest-lying magnon energy. Thus the origin of this absorption band is clearly assigned to two-magnon excitation driven by the electric field of light. There is an overlap between the two-magnon and phonon energy ranges, where the strong coupling between them is manifested by the frequency shift and transfer of oscillator strength of the phonon mode.     

Direct filature of bacterial cellulose from culture medium

The continuous Filature of bacterial cellulose has been achieved directly from culture medium using shallow culture pan newly designed. A remarkable progress of fiber properties was observed comparing with regenerated cellulosic filaments on the filament of bacterial cellulose dependently on the rinsing process with water or ethylene glycol. The progress of fiber properties was also shown on the filament of N-acetylglucosamine(GlcNAc) incorporated bacterial cellulose probably due to enforcement of fiber interactions. A copolymer of carboxymethylglucose (CM-Glc) and glucose has been achieved successfully to increase the adsorption capacity for lead ion comparing with original carboxymethyl cellulose (CMC).     

Colossal magnetoresistive manganites

Magnetoelectronic features of the perovskite-type manganites are overviewed in the light of the mechanism of the colossal magnetoresistance (CMR). The essential ingredient of the CMR physics is not only the double-exchange interaction but also other competing interactions, such as ferromagnetic/antiferromagnetic superexchange interactions and charge/orbital ordering instabilities as well as their strong coupling with the lattice deformation. In particular, the orbital degree of freedom of the conduction electrons in the near-degenerate 3d e_g state plays an essential role in producing the unconventional metal–insulator phenomena in the manganites via strong coupling with spin, charge, and lattice degrees of freedom. Insulating or poorly conducting states arise from the long or short-range correlations of charge and orbital, but can be mostly melted or turned into the orbital-disordered conducting state by application of a magnetic field, producing the CMR or the insulator–metal transition.     

Platelet aggregation inhibitors from Populus sieboldii Miquel.

The water extract of Populus sieboldii Miquel (Salicaceae) inhibited arachidonic acid-induced platelet aggregation. Pyrocatechol and salicyl alcohol were isolated as active constituents. Pyrocatechol showed an inhibitory effect on platelet aggregation induced by arachidonic acid with IC100 value of 4 microM, which was 25 times more potent than aspirin.