Transference of Transport Anisotropy to Composite Fermions

When interacting two-dimensional electrons are placed in a large perpendicular magnetic field, to minimize their energy, they capture an even number of flux quanta and create new particles called composite fermions (CFs). These complex electron-flux-bound states offer an elegant explanation for the fractional quantum Hall effect. Furthermore, thanks to the flux attachment, the effective field vanishes at a half-filled Landau level and CFs exhibit Fermi-liquid-like properties, similar to their zero-field electron counterparts. However, being solely influenced by interactions, CFs should possess no memory whatever of the electron parameters. Here we address a fundamental question: Does an anisotropy of the electron effective mass and Fermi surface (FS) survive composite fermionization? We measure the resistance of CFs in AlAs quantum wells where electrons occupy an elliptical FS with large eccentricity and anisotropic effective mass. Similar to their electron counterparts, CFs also exhibit anisotropic transport, suggesting an anisotropy of CF effective mass and FS.Comment: 5 pages, 5 figure

Contrast between spin and valley degrees of freedom

We measure the renormalized effective mass (m*) of interacting two-dimensional electrons confined to an AlAs quantum well while we control their distribution between two spin and two valley subbands. We observe a marked contrast between the spin and valley degrees of freedom: When electrons occupy two spin subbands, m* strongly depends on the valley occupation, but not vice versa. Combining our m* data with the measured spin and valley susceptibilities, we find that the renormalized effective Lande g-factor strongly depends on valley occupation, but the renormalized conduction-band deformation potential is nearly independent of the spin occupation.Comment: 4+ pages, 2 figure

Differential Quadrature Method For Solving Bed Load Sediment Transport

Sediment transport is crucial for designing, and operating hydraulic structures. Hence, itsprediction has forced researches to study it through experimental and mathematical modeling works. Mathematical modeling has gained importance especially with the advent of powerfulcomputers. These modeling studies are mostly based on the numerical solutions of transport equations of the partial differential equations with finite difference, finite element or finite volume methods. This study, as an alternative to existing methods, has developed a numerical technique, called differential quadrature method (DQM). The DQM expresses a differential at apoint as a function of products of weight coefficients and the functional values at each point ofthe domain. The weight coefficients are determined using one of the several algorithms such asthe Langrangian, depending upon the spacing intervals. In this study, bed load sediment transport equation, coupled with flow equations of the continuity and momentum, is solved using the DQM. The performance of the model is tested against that of the finite difference method and aswell as the experimental data. The results revealed that DQM can also be employed in modeling bed load sediment transport

Suns-VOC_\textrm{OC} characteristics of high performance kesterite solar cells

Low open circuit voltage ($V_{OC}$) has been recognized as the number one problem in the current generation of Cu$_{2}$ZnSn(Se,S)$_{4}$ (CZTSSe) solar cells. We report high light intensity and low temperature Suns-$V_{OC}$ measurement in high performance CZTSSe devices. The Suns-$V_{OC}$ curves exhibit bending at high light intensity, which points to several prospective $V_{OC}$ limiting mechanisms that could impact the $V_{OC}$, even at 1 sun for lower performing samples. These V$_{OC}$ limiting mechanisms include low bulk conductivity (because of low hole density or low mobility), bulk or interface defects including tail states, and a non-ohmic back contact for low carrier density CZTSSe. The non-ohmic back contact problem can be detected by Suns-$V_{OC}$ measurements with different monochromatic illumination. These limiting factors may also contribute to an artificially lower $J_{SC}$-$V_{OC}$ diode ideality factor.Comment: 9 pages, 9 figures, 1 supplementary materia

Double Decomposition Method for the Solution of Sediment Wave Equation

Transient sediment waves are solved by the double decomposition (DD) method. The method solves the parabolic partial differential equation by decomposing the solution function into summation of M number of components. The solution is approximated by considering the first three terms. The performance of the model in simulating experimental data is satisfactory.The hypothetical case study reveals that the model can mimic the sediment transport in nature

The Relationship between Foreign Direct Investment and Economic Growth: A Case of Turkey

This paper examines the relationship between net FDI inflows and real GDP for Turkey from 1970 to 2019. Although conventional economic growth theories and most empirical research suggest that there is a bi-directional positive effect between these macro variables, the results indicate that there is a uni-directional significant short-run positive effect of real GDP on net FDI inflows to Turkey by employing the Vector Error Correction Model, Granger Causality, Impulse Response Functions and Variance Decomposition. Also, there is no long-run effect has been found. The findings recommend Turkish authorities optimally benefit from the potential positive effect of net incoming FDI on the real GDP by allocating it for the productive sectoral establishments while effectively maintaining the country's real economic growth to attract further FDI inflows

Density dependence of valley polarization energy for composite fermions

In two-dimensional electron systems confined to wide AlAs quantum wells, composite fermions around the filling factor $\nu$ = 3/2 are fully spin polarized but possess a valley degree of freedom. Here we measure the energy needed to completely valley polarize these composite fermions as a function of electron density. Comparing our results to the existing theory, we find overall good quantitative agreement, but there is an unexpected trend: The measured composite fermion valley polarization energy, normalized to the Coulomb energy, decreases with decreasing density