g-Factor Tuning and Manipulation of Spins by an Electric Current

We investigate the Zeeman splitting of two-dimensional electrons in an asymmetric silicon quantum well, by electron-spin-resonance (ESR) experiments. Applying a small dc current we observe a shift in the resonance field due to the additional current-induced Bychkov-Rashba (BR) type of spin-orbit (SO) field. This finding demonstrates SO coupling in the most straightforward way: in the presence of a transverse electric field the drift velocity of the carriers imposes an effective SO magnetic field. This effect allows selective tuning of the g-factor by an applied dc current. In addition, we show that an ac current may be used to induce spin resonance very efficiently.Comment: 4 pages, 4 figure

Nanoscopic Current Effects on Photovoltaics

Silicon heterojunction (SHJ) solar cells represent a promising technological approach toward higher photovoltaic efficiencies and lower fabrication cost. While the device physics of SHJ solar cells has been studied extensively in the past, the ways in which nanoscopic electronic processes such as charge-carrier generation, recombination, trapping, and percolation affect SHJ device properties macroscopically are yet to be fully understood. We report the study of atomic-scale current percolation at state-of-the-art a-Si:H/c-Si heterojunction solar cells at room temperature, revealing the profound complexity of electronic SHJ interface processes. Using conduction atomic force microscopy, it is shown that the macroscopic current–voltage characteristics of SHJ solar cells are governed by the average of local nanometer-sized percolation pathways associated with bandtail states of the doped a-Si:H selective contact leading to above bandgap local photovoltages (VOCloc) as high as 1.2 V (eVOCloc > EgapSi). This is not in violation of photovoltaic device physics but a consequence of the nature of nanometer-scale charge percolation pathways that originate from trap-assisted tunneling causing dark leakage current. We show that the broad distribution of nanoscopic local photovoltage is a direct consequence of randomly trapped charges at a-Si:H dangling bond defects, which lead to strong local potential fluctuations and induce random telegraph noise of the dark current

Perdeuteration of poly[2-methoxy-5-(2'- ethylhexyloxy)-1,4-phenylenevinylene] (d-MEH-PPV): control of microscopic charge-carrier spin–spin coupling and of magnetic-field effects in optoelectronic devices

Control of the effective local hyperfine fields in a conjugated polymer, poly[2-methoxy-5-(2 '-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), by isotopic engineering is reported. These fields, evident as a frequency-independent line broadening mechanism in electrically detected magnetic resonance (EDMR) spectroscopy, originate from the unresolved hyperfine coupling between the electronic spin of charge carrier pairs and the nuclear spins of surrounding hydrogen isotopes. The room temperature study of effects caused by complete deuteration of this polymer through magnetoresistance, magnetoelectroluminescence, coherent pulsed and multi-frequency EDMR, as well as inverse spin-Hall effect measurements, confirm the weak hyperfine broadening of charge-carrier magnetic resonance lines. As a consequence, we can resolve coherent charge-carrier spin-beating, allowing for direct measurements of the magnitude of electronic spin-spin interactions. In addition, the weak hyperfine coupling allows us to resolve substantial spin-orbit coupling effects in the EDMR spectra, even at low magnetic field strengths. These results illustrate the dramatic influence of hyperfine fields on the spin physics of organic light-emitting diode (OLED) materials at room temperature, and point to routes to reaching exotic ultra-strong resonant-drive regimes in the study of light-matter interactions

Semiconductor Spintronics

Spintronics refers commonly to phenomena in which the spin of electrons in a solid state environment plays the determining role. In a more narrow sense spintronics is an emerging research field of electronics: spintronics devices are based on a spin control of electronics, or on an electrical and optical control of spin or magnetism. This review presents selected themes of semiconductor spintronics, introducing important concepts in spin transport, spin injection, Silsbee-Johnson spin-charge coupling, and spindependent tunneling, as well as spin relaxation and spin dynamics. The most fundamental spin-dependent nteraction in nonmagnetic semiconductors is spin-orbit coupling. Depending on the crystal symmetries of the material, as well as on the structural properties of semiconductor based heterostructures, the spin-orbit coupling takes on different functional forms, giving a nice playground of effective spin-orbit Hamiltonians. The effective Hamiltonians for the most relevant classes of materials and heterostructures are derived here from realistic electronic band structure descriptions. Most semiconductor device systems are still theoretical concepts, waiting for experimental demonstrations. A review of selected proposed, and a few demonstrated devices is presented, with detailed description of two important classes: magnetic resonant tunnel structures and bipolar magnetic diodes and transistors. In most cases the presentation is of tutorial style, introducing the essential theoretical formalism at an accessible level, with case-study-like illustrations of actual experimental results, as well as with brief reviews of relevant recent achievements in the field.Comment: tutorial review; 342 pages, 132 figure

All Work and No Play? A Meta-Analytic Examination of the Correlates and Outcomes of Workaholism

Empirical research on workaholism has been hampered by a lack of consensus regarding the definition and appropriate measurement of the construct. In the present study, we first review prior conceptualizations of workaholism in an effort to identify a definition of workaholism. Then, we conduct a meta-analysis of the correlates and outcomes of workaholism to clarify its nomological network. Results indicate that workaholism is related to achievement-oriented personality traits (i.e., perfectionism, Type A personality), but is generally unrelated to many other dispositional (e.g., conscientiousness, self-esteem, positive affect) and demographic (e.g., gender, parental status, marital status) variables. Findings are mixed regarding the re