Thermoelectric effects in graphene with local spin-orbit interaction

We investigate the transport properties of a graphene layer in the presence of Rashba spin-orbit interaction. Quite generally, spin-orbit interactions induce spin splittings and modifications of the graphene bandstructure. We calculate within the scattering approach the linear electric and thermoelectric responses of a clean sample when the Rashba coupling is localized around a finite region. We find that the thermoelectric conductance, unlike its electric counterpart, is quite sensitive to external modulations of the Fermi energy. Therefore, our results suggest that thermocurrent measurements may serve as a useful tool to detect nonhomogeneous spin-orbit interactions present in a graphene-based device. Furthermore, we find that the junction thermopower is largely dominated by an intrinsic term independently of the spin-orbit potential scattering. We discuss the possibility of cancelling the intrinsic thermopower by resolving the Seebeck coefficient in the subband space. This causes unbalanced populations of electronic modes which can be tuned with external gate voltages or applied temperature biases.Comment: 9 pages, 8 figures. The Eq.(27) and the definition of charge thermopower have been correcte

Financial Intermediation in Muslim Community: Issues and Problems

It is widely known that Muslim society inherited an interest based financial intermediation system from others instead of developing their own banking system. However, Muslim Economists and scholars around the world made efforts to have and develop their own financial intermediation since there was no initial working model to act upon, except the belief that interest-based financial intermediation might be replaced by an Islamic one on the basis of profit-and loss sharing. During the last four decades, Islamic financial intermediation industry became a reality that the Muslim society around the world can see and practice. However, the Islamic financial intermediation in the world has been facing numerous problems of challenges. It raises a number of issues and potential problems which can be seen from the macro and micro operational point of view. Developing the Islamic financial intermediation depends on clarifying these issues and presenting them in order to focus on them studying and remedying. This paper aims to cover the ground of issues of Islamic financial intermediation that rose during its short age. Such issues prevent Islamic financial intermediation from its operating with its full efficiency level. Even no attempt to remedy these issues, presenting these issues and problems and classifying them according to their type is very valuable for sustained growth and development of the Islamic financial intermediation. Such work is a valuable contribution to build the Islamic financial intermediation industry on sound theoretical foundations.

Coulomb-blockade effect in nonlinear mesoscopic capacitors

We consider an interacting quantum dot working as a coherent source of single electrons. The dot is tunnel coupled to a reservoir and capacitively coupled to a gate terminal with an applied ac potential. At low frequencies, this is the quantum analog of the RC circuit with a purely dynamical response. We investigate the quantized dynamics as a consequence of ac pulses with large amplitude. Within a Keldysh-Green function formalism we derive the time-dependent current in the Coulomb blockade regime. Our theory thus extends previous models that considered either noninteracting electrons in nonlinear response or interacting electrons in the linear regime. We prove that the electron emission and absorption resonances undergo a splitting when the charging energy is larger than the tunnel broadening. For very large charging energies, the additional peaks collapse and the original resonances are recovered, though with a reduced amplitude. Quantization of the charge emitted by the capacitor is reduced due to Coulomb repulsion and additional plateaus arise. Additionally, we discuss the differential capacitance and resistance as a function of time. We find that to leading order in driving frequency the current can be expressed as a weighted sum of noninteracting currents shifted by the charging energy.Comment: 13 pages, 9 figures. Minor changes. Published versio

Aportació a la flora orquidiòfila de les Illes Balears

Abstract not availabl

Zoning and the Law of Nuisance

We calculate density and current spatial distributions of a 2D model junction between a normal QAH contact and a superconducting QAH region hosting propagating (chiral) Majorana modes. We use a simplified Hamiltonian describing the spatial coupling of the modes on each side of the junction, as well as the related junction conductance. We study how this coupling is affected by orbital effects caused by an external magnetic field.This work was funded by MINEICO-Spain, grant MAT2017-82639

Coastal wave storms: Observations and simulations in the NW Mediterranean

The importance of improving wind-wave predictions for the NW Mediterranean coastal region makes it necessary to perform a study in-depth of wave generation and propagation mechanisms under sharp spatial and temporal gradients. For this purpose, a heavily instrumented coastal transect was set perpendicular to Tarragona’s harbour coastline. Wave data were obtained from different buoys and meteorological stations. Wave data were analysed paying special attention to storm identification and storm evolution in terms of the integrated spectral parameters and the spectral shape. Measured data were also used to analyse the performance of the operational 18km resolution WAM wave model, and a higher resolution SWAN wave model forced with different wind fields (modelled and observed). The in-situ observations reproduced the expected features of wave generation and propagation: wave height and peak period increased with fetch during fetch-limited growth conditions and peak period was conserved in fully-developed sea conditions. Spectral shapes agreed with previous observations in both fetch-limited and fully-developed growth conditions. The differences between the time series recorded at each instrument confirm the importance of strong temporal and spatial gradients in the regional wind and wave fields. Due to the coarse temporal and spatial resolution of the operational wind and wave models, the wave model did not predict specific features of the time series such as storm peaks and calm periods, sudden changes in wave direction, and differences between instruments. Also, the operational wave model did not accurately predict the integrated spectral wave parameters: wave height was up to -50% under-predicted at the peak of the storm, low peak periods (7.5s) were under-predicted. To improve these results a high resolution wind model (4km, 3h) was used to force a high resolution wave model (1km, 1h) during one particular storm event. Increasing the resolution of the wind and wave models, the peaks of the storm were predicted and wave height estimations were significantly improved in terms of magnitude (wave height underprediction at the peak of the storm was reduced from -50% in the operational model to -17%). Some of the differences between the instruments’ time series were reproduced but not all of them. Wave height and peak period were still significantly under-predicted. Because wind speeds were over-predicted (25%), these results point to a need of improving wave predictions in terms of wave growth. For this reason, a study of the sensitivity of the wave model to different wind input fields was performed. It was concluded that modelled wind fields were better input than in-situ wind observations because of the lack of spatial variability of the observations. Also, because the observations do not represent the highest wind speeds along the fetch of the buoys. When increasing the wind (taking the highest values in the region or enhancing the predicted wind fields) better predictions of the magnitude of the wave height were obtained, although the improvements of the peak period were not conclusive. The results suggest that the reason of the under-rediction of the high-resolution models was an inaccurate transmission of energy from the winds towards the waves. The role of the drag coefficient and bimodal spectra were also considered, but its study in detail will be approached in future work. The overall results point to the need of better understanding the local wave generation and growth processes to eventually improve wave predictions in the area

Un precedente olvidado de la futura Universidad Balear: La Universidad de Montpeller : institucionalizada en 1289 bajo el reinado de Jaime II de Mallorca

Abstract not availabl