1,955 research outputs found
Quasiparticle Band Structure and Density Functional Theory: Single-Particle Excitations and Band Gaps in Lattice Models
We compare the quasiparticle band structure for a model insulator obtained
from the fluctuation exchange approximation (FEA) with the eigenvalues of the
corresponding density functional theory (DFT) and local density approximation
(LDA). The discontinuity in the exchange-correlation potential for this model
is small and the FEA and DFT band structures are in good agreement. In contrast
to conventional wisdom, the LDA for this model overestimates the size of the
band gap. We argue that this is a consequence of an FEA self-energy that is
strongly frequency dependent, but essentially local.Comment: 8 pages, and 5 figure
Ferromagnetic imprinting of spin polarization in a semiconductor
We present a theory of the imprinting of the electron spin coherence and
population in an n-doped semiconductor which forms a junction with a
ferromagnet. The reflection of non-equilibrium semiconductor electrons at the
interface provides a mechanism to manipulate the spin polarization vector. In
the case of unpolarized excitation, this ballistic effect produces spontaneous
electron spin coherence and nuclear polarization in the semiconductor, as
recently observed by time-resolved Faraday rotation experiments. We investigate
the dependence of the spin reflection on the Schottky barrier height and the
doping concentration in the semiconductor and suggest control mechanisms for
possible device applications.Comment: 4 pages with 2 figure
Maximum Entropy Correlated Equilibria
We study maximum entropy correlated equilibria in (multi-player)games and provide two gradient-based algorithms that are guaranteedto converge to such equilibria. Although we do not provideconvergence rates for these algorithms, they do have strong connectionsto other algorithms (such as iterative scaling) which are effectiveheuristics for tasks such as statistical estimation
Optical RKKY Interaction between Charged Semiconductor Quantum Dots
We show how a spin interaction between electrons localized in neighboring
quantum dots can be induced and controlled optically. The coupling is generated
via virtual excitation of delocalized excitons and provides an efficient
coherent control of the spins. This quantum manipulation can be realized in the
adiabatic limit and is robust against decoherence by spontaneous emission.
Applications to the realization of quantum gates, scalable quantum computers,
and to the control of magnetization in an array of charged dots are proposed.Comment: 4 pages, 2 figure
Coherently photo-induced ferromagnetism in diluted magnetic semiconductors
Ferromagnetism is predicted in undoped diluted magnetic semiconductors
illuminated by intense sub-bandgap laser radiation . The mechanism for
photo-induced ferromagnetism is coherence between conduction and valence bands
induced by the light which leads to an optical exchange interaction. The
ferromagnetic critical temperature T_C depends both on the properties of the
material and on the frequency and intensity of the laser and could be above 1
K.Comment: 11 pages, 2 figures, preprint styl
Many-body diagrammatic expansion in a Kohn-Sham basis: implications for Time-Dependent Density Functional Theory of excited states
We formulate diagrammatic rules for many-body perturbation theory which uses
Kohn-Sham (KS) Green's functions as basic propagators. The diagram technique
allows to study the properties of the dynamic nonlocal exchange-correlation
(xc) kernel . We show that the spatial non-locality of is
strongly frequency-dependent. In particular, in extended systems the
non-locality range diverges at the excitation energies. This divergency is
related to the discontinuity of the xc potential.Comment: 4 RevTeX pages including 3 eps figures, submitted to Phys. Rev. Lett;
revised version with new reference
Emerging role of microRNAs in diagnosis and treatment of various diseases including ovarian cancer
MicroRNAs (miRNAs) represent a class of small non-coding RNAs that control gene expression by targeting messenger RNA (mRNA). Recently, it has been demonstrated that miRNA expression is altered in many human diseases including cancers, suggesting that miRNA may play a potential role in the pathogenesis of different diseases. It has also been reported that there is a unique expression pattern of miRNAs in the disease state differing from the normal state. In this review, we focus on the miRNA signatures in different human diseases including cancers. Such signatures may be used as diagnostic and prognostic markers
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