Localization-delocalization transitions in a two-dimensional quantum percolation model: von Neumann entropy studies
Longyan Gong and Peiqing Tong
In two-dimensional quantum site-percolation square lattice models, the von Neumann entropy is extensively studied numerically. At a certain eigenenergy, the localization-delocalization transition is reflected by the derivative of von Neumann entropy which is maximal at the quantum percolation thresh ... [Phys. Rev. B 80, 174205 (2009)] published Fri Nov 20, 2009.
Field-Induced Kosterlitz-Thouless Transition in the N=0 Landau Level of Graphene
Kentaro Nomura, Shinsei Ryu, and Dung-Hai Lee
At the charge neutral point, graphene exhibits a very unusual high-resistance metallic state and a transition to a complete insulating phase in a strong magnetic field. We propose that the current carriers in this state are the charged vortices of the XY valley-pseudospin order parameter, a situatio ... [Phys. Rev. Lett. 103, 216801 (2009)] published Fri Nov 20, 2009.
Thermodynamics of the thermoelectric potential
Christophe Goupil
We derive the principal contributions to energy flux and entropy flux in a thermoelectric material using a force-flux description. Using the reduced current u=J/kappa[del]T of the coupled thermal and electrical flows, we introduce the so-called thermoelectric potential Talpha+1/u. We show that this ... [J. Appl. Phys. 106, 104907 (2009)] published Fri Nov 20, 2009.
First-principles simulations on bulk TaO and Cu/TaO/Pt heterojunction: Electronic structures and transport properties
Tingkun Gu, Zhongchang Wang, Tomofumi Tada, and Satoshi Watanabe
Electronic structures and transport properties of bulk TaO and Cu/TaO/Pt heterojunction have been studied from first principles. Of the two room-temperature phases of bulk TaO, beta-, and delta-TaO, our calculated results showed that the beta phase has much narrower band gap than the delta-TaO. For ... [J. Appl. Phys. 106, 103713 (2009)] published Fri Nov 20, 2009.
Photoinduced spin-polarized current in InSb-based structures
M. Frazier, J. G. Cates, J. A. Waugh, J. J. Heremans, M. B. Santos et al.
We demonstrate the observation of spin-polarized photocurrent in InSb films grown on GaAs and InP substrates and InSb quantum wells where a nonequilibrium spin population has been achieved by using circularly polarized radiation. The characteristics of our observations indicated that the circular ph ... [J. Appl. Phys. 106, 103513 (2009)] published Fri Nov 20, 2009.
A method for evaluating the ground state excitonic band gaps of strained InGaN/GaN quantum wells
T. K. Sharma and E. Towe
A simple method for calculating the ground state excitonic band gaps of strained wurtzite InGaN/GaN quantum wells (QWs) for the entire composition range is proposed. The modification of the electronic band structure due to strain becomes significant for high values of indium concentration. It is obs ... [J. Appl. Phys. 106, 104509 (2009)] published Fri Nov 20, 2009.
Modeling charge-imbalanced NaNbO/SrTiO superlattices: Lattice relaxation and metallicity
Riku Oja and Risto M. Nieminen
The electronic and structural properties of different charge-imbalanced perovskite oxide NaNbO/SrTiO superlattices are investigated with density-functional theory (local density approximation and local spin density approximation+U) methods. Metallic or insulating behavior of such a superlattice depe ... [Phys. Rev. B 80, 205420 (2009)] published Thu Nov 19, 2009.
Terahertz photoresponse of a quantum Hall edge-channel diode
Christian Notthoff, Kevin Rachor, Detlef Heitmann, and Axel Lorke
The terahertz (THz) photoresponse of a two-dimensional electron gas in the quantum Hall regime is investigated. We use a sample structure which is topologically equivalent to a Corbino geometry combined with a cross-gate technique. This quasi-Corbino geometry allows us to directly investigate the TH ... [Phys. Rev. B 80, 205320 (2009)] published Thu Nov 19, 2009.
