Singlet and Triplet Superfluid Competition in a Mixture of Two-Component Fermi and One-Component Dipolar Bose Gases

We consider a mixture of two-component Fermi and (one-component) dipolar Bose gases in which both dipolar interaction and s-wave scattering between fermions of opposite spins are tunable. We show that in the long wavelength limit, the anisotropy in the Fermi-Fermi interaction induced by phonons of the dipolar condensate can strongly enhance the scattering in the triplet channel. We investigate in detail the conditions for achieving optimal critical temperature at which the triplet superfluid begins to compete with the singlet superfluid.Comment: 5 pages, 2 figure

Modeling Mobility Degradation in Scanning Capacitance Microscopy for Semiconductor Dopant Profile Measurement

Scanning capacitance microscopy (SCM) based on the MOS capacitor C-V characteristics is a comparative new technique for dopant profile extraction. It utilises the high spatial resolution of scanning probe microscopy. However extraction of dopant profile near a p-n junction has not been successful due to the complex physics involved: typically unrealistically high dopant concentration near the junction is deduced (corresponding to low SCM dC/dV data). Better understanding of SCM measurement and modelling is required to enhance the accuracy of the extracted dopant concentration. This paper addresses the influence of mobility degradation on the SCM measurement via modelling and comparison with experimental SCM data. The rational for looking into mobility effect is that SCM capacitance measurement is carried out at 915 MHz. At this frequency, resistance of semiconductor surface can be comparable to the reactance of the SCM capacitance. In our simulation carrier mobilities at the semiconductor surface are set low compared to their bulk values to reflect surface mobility degradation. Our results show that the simulated SCM dC/dV is significantly reduced in the vicinity of p-n junction reflecting what is observed experimentally. We attribute this to the fact that the capacitance between the inverted surface and the SCM probe is not detected due to the high resistance (compared to the reactance of the SCM capacitance) of the inversion layer below the semiconductor and oxide interface. Only the capacitance on the accumulation side is extracted thus leading to the lowering of the detected SCM capacitance and dC/dV. The major conclusion is that the effect of high resistance due to mobility degradation has to be treated carefully for accurate extraction of dopant profile from experimental SCM data

Modeling the Effects of Interface Traps on Scanning Capacitance Microscopy dC/dV Measurement

Scanning capacitance microscopy (SCM) measurement is a proposed tool for dopant profile extraction for semiconductor material. The influence of interface traps on SCM dC/dV data is still unclear. In this paper we report on the simulation work used to study the nature of SCM dC/dV data in the presence of interface traps. A technique to correctly simulate dC/dV of SCM measurement is then presented based on our justification. We also analyze how charge of interface traps surrounding SCM probe would affect SCM dC/dV due the small SCM probe dimension

Spontaneous phase oscillation induced by inertia and time delay

We consider a system of coupled oscillators with finite inertia and time-delayed interaction, and investigate the interplay between inertia and delay both analytically and numerically. The phase velocity of the system is examined; revealed in numerical simulations is emergence of spontaneous phase oscillation without external driving, which turns out to be in good agreement with analytical results derived in the strong-coupling limit. Such self-oscillation is found to suppress synchronization and its frequency is observed to decrease with inertia and delay. We obtain the phase diagram, which displays oscillatory and stationary phases in the appropriate regions of the parameters.Comment: 5 pages, 6 figures, to pe published in PR

Exact solution of gyration radius of individual's trajectory for a simplified human mobility model

Gyration radius of individual's trajectory plays a key role in quantifying human mobility patterns. Of particular interests, empirical analyses suggest that the growth of gyration radius is slow versus time except the very early stage and may eventually arrive to a steady value. However, up to now, the underlying mechanism leading to such a possibly steady value has not been well understood. In this Letter, we propose a simplified human mobility model to simulate individual's daily travel with three sequential activities: commuting to workplace, going to do leisure activities and returning home. With the assumption that individual has constant travel speed and inferior limit of time at home and work, we prove that the daily moving area of an individual is an ellipse, and finally get an exact solution of the gyration radius. The analytical solution well captures the empirical observation reported in [M. C. Gonz`alez et al., Nature, 453 (2008) 779]. We also find that, in spite of the heterogeneous displacement distribution in the population level, individuals in our model have characteristic displacements, indicating a completely different mechanism to the one proposed by Song et al. [Nat. Phys. 6 (2010) 818].Comment: 4 pages, 4 figure

Superfluid pairing in a mixture of a spin-polarized Fermi gas and a dipolar condensate

We consider a mixture of a spin-polarized Fermi gas and a dipolar Bose-Einstein condensate in which s-wave scattering between fermions and the quasiparticles of the dipolar condensate can result in an effective attractive Fermi-Fermi interaction anisotropic in nature and tunable by the dipolar interaction. We show that such an interaction can significantly increase the prospect of realizing a superfluid with a gap parameter characterized with a coherent superposition of all odd partial waves. We formulate, in the spirit of the Hartree-Fock-Bogoliubov mean-field approach, a theory which allows us to estimate the critical temperature when the anisotropic Fock potential is taken into consideration and to determine the system parameters that optimize the critical temperature at which such a superfluid emerges before the system begins to phase separate.Comment: 10 pages, 3 figure

Effects of Domain Wall on Electronic Transport Properties in Mesoscopic Wire of Metallic Ferromagnets

We study the effect of the domain wall on electronic transport properties in wire of ferromagnetic 3$d$ transition metals based on the linear response theory. We considered the exchange interaction between the conduction electron and the magnetization, taking into account the scattering by impurities as well. The effective electron-wall interaction is derived by use of a local gauge transformation in the spin space. This interaction is treated perturbatively to the second order. The conductivity contribution within the classical (Boltzmann) transport theory turns out to be negligiblly small in bulk magnets, due to a large thickness of the wall compared with the fermi wavelength. It can be, however, significant in ballistic nanocontacts, as indicated in recent experiments. We also discuss the quantum correction in disordered case where the quantum coherence among electrons becomes important. In such case of weak localization the wall can contribute to a decrease of resistivity by causing dephasing. At lower temperature this effect grows and can win over the classical contribution, in particular in wire of diameter $L_{\perp}\lesssim \ell_{\phi}$, $\ell_{\phi}$ being the inelastic diffusion length. Conductance change of the quantum origin caused by the motion of the wall is also discussed.Comment: 30 pages, 4 figures. Detailed paper of Phys. Rev. Lett. 78, 3773 (1997). Submitted to J. Phys. Soc. Jp