30 research outputs found
Measurement of Rashba and Dresselhaus spin-orbit magnetic fields
Spin-orbit coupling is a manifestation of special relativity. In the
reference frame of a moving electron, electric fields transform into magnetic
fields, which interact with the electron spin and lift the degeneracy of
spin-up and spin-down states. In solid-state systems, the resulting spin-orbit
fields are referred to as Dresselhaus or Rashba fields, depending on whether
the electric fields originate from bulk or structure inversion asymmetry,
respectively. Yet, it remains a challenge to determine the absolute value of
both contributions in a single sample. Here we show that both fields can be
measured by optically monitoring the angular dependence of the electrons' spin
precession on their direction of movement with respect to the crystal lattice.
Furthermore, we demonstrate spin resonance induced by the spin-orbit fields. We
apply our method to GaAs/InGaAs quantum-well electrons, but it can be used
universally to characterise spin-orbit interactions in semiconductors,
facilitating the design of spintronic devices
Dynamical spin-electric coupling in a quantum dot
Due to the spin-orbital coupling in a semiconductor quantum dot, a freely
precessing electron spin produces a time-dependent charge density. This creates
a sizeable electric field outside the dot, leading to promising applications in
spintronics. The spin-electric coupling can be employed for non-invasive single
spin detection by electrical methods. We also consider a spin relaxation
mechanism due to long-range coupling to electrons in gates and elsewhere in the
system, and find a contribution comparable to, and in some cases dominant over
previously discussed mechanisms.Comment: 4 pages, 2 figure
Theory of electrical spin injection: Tunnel contacts as a solution of the conductivity mismatch problem
Theory of electrical spin injection from a ferromagnetic (FM) metal into a
normal (N) conductor is presented. We show that tunnel contacts (T) can
dramatically increase spin injection and solve the problem of the mismatch in
the conductivities of a FM metal and a semiconductor microstructure. We also
present explicit expressions for the spin-valve resistance of FM-T-N- and
FM-T-N-T-FM-junctions with tunnel contacts at the interfaces and show that the
resistance includes both positive and negative contributions (Kapitza
resistance and injection conductivity, respectively).Comment: 4 pages, to appear in Phys. Rev. B (rapid communications
Spintronics: Fundamentals and applications
Spintronics, or spin electronics, involves the study of active control and
manipulation of spin degrees of freedom in solid-state systems. This article
reviews the current status of this subject, including both recent advances and
well-established results. The primary focus is on the basic physical principles
underlying the generation of carrier spin polarization, spin dynamics, and
spin-polarized transport in semiconductors and metals. Spin transport differs
from charge transport in that spin is a nonconserved quantity in solids due to
spin-orbit and hyperfine coupling. The authors discuss in detail spin
decoherence mechanisms in metals and semiconductors. Various theories of spin
injection and spin-polarized transport are applied to hybrid structures
relevant to spin-based devices and fundamental studies of materials properties.
Experimental work is reviewed with the emphasis on projected applications, in
which external electric and magnetic fields and illumination by light will be
used to control spin and charge dynamics to create new functionalities not
feasible or ineffective with conventional electronics.Comment: invited review, 36 figures, 900+ references; minor stylistic changes
from the published versio
Powers of Romance: The Liminal Challenges of Managing Organizational Intimacy
© The Author(s) 2014 Problematic organizational relationships have recently been at the core of highly visible media coverage. Most analyses of sexual relations in organizations have been, however, simplistic and unidimensional, and have placed insufficient systematic emphasis on the role of governmentality in the social construction of organizational romance. In this article, we proceed in two theoretical steps. First, we elaborate a typology of organizational romance that covers different manifestations of this nuanced process. We think of these as organizational strategies of governmentality. Second, we elaborate and identify liminal cases that fall into the interstices of the four predominant ways of managing sexual relationships in organizations. We think of these as vases of liquid love and life that evade the border controls of regulation by governmentality. Finally, we relate these issues to debates about the nature of the civilizational process and suggest hypotheses for future research
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
Characterization of microRNAs encoded by the bovine herpesvirus 1 genome
Bovine herpesvirus 1 (BoHV-1) is a ubiquitous and important pathogen of cattle worldwide. This study reports the identification of 10 microRNA (miRNA) genes, Bhv1-mir-B1–Bhv1-mir-B10, encoded by the BoHV-1 genome that were processed into 12 detectable mature miRNAs as determined by ultra-high throughput sequencing bioinformatics analyses of small RNA libraries and expression studies. We found that four of the miRNA genes were present as two copies in the BoHV-1 genome, resulting in a total of 14 miRNA encoding loci. Unique features of the BoHV-1 miRNAs include evidence of bidirectional transcription and a close association of two miRNA genes with the origin of replication, including one miRNA that is encoded within the origin of replication. The miRNA gene Bhv1-mir-B5 was encoded on the opposite DNA strand to the latency associated transcript, potentially giving rise to antisense transcripts originating from this locus. The association of herpesvirus miRNAs with latency appears to be a common feature in the alphaherpesviruses. Analyses of the BoHV-5 genome for putative miRNA gene orthologues identified a high degree of evolutionary conservation for nine of the BoHV-1 miRNA genes. The possible roles for BoHV-1 miRNAs in the regulation of known BoHV-1 transcription units and the genetics of the BoHV-1 genotypes are also discussed
Foreign competition, domestic competition and innovation in Chinese private high-tech new ventures
Competition plays an important role in creating conditions favourable to innovation. However, is this the case for all types of competition? While recognizing the importance of competition in innovation, we address this question by examining the impact of foreign and domestic competition on the innovation performance of private high-tech new ventures. We argue that the impact of foreign and domestic competition on the innovation performance of local private firms may vary, due to the different types of resource interdependence with their competitors and learning gained by private firms. To test these arguments, we conducted a multilevel analysis of 805 Chinese private high-tech firms over the period 2001-2007. Our findings suggest that foreign competition has a U-shaped relationship with the innovation performance of private firms, whereas competition from state-owned enterprises positively affects private firms' innovation performance. Our study moves beyond the debate on whether competition increases or decreases innovation by unpacking the differential effects exerted by different types of competitors on the innovation performance of local private firms in the context of a transition economy