Influence of the substrate bands on the sp-levels topology of Ag films on Ge(111)
P. Moras, D. Topwal, P. M. Sheverdyaeva, L. Ferrari, J. Fujii et al.
Angle-resolved photoemission spectroscopy and first-principles calculations were employed to analyze unusual features in the electronic structure of ultrathin Ag films grown on Ge(111). The Ag sp-derived quantum well states exhibit hexagonal-like constant energy contours with different in-plane orie ... [Phys. Rev. B 80, 205418 (2009)] published Thu Nov 19, 2009.
GW investigation of interface-induced correlation effects on transport properties in realistic nanoscale structures
Changsheng Li, M. Bescond, and M. Lannoo
We report a theoretical investigation of long-range correlation effects induced by the presence of interfaces in realistic semiconductor based nanoscale structures. This is performed within the so-called GW approximation of Hedin and Lundqvist in which we isolate the contribution of the interfaces w ... [Phys. Rev. B 80, 195318 (2009)] published Thu Nov 19, 2009.
Spin-charge decoupling and the photoemission line-shape in one-dimensional insulators
Valeria Lante and Alberto Parola
The recent advances in angle-resolved photoemission techniques allowed the unambiguous experimental confirmation of spin-charge decoupling in quasi-one-dimensional (1D) Mott insulators. This opportunity stimulates a quantitative analysis of the spectral function A(k,omega) of prototypical one-dimens ... [Phys. Rev. B 80, 195113 (2009)] published Thu Nov 19, 2009.
Statistics of quantum transfer of noninteracting fermions in multiterminal junctions
Dania Kambly and D. A. Ivanov
Similarly to the recently obtained result for two-terminal systems, we show that there are constraints on the full counting statistics for noninteracting fermions in multiterminal contacts. In contrast to the two-terminal result, however, there is no factorization property in the multiterminal case. ... [Phys. Rev. B 80, 193306 (2009)] published Thu Nov 19, 2009.
Exciton diffusion in energetically disordered organic materials
Stavros Athanasopoulos, Evguenia V. Emelianova, Alison B. Walker, and David Beljonne
We implement a simple, continuous, analytical model for exciton hopping in an energetically disordered molecular landscape. The model is parameterized against atomistic and lattice Monte Carlo simulations based on quantum-chemical calculations. It captures the essential physics of exciton diffusion ... [Phys. Rev. B 80, 195209 (2009)] published Thu Nov 19, 2009.
Electronic structure of substitutional Mn in epitaxial InMnSb film
N. D. Parashar, D. J. Keavney, and B. W. Wessels
The magnetic and electronic structure of Mn in InMnSb ferromagnetic semiconductor thin film was studied by x-ray absorption spectroscopy and x-ray magnetic circular dichroism. Comparison with atomic multiplet calculations suggests that manganese substitutes on sites with tetrahedral symmetry. Strong ... [Appl. Phys. Lett. 95, 201905 (2009)] published Thu Nov 19, 2009.
Four discrete Hall resistance states in single-layer Fe film for quaternary memory devices
Taehee Yoo, S. Khym, Sun-young Yea, Sunjae Chung, Sanghoon Lee et al.
We report the realization of four distinct magnetic states using single layers of Fe at room temperature. When the Fe film was grown on the vicinal surface of GaAs, the fourfold-symmetric magnetization along crystallographic direction give rise to four distinct Hall resistance values due to the diff ... [Appl. Phys. Lett. 95, 202505 (2009)] published Thu Nov 19, 2009.
Diffusion and Ballistic Transport in One-Dimensional Quantum Systems
J. Sirker, R. G. Pereira, and I. Affleck
It has been conjectured that transport in integrable one-dimensional systems is necessarily ballistic. The large diffusive response seen experimentally in nearly ideal realizations of the S=1/2 1D Heisenberg model is therefore puzzling and has not been explained so far. Here, we show that, contrary ... [Phys. Rev. Lett. 103, 216602 (2009)] published Thu Nov 19, 2009.
