Micro mixer with fast diffusion

A concept for micromixing of liquid is introduced, and its feasibility is demonstrated. The mixer allows fast mixing of small amounts of two liquids and is applicable to microliquid handling systems. The mixer has a channel for the liquid, an inlet port for the reagent, a 2.2-mm×2-mm×330-μm mixing area, and 400 micronozzles (15 μm×15 μm) through with a reagent is injected into the sample liquid. The resulting microplumes greatly increase the contact surface between the two liquids and hasten the speed of the mixing by diffusion. The fabrication process is extremely simple. The mixing is complete within a few seconds; a homogeneous state of mixing is reached in 1.2 s when the total volume injected is 0.5 μl and the injection flow rate is 0.75 μl/

The effects of k-dependent self-energy in the electronic structure of correlated materials

It is known from self-energy calculations in the electron gas and sp materials based on the GW approximation that a typical quasiparticle renormalization factor (Z factor) is approximately 0.7-0.8. Band narrowing in electron gas at rs = 4 due to correlation effects, however, is only approximately 10%, significantly smaller than the Z factor would suggest. The band narrowing is determined by the frequency-dependent self-energy, giving the Z factor, and the momentum-dependent or nonlocal self-energy. The results for the electron gas point to a strong cancellation between the effects of frequency- and momentum-dependent self-energy. It is often assumed that for systems with a nar- row band the self-energy is local. In this work we show that even for narrow-band materials, such as SrVO3, the nonlocal self-energy is important.Comment: 7 pages, 6 figure

Proposal to look for an up/down asymmetry in atmospheric neutrinos beyond Multi-GeV region with existing experimental data

We discuss a possible test of neutrino oscillation hypothesis by proposing the combined analysis of high energy atmospheric neutrino induced muon events that have been detected around horizontal direction in the Kolar Gold Field (KGF) underground site and below the horizontal direction by many large detectors such as Super-Kamiokande and MACRO. Up/down asymmetry obtained using contained events recorded by detectors at Kamioka site probes low energy region of atmospheric neutrino whereas, the suggested method probes high energy neutrinos. It mainly depends on the observations and it is free of uncertainties in neutrino flux, interaction cross section etc. In this paper we demonstrate that the method is sensitive to a region of oscillation parameter space that explains all the features of atmospheric neutrino data in the Super-Kamiokande detector; the limiting factor being the statistical strength of the KGF observations. This method provides the only way to study the up/down asymmetry beyond Multi-GeV region which is yet to be measured experimentally.Comment: revtex, 6 pages with 3 eps figures. Error introduced by the different low-energy thresholds assessed, conclusion unchange

Weak and strong coupling limits of the two-dimensional Fr\"ohlich polaron with spin-orbit Rashba interaction

The continuous progress in fabricating low-dimensional systems with large spin-orbit couplings has reached a point in which nowadays materials may display spin-orbit splitting energies ranging from a few to hundreds of meV. This situation calls for a better understanding of the interplay between the spin-orbit coupling and other interactions ubiquitously present in solids, in particular when the spin-orbit splitting is comparable in magnitude with characteristic energy scales such as the Fermi energy and the phonon frequency. In this article, the two-dimensional Fr\"ohlich electron-phonon problem is reformulated by introducing the coupling to a spin-orbit Rashba potential, allowing for a description of the spin-orbit effects on the electron-phonon interaction. The ground state of the resulting Fr\"ohlich-Rashba polaron is studied in the weak and strong coupling limits of the electron-phonon interaction for arbitrary values of the spin-orbit splitting. The weak coupling case is studied within the Rayleigh-Schr\"odinger perturbation theory, while the strong-coupling electron-phonon regime is investigated by means of variational polaron wave functions in the adiabatic limit. It is found that, for both weak and strong coupling polarons, the ground state energy is systematically lowered by the spin-orbit interaction, indicating that the polaronic character is strengthened by the Rashba coupling. It is also shown that, consistently with the lowering of the ground state, the polaron effective mass is enhanced compared to the zero spin-orbit limit. Finally, it is argued that the crossover between weakly and strongly coupled polarons can be shifted by the spin-orbit interaction.Comment: 11 pages, 5 figure

Origin of Drastic Change of Fermi Surface and Transport Anomalies in CeRhIn5 under Pressure

The mechanism of drastic change of Fermi surfaces as well as transport anomalies near P=Pc=2.35 GPa in CeRhIn5 is explained theoretically. The key mechanism is pointed out to be the interplay of magnetic order and Ce-valence fluctuations. We show that the antiferromagnetic state with "small" Fermi surfaces changes to the paramagnetic state with "large" Fermi surfaces with huge enhancement of effective mass of electrons with keeping finite c-f hybridization. This explains the drastic change of the de Haas-van Alphen signals. Furthermore, it is also consistent with the emergence of T-linear resistivity simultaneous with the residual resistivity peak at P=Pc in CeRhIn5.Comment: 5 pages, 3 figures, submitted to Journal of Physical Society of Japa

Theory of Quasi-Universal Ratio of Seebeck Coefficient to Specific Heat in Zero-Temperature Limit in Correlated Metals

It is shown that the quasi-universal ratio $q=\lim_{T\to0}eS/C\sim\pm1$ of the Seebeck coefficient to the specific heat in the limit of T=0 observed in a series of strongly correlated metals can be understood on the basis of the Fermi liquid theory description. In deriving this result, it is crucial that a relevant scattering arises from impurities, but not from the mutual scattering of quasiparticles. The systematics of the sign of $q$ is shown to reflect the sign of the logarithmic derivative of the density of states and the inverse mass tensor of the quasiparticles, explaining the systematics of experiments. In particular, the positive sign of $q$ for Ce-based and $f^{3}$-based heavy fermions, and the negative sign for Yb-based and $f^{2}$-based heavy fermions, are explained. The case of non-Fermi liquid near the quantum critical point (QCP) is briefly mentioned, showing that the ratio $q$ decreases considerably toward antiferromagnetic QCP while it remains essentially unchanged for the ferromagnetic QCP or QCP due to a local criticality.Comment: 12 pages, 1 figur

Realization of odd-frequency p-wave spin-singlet superconductivity coexisting with antiferromagnetic order near quantum critical point

A possibility of the realization of the p-wave spin-singlet superconductivity ($p$SS), whose gap function is odd both in momentum and in frequency, is investigated by solving the gap equation with the phenomenological interaction mediated by the antiferromagnetic spin fluctuation. The $p$SS is realized prevailing over the d-wave singlet superconductivity ($d$SS) in the vicinity of antiferromagnetic quantum critical pint (QCP) both on the paramagnetic and on the antiferromagnetic sides. Off the QCP in the paramagnetic phase, however, the $d$SS with line-nodes is realized as \textit{conventional} anisotropic superconductivity. For the present $p$SS state, there is no gap in the quasiparticle spectrum everywhere on the Fermi surface due to its odd frequency. These features can give a qualitative understanding of the anomalous behaviors of NQR relaxation rate on CeCu$_2$Si$_2$ or CeRhIn$_5$ where the antiferromagnetism and superconductivity coexist on a microscopic level.Comment: 20 pages with 12 figures. To appear in J. Phys. Soc. Jpn. Vol. 72, No. 1