Orbitronics: the Intrinsic Orbital Hall Effect in p-Doped Silicon

The spin Hall effect depends crucially on the intrinsic spin-orbit coupling of the energy band. Because of the smaller spin-orbit coupling in silicon, the spin Hall effect is expected to be much reduced. We show that the electric field in p-doped silicon can induce a dissipationless orbital current in a fashion reminiscent of the spin Hall effect. The vertex correction due to impurity scattering vanishes and the effect is therefore robust against disorder. The orbital Hall effect can lead to the accumulation of local orbital momentum at the edge of the sample, and can be detected by the Kerr effect.Comment: 4 page

Generic Phase Diagram of Fermion Superfluids with Population Imbalance

It is shown by microscopic calculations for trapped imbalanced Fermi superfluids that the gap function has always sign changes, i.e., the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state like, up to a critical imbalance $P_c$, beyond which normal state becomes stable, at temperature T=0. A phase diagram is constructed in $T$ vs $P$, where the BCS state without sign change is stable only at $T\neq 0$. We reproduce the observed bimodality in the density profile to identify its origin and evaluate $P_c$ as functions of $T$ and the coupling strength. These dependencies match with the recent experiments.Comment: 5 pages, 5 figures, replaced by the version to appear in PR

The phase diagram of the massive Gross-Neveu model, revisited

The massive Gross-Neveu model is solved in the large N limit at finite temperature and chemical potential. The phase diagram features a kink-antikink crystal phase which was missed in previous works. Translated into the framework of condensed matter physics our results generalize the bipolaron lattice in non-degenerate conducting polymers to finite temperature.Comment: revtex, 4 pages, 3 figures; v2: minor typos corrected; v3: minor corrections concerning figures 2 and

Acoustic Cyclotron Resonance and Giant High Frequency Magnetoacoustic Oscillations in Metals with Locally Flattened Fermi Surface

We consider the effect of local flattening on the Fermi surface (FS) of a metal upon geometric oscillations of the velocity and attenuation of ultrasonic waves in the neighborhood of the acoustic cyclotron resonance. It is shown that such peculiarities of the local geometry of the FS can lead to a significant enhancement of both cyclotron resonance and geometric oscillations. Characteristic features of the coupling of ultrasound to shortwave cyclotron waves arising due to the local flattening of the FS are analyzed. PACS numbers 71.18.+y; 72.15.Gd; 72.15.-vComment: 8 pages, 3 figures, text revise

One Dimensional Chain with Long Range Hopping

The one-dimensional (1D) tight binding model with random nearest neighbor hopping is known to have a singularity of the density of states and of the localization length at the band center. We study numerically the effects of random long range (power-law) hopping with an ensemble averaged magnitude \expectation{|t_{ij}|} \propto |i-j|^{-\sigma} in the 1D chain, while maintaining the particle-hole symmetry present in the nearest neighbor model. We find, in agreement with results of position space renormalization group techniques applied to the random XY spin chain with power-law interactions, that there is a change of behavior when the power-law exponent $\sigma$ becomes smaller than 2

On the Incommensurate Phase of Pure and Doped Spin-Peierls System CuGeO_3

Phases and phase transitions in pure and doped spin-Peierls system CuGeO_3 are considered on the basis of a Landau-theory. In particular we discuss the critical behaviour, the soliton width and the low temperature specific heat of the incommensurate phase. We show, that dilution leads always to the destruction of long range order in this phase, which is replaced by an algebraic decay of correlations if the disorder is weak.Comment: 4 pages revtex, no figure

Study-related Use of Instructional Videos by Undergraduate Engineering Students

[EN] In this paper, a questionnaire-based survey on the use of online videos by undergraduate engineering students for study-related purposes is presented. Over the last few years, a large number of instructional videos has been uploaded to websites such as YouTube. Due to the widespread distribution of high-speed internet connections and (mobile) devices, such as smartphones or laptops, which are nowadays routinely used by students, online videos are also frequently used in higher education. While much research on this subject focuses on Massive Open Online Courses (MOOCs) or flipped classroom approaches, this survey examines use of videos for self-study, complementary to traditional face-to-face courses. Furthermore, we analyze the acceptance of a characteristic video production style, which uses specific 3D animations to clarify complex connections between technical and mathematical aspects. The results indicate extensive use of short videos which address subjects that are particularly difficult for the students. This survey can help educators to develop an impression of current video use by undergraduate engineering students. In this paper, a questionnaire-based survey on the use of online videos by undergraduate engineering students for study-related purposes is presented. Especially over the last few years, a large number of instructional videos has been uploaded to websites such as YouTube. Due to the widespread distribution of high-speed internet connections and (mobile) devices, such as smartphones or laptops, which are nowadays routinely used by students, online videos are also frequently used in higher education. While much research on this subject focuses on Massive Open Online Courses (MOOCs) or flipped classroom approaches, this survey examines usage behavior concerning the apparently much more common use of videos for self-study, complementary to traditional face-to-face courses. Furthermore, we analyze the acceptance of a characteristic video production style using specific 3D animations to clarify complex connections between technical and mathematical aspects. The results indicate that short videos addressing subjects that are particularly difficult for the students are extensively used. Additionally, this survey can help educators to develop a realistic understanding of current video use by undergraduate engineering students.http://ocs.editorial.upv.es/index.php/HEAD/HEAD18Hennig, M.; Mertsching, B. (2018). Study-related Use of Instructional Videos by Undergraduate Engineering Students. Editorial Universitat Politècnica de València. 1377-1385. https://doi.org/10.4995/HEAD18.2018.8207OCS1377138

The Bogoliubov/de Gennes system, the AKNS hierarchy, and nonlinear quantum mechanical supersymmetry

We show that the Ginzburg-Landau expansion of the grand potential for the Bogoliubov-de Gennes Hamiltonian is determined by the integrable nonlinear equations of the AKNS hierarchy, and that this provides the natural mathematical framework for a hidden nonlinear quantum mechanical supersymmetry underlying the dynamics.Comment: 25 pages, 4 figures; published versio