Field-Induced Orbital Antiferromagnetism in Mott Insulators
K. A. Al-Hassanieh, C. D. Batista, G. Ortiz, and L. N. Bulaevskii
We report on a new electromagnetic phenomenon that emerges in Mott insulators. The phenomenon manifests as antiferromagnetic ordering due to orbital electric currents which are spontaneously generated from the coupling between spin currents and an external homogenous magnetic field. This novel spin- ... [Phys. Rev. Lett. 103, 216402 (2009)] published Thu Nov 19, 2009.
Dirac electrons in a Kronig-Penney potential: Dispersion relation and transmission periodic in the strength of the barriers
M. Barbier, P. Vasilopoulos, and F. M. Peeters
The transmission T and conductance G through one or multiple one-dimensional, delta-function barriers of two-dimensional fermions with a linear energy spectrum are studied. T and G are periodic functions of the strength P of the delta-function barrier V(x,y)/[h-bar]v=Pdelta(x). The dispersion relati ... [Phys. Rev. B 80, 205415 (2009)] published Wed Nov 18, 2009.
Gamma valence band symmetry related hole fine splitting of bound excitons in ZnO observed in magneto-optical studies
Markus R. Wagner, Jan-Hindrik Schulze, Ronny Kirste, Munise Cobet, Axel Hoffmann et al.
The symmetry ordering of the valence bands in ZnO is derived from high-resolution magneto-optical measurements of bound excitons. We report on the experimental observation of a hole state related fine splitting for bound excitons in the Voigt configuration. This splitting is related to a nonzero Lan ... [Phys. Rev. B 80, 205203 (2009)] published Wed Nov 18, 2009.
Controlling and enhancing terahertz collective electron dynamics in superlattices by chaos-assisted miniband transport
M. T. Greenaway, A. G. Balanov, E. Scholl, and T. M. Fromhold
We show that a tilted magnetic field transforms the structure and THz dynamics of charge domains in a biased semiconductor superlattice. At critical field values, strong coupling between the Bloch and cyclotron motion of a miniband electron triggers chaotic delocalization of the electron orbits, cau ... [Phys. Rev. B 80, 205318 (2009)] published Wed Nov 18, 2009.
Masses in graphenelike two-dimensional electronic systems: Topological defects in order parameters and their fractional exchange statistics
Shinsei Ryu, Christopher Mudry, Chang-Yu Hou, and Claudio Chamon
We classify all possible 36 gap-opening instabilities in graphenelike structures in two dimensions, i.e., masses of Dirac Hamiltonian when the spin, valley, and superconducting channels are included. These 36 order parameters break up into 56 possible quintuplets of masses that add in quadrature and ... [Phys. Rev. B 80, 205319 (2009)] published Wed Nov 18, 2009.
Phonon-assisted transitions from quantum dot excitons to cavity photons
Ulrich Hohenester, Arne Laucht, Michael Kaniber, Norman Hauke, Andre Neumann et al.
For a single semiconductor quantum dot embedded in a microcavity, we theoretically and experimentally investigate phonon-assisted transitions between excitons and the cavity mode. Within the framework of the independent boson model we find that such transitions can be very efficient, even for relati ... [Phys. Rev. B 80, 201311 (2009)] published Wed Nov 18, 2009.
Coherent transport in semiconductor heterostructures: A phenomenological approach
Ariel Gordon and Daniel Majer
We propose a theoretical method for describing coherent quantum transport in semiconductor heterostructures and particularly in quantum cascade lasers (QCLs). The method is an extension of standard rate-equation models to include coherence. Instead of building the model from microscopic consideratio ... [Phys. Rev. B 80, 195317 (2009)] published Wed Nov 18, 2009.
Hard energy gap and current-path switching in ordered two-dimensional nanodot arrays prepared by focused electron-beam-induced deposition
Roland Sachser, Fabrizio Porrati, and Michael Huth
We present electronic transport measurements on ordered two-dimensional nanodot arrays with dot diameters of about 20 nm prepared by focused electron-beam-induced deposition (FEBID). Low-temperature conductance measurements and I/V characteristics strongly indicate that single electron transport thr ... [Phys. Rev. B 80, 195416 (2009)] published Wed Nov 18, 2009.
Effects of repulsive and attractive ionized impurities on the resistivity of semiconductor heterostructures in the quantum Hall regime
A. Raymond, I. Bisotto, Y. M. Meziani, S. Bonifacie, C. Chaubet et al.
We have investigated experimentally and theoretically the effect of repulsive and attractive ionized impurities on the resistivity components (rho and rho) in the quantum Hall effect regime. GaAs/GaAlAs asymmetric modulation-doped quantum wells with additional delta doping (by Si donor atoms or Be a ... [Phys. Rev. B 80, 195316 (2009)] published Wed Nov 18, 2009.
Localized atomic basis set in the projector augmented wave method
A. H. Larsen, M. Vanin, J. J. Mortensen, K. S. Thygesen, and K. W. Jacobsen
We present an implementation of localized atomic-orbital basis sets in the projector augmented wave (PAW) formalism within the density-functional theory. The implementation in the real-space GPAW code provides a complementary basis set to the accurate but computationally more demanding grid represen ... [Phys. Rev. B 80, 195112 (2009)] published Wed Nov 18, 2009.
Charge transport in polypyrrole:ZnO-nanowires composite films
A. Singh, Aditee Joshi, S. Samanta, A. K. Debnath, D. K. Aswal et al.
Low temperature electrical transport properties of composite polypyrrole (PPy) films having ZnO-nanowires (ZnONWs) in the range of 050 wt. % have been investigated. It has been found that pure PPy film is in the critical regime of the metal-to-insulator transition, and adding ZnONWs drive composite ... [Appl. Phys. Lett. 95, 202106 (2009)] published Wed Nov 18, 2009.
Electronic properties and open-circuit voltage enhancement in mixed copper phthalocyanine:fullerene bulk heterojunction photovoltaic devices
T. W. Ng, M. F. Lo, M. K. Fung, S. L. Lai, Z. T. Liu et al.
While bulk heterojunctions (HJ) have been used in organic photovoltaic (OPV) devices, there are few studies on their interface electronics and mechanisms on device performance. Here, we studied the electronic structure of a mixed CuPc:C and a discrete CuPc/C junctions using photoemission spectroscop ... [Appl. Phys. Lett. 95, 203303 (2009)] published Wed Nov 18, 2009.
Aggregates-induced dynamic negative differential resistance in conducting organic films
Xian Ning Xie, Junzhong Wang, Kian Ping Loh, and Andrew Thye Shen Wee
This letter reports the negative differential resistance (NDR) behavior of perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride films induced by aggregate formation in the film. It is observed that aggregate-states in the energy gap can by-pass the common charge conduction mode, and electron injec ... [Appl. Phys. Lett. 95, 203302 (2009)] published Wed Nov 18, 2009.
Microwave conductance spectra of single-walled carbon nanotube arrays
Clark Highstrete, Mark Lee, A. Alec Talin, and Andrew L. Vance
Complex conductance spectra of single-walled carbon nanotube (SWCNT) arrays have been measured from 0.1 to 50 GHz at temperatures between 4 and 293 K. Using purely capacitive contacts to separate contact effects from the NTs' response, the intrinsic SWCNT array conductance increased with frequency a ... [Appl. Phys. Lett. 95, 203111 (2009)] published Wed Nov 18, 2009.
Direct measurement of auger recombination in InGaN/GaN quantum wells and its impact on the efficiency of InGaN/GaN multiple quantum well light emitting diodes
M. Zhang, P. Bhattacharya, J. Singh, and J. Hinckley
The Auger recombination coefficient in InGaN/GaN quantum wells, emitting at 407 nm has been determined from large signal modulation measurements on lasers in which these quantum wells form the gain region. A value of 1.5 x 10 cm s is determined for the Auger coefficient at room temperature, which i ... [Appl. Phys. Lett. 95, 201108 (2009)] published Wed Nov 18, 2009.
Schottky's conjecture on multiplication of field enhancement factors
Ryan Miller, Y. Y. Lau, and John H. Booske
Of great interest to high power microwave, millimeter wave to terahertz sources, x-ray tubes, electrons guns, etc., is the electric field enhancement obtained from sharp emitting structures fabricated by various microfabrication methods. In this paper, we use conformal mapping to investigate the fie ... [J. Appl. Phys. 106, 104903 (2009)] published Wed Nov 18, 2009.
Concept and operation of Schottky emitter without suppressor electrode
A. K. Dokania and P. Kruit
The Schottky electron emitter is the most frequently used electron source in electron microscopes. A suppressor electrode around the emitter is usually employed to prevent emission from the shank of the cathode. A concept of operating the Schottky emitter without the suppressor electrode is proposed ... [J. Vac. Sci. Technol. B 27, 2426 (2009)] published Wed Nov 18, 2009.
Bipolar resistive switching in individual AuNiOAu segmented nanowires
Edward D. Herderick, Kongara M. Reddy, Rachel N. Sample, Thomas I. Draskovic, and Nitin P. Padture
Evidence for bipolar resistive switching is reported in individual metal-oxide-metal (MOM) nanowires in the system AuNiOAu, and a plausible mechanism for the same is presented. The MOM nanowire architecture may be well suited for much needed fundamental studies of resistive switching because it prov ... [Appl. Phys. Lett. 95, 203505 (2009)] published Tue Nov 17, 2009.
Hyperfine-induced valley mixing and the spin-valley blockade in carbon-based quantum dots
Andras Palyi and Guido Burkard
Hyperfine interaction (HFI) in carbon nanotube and graphene quantum dots is due to the presence of C atoms. We theoretically show that in these structures the short-range nature of the HFI gives rise to a coupling between the valley degree of freedom of the electron and the nuclear spin, in addition ... [Phys. Rev. B 80, 201404 (2009)] published Tue Nov 17, 2009.
Bilayer quantum Hall system at nu=1: Pseudospin models and in-plane magnetic field
O. Tieleman, A. Lazarides, D. Makogon, and C. Morais Smith
We investigate two theoretical pseudomagnon-based models for a bilayer quantum Hall system (BQHS) at total filling factor nu=1. We find a unifying framework which elucidates the different approximations that are made. We also consider the effect of an in-plane magnetic field in BQHSs at nu=1, by der ... [Phys. Rev. B 80, 205315 (2009)] published Tue Nov 17, 2009.
Defect-induced optical absorption in the visible range in ZnO nanowires
R. Michael Sheetz, Inna Ponomareva, Ernst Richter, Antonis N. Andriotis, and Madhu Menon
The optical properties of ZnO nanowires containing defects are investigated using first-principles density-functional theory incorporating the LDA+U formalism. Calculations include defects in the form of substitutional N, Zn, and O vacancies as well as +1 charged O vacancy. Our calculations reveal t ... [Phys. Rev. B 80, 195314 (2009)] published Tue Nov 17, 2009.
Nonadiabatic spin-transfer torque in (Ga,Mn)As with perpendicular anisotropy
J.-P. Adam, N. Vernier, J. Ferre, A. Thiaville, V. Jeudy et al.
Current-induced magnetic domain wall motion has been investigated in microtracks made from a ferromagnetic semiconductor (Ga,Mn)As thin film with perpendicular anisotropy. In order to reveal the nature of this motion, small fields were additionally applied. The results demonstrate that, when driven ... [Phys. Rev. B 80, 193204 (2009)] published Tue Nov 17, 2009.
Conductance distribution in doped and defected graphene nanoribbons
Antonino La Magna, Ioannis Deretzis, Giuseppe Forte, and Renato Pucci
Electronic transport at the [mu]m length scale is theoretically investigated for N-doped and vacancy damaged graphene nanoribbons. In these systems, localization due to scattering is strongly energy dependent, and this fact leads to the appearance of conductance quasigaps in the spectral region of t ... [Phys. Rev. B 80, 195413 (2009)] published Tue Nov 17, 2009.
Simultaneously optimizing the interdependent thermoelectric parameters in Ce(NiCu)Al
Peijie Sun, Tsuyoshi Ikeno, Toshio Mizushima, and Yosikazu Isikawa
Substitution of Cu for Ni in the Kondo lattice system CeNiAl results in a simultaneous optimization of the three interdependent thermoelectric parameters: thermoelectric power, electrical, and thermal conductivities, where the electronic change in conduction band induced by the extra electron of Cu ... [Phys. Rev. B 80, 193105 (2009)] published Tue Nov 17, 2009.
Local density of states of electron-crystal phases in graphene in the quantum Hall regime
O. Poplavskyy, M. O. Goerbig, and C. Morais Smith
We calculate, within a self-consistent Hartree-Fock approximation, the local density of states for different electron crystals in graphene subject to a strong magnetic field. We investigate both the Wigner crystal and bubble crystals with M electrons per lattice site. The total density of states con ... [Phys. Rev. B 80, 195414 (2009)] published Tue Nov 17, 2009.
Phonon-induced dephasing of singlet-triplet superpositions in double quantum dots without spin-orbit coupling
K. Roszak and P. Machnikowski
We show that singlet-triplet superpositions of two-electron spin states in a double quantum dot undergo a phonon-induced pure dephasing which relies only on the tunnel coupling between the dots and on the Pauli-exclusion principle. As such, this dephasing process is independent of spin-orbit couplin ... [Phys. Rev. B 80, 195315 (2009)] published Tue Nov 17, 2009.
Variable range hopping transport in ferromagnetic GaGdN epitaxial layers
A. Bedoya-Pinto, J. Malindretos, M. Roever, D. D. Mai, and A. Rizzi
Electrical-transport properties of ferromagnetic GaGdN layers grown by molecular-beam epitaxy on highly resistive 6H-SiC(0001) substrates have been investigated. It is found that doping with low concentrations of Gd increases the resistivity by several orders of magnitude as compared to unintentiona ... [Phys. Rev. B 80, 195208 (2009)] published Tue Nov 17, 2009.
Interactions between hydrogen impurities and vacancies in Mg and Al: A comparative analysis based on density functional theory
Lars Ismer, Min Sik Park, Anderson Janotti, and Chris G. Van de Walle
Using first-principles methods we have studied the interactions between hydrogen impurities and vacancies in hcp Mg and fcc Al. We find that single vacancies can, in principle, host up to 9 H atoms in Mg and 10 in Al, not 12 as recently reported in the case of Al. The difference between our results ... [Phys. Rev. B 80, 184110 (2009)] published Tue Nov 17, 2009.
Electron transport in quantum antidots made of four-terminal graphene ribbons
C. Ritter, M. Pacheco, P. Orellana, and A. Latge
Electronic and transport properties of two- and four-terminal graphene nanoribbons are studied taking into account different configurations of quantum antidot potentials, designed at a central conductor. Local density of states maps the electronic distribution changes induced by the antidot potentia ... [J. Appl. Phys. 106, 104303 (2009)] published Tue Nov 17, 2009.
Persistent photocurrent and decay studies in CdS nanorods thin films
Gouri Sankar Paul and Pratima Agarwal
Structural and electrical transport properties of thin films of CdS nanorods synthesized by solvothermal process are studied through x-ray diffraction, scanning electron microscopy, transmission electron microscopy, activation energy measurements, and decay of photoconductivity. The films show therm ... [J. Appl. Phys. 106, 103705 (2009)] published Tue Nov 17, 2009.
Monte Carlo simulation of charge transport in amorphous chalcogenides
Fabrizio Buscemi, Enrico Piccinini, Rossella Brunetti, Massimo Rudan, and Carlo Jacoboni
The most peculiar feature exhibited by the I(V) characteristics of amorphous-chalcogenide materials is undoubtedly its S-shaped behavior. This type of characteristics is very important for the technological application, e.g., in the field of nanoscale solid-state memories. In this paper we give a mi ... [J. Appl. Phys. 106, 103706 (2009)] published Tue Nov 17, 2009.
Dielectric properties of single crystalline PrO(111)/Si(111) heterostructures: Amorphous interface and electrical instabilities
O. Seifarth, Ch. Walczyk, G. Lupina, J. Dabrowski, P. Zaumseil et al.
Single crystalline PrO(111)/Si(111) heterostructures are flexible buffers for global Ge integration on Si. A combined materials scienceelectrical characterization is carried out to study the influence of postdeposition annealing in 1 bar oxygen at 300600 degrees C on the dielectric properties of Pr ... [J. Appl. Phys. 106, 104105 (2009)] published Tue Nov 17, 2009.
Enhanced response of current-driven coupled quantum wells
Antonios Balassis and Godfrey Gumbs
We have investigated the conditions necessary to achieve stronger Cherenkov-like instability of plasma waves leading to emission in the terahertz regime for semiconductor quantum wells. The surface response function is calculated for a bilayer two-dimensional electron gas (2DEG) system in the presen ... [J. Appl. Phys. 106, 103102 (2009)] published Tue Nov 17, 2009.
Using Cyclic Voltammetry to Measure Bandgap Modulation of Functionalized Carbon Nanotubes
Matthew L. Gross and Michael A. Hickner
Cyclic voltammograms of gold electrodes laden with carbon nanotubes covalently modified with various electron-withdrawing or donating moieties were measured. Carbon nanotubes modified with electron-donating bromophenyl groups showed a bandgap of 3.0 eV compared to 1.9 eV for unmodified purified tu ... [Electrochem. Solid-State Lett. 13, K5 (2009)] published Tue Nov 17, 2009.
Electric-Field-Enhanced Neutralization of Deep Centers in GaAs
D. G. Eshchenko, V. G. Storchak, S. P. Cottrell, and E. Morenzoni
The charge dynamics of hydrogenlike centers in semi-insulating GaAs have been studied by muon spin resonance in the presence of electric field and RF excitation. Electric-field-enhanced neutralization of deep electron and hole traps by track-induced hot carriers results in an increase of the excess ... [Phys. Rev. Lett. 103, 216601 (2009)] published Tue Nov 17, 2009.
Spin Conservation and Fermi Liquid near a Ferromagnetic Quantum Critical Point
Andrey V. Chubukov and Dmitrii L. Maslov
We propose a new low-energy theory for itinerant fermions near a ferromagnetic quantum critical point. We show that the full low-energy model includes, in addition to conventional interaction via spin fluctuations, another type of interaction, whose presence is crucial for the theory to satisfy SU(2 ... [Phys. Rev. Lett. 103, 216401 (2009)] published Tue Nov 17, 2009.
Local heating at a ferromagnet-metal interface
N. Neel, J. Kroger, and R. Berndt
The electronic structure of individual Co islands on Cu(111) was investigated by a cryogenic scanning tunneling microscope. An irreversible shift of the occupied Co d band toward the Fermi level was induced by elevated tunneling currents and voltages. Heating of the CoCu interface most likely induce ... [Appl. Phys. Lett. 95, 203103 (2009)] published Mon Nov 16, 2009.
Excitation of fluorescent nanoparticles by channel plasmon polaritons propagating in V-grooves
Irene Fernandez-Cuesta, Rasmus B. Nielsen, Alexandra Boltasseva, Xavier Borrise, Francesc Perez-Murano et al.
Recently, it has been proven that light can be squeezed into metallic channels with subwavelength lateral dimensions. Here, we present the study of the propagation of channel plasmon polaritons confined in gold V-grooves, filled with fluorescent particles. In this way, channel plasmon polaritons pro ... [Appl. Phys. Lett. 95, 203102 (2009)] published Mon Nov 16, 2009.
Crystalline organic superlattice
Feng Zhu, Kun Lou, Lizhen Huang, Jianbing Yang, Jidong Zhang et al.
Highly crystalline organic superlattice has great potential for providing innovative function in organic devices. With studies of the structure and fundamental electronical properties, we have demonstrated the phathalocynine organic superlattice, which is a structure composed of periodically alterna ... [Appl. Phys. Lett. 95, 203106 (2009)] published Mon Nov 16, 2009.
Charge ratchet from spin flip: Space-time symmetry paradox
Sergey Smirnov, Dario Bercioux, Milena Grifoni, and Klaus Richter
Traditionally the charge ratchet effect is considered as a consequence of either the spatial symmetry breaking engineered by asymmetric periodic potentials, or time asymmetry of the driving fields. Here we demonstrate that electrically and magnetically driven quantum dissipative systems with spin-or ... [Phys. Rev. B 80, 201310 (2009)] published Mon Nov 16, 2009.
Spin injection across the Fe/GaAs interface: Role of interfacial ordering
B. D. Schultz, N. Marom, D. Naveh, X. Lou, C. Adelmann et al.
Spin injection efficiency is shown to strongly depend on the interfacial structure between Fe contacts and AlGaAs in spin-based light emitting diodes. Both the magnitude and sign of the injected carriers are dependent on the atomic structure of the contacts and can be controlled through changes in t ... [Phys. Rev. B 80, 201309 (2009)] published Mon Nov 16, 2009.
Stacking of polycyclic aromatic hydrocarbons as prototype for graphene multilayers, studied using density functional theory augmented with a dispersion term
C. Feng, C. S. Lin, W. Fan, R. Q. Zhang, and M. A. Van Hove
The interlayer pi-pi interaction between finite-size models of graphene sheets was investigated by using a density functional theory method, augmented with an empirical R term for the description of long-range dispersive interaction; these were calibrated by studying the pi-pi interaction between va ... [J. Chem. Phys. 131, 194702 (2009)] published Mon Nov 16, 2009.
Electrical resistivity and magnetoresistance of single-crystal TbSiGe
M. Zou, V. K. Pecharsky, K. A. Gschneidner, Jr., Ya. Mudryk, D. L. Schlagel et al.
A positive colossal magnetoresistance (CMR) of 160% has been observed in TbSiGe with the magnetic field applied parallel to the a axis. When the magnetic field is applied parallel to the b and c axes, the magnetoresistance (MR) is less than 8% and 5%, respectively. The CMR effect originates from int ... [Phys. Rev. B 80, 174411 (2009)] published Mon Nov 16, 2009.
Energy relaxation probed by weak antilocalization measurements in GaN heterostructures
H. Cheng, N. Biyikli, J. Xie, C. Kurdak, and H. Morkoc
Energy relaxation and electron-phonon (e-p) interaction are investigated in wurtzite AlGaN/AlN/GaN and AlInN/AlN/GaN heterostructures with polarization induced two-dimensional electron gases in the BlochGruneisen regime. Weak antilocalization (WAL) and Shubnikovde Haas measurements were performed on ... [J. Appl. Phys. 106, 103702 (2009)] published Mon Nov 16, 2009.
Resonance terahertz detection in ungated two-dimensional electron gas
M. V. Cheremisin
The response of an ungated two-dimensional electron gas to an external electromagnetic excitation is analyzed. The possibility of creating a single-mode resonance detector operating in the terahertz frequency range is demonstrated. ... [J. Appl. Phys. 106, 104501 (2009)] published Mon Nov 16, 2009.
Enhanced thermoelectric performance by the combination of alloying and doping in TiCoSb-based half-Heusler compounds
Pengfei Qiu, Xiangyang Huang, Xihong Chen, and Lidong Chen
TiCoSb-based half-Heusler compounds have been prepared and their thermoelectric properties are studied. By isoelectronic alloying on the Ti site with Zr, although both the thermal conductivity and electrical conductivity are suppressed, the Seebeck coefficient is improved remarkably with a highest v ... [J. Appl. Phys. 106, 103703 (2009)] published Mon Nov 16, 2009.
Role of Si and Ge as impurities in ZnO
J. L. Lyons, A. Janotti, and C. G. Van de Walle
The electronic and structural properties of Si in ZnO are studied using density functional calculations with both the generalized gradient approximation and a hybrid functional. Our calculations show substitutional Si on the Zn site (Si) to be significantly lower in energy than the Si interstitial ( ... [Phys. Rev. B 80, 205113 (2009)] published Fri Nov 13, 2009.
Biexciton oscillator strength
M. Combescot and O. Betbeder-Matibet
Our goal is to provide a physical understanding of the elementary coupling between photon and biexciton and to derive the physical characteristics of the biexciton oscillator strength, following the procedure we used for trion. Instead of the more standard two-photon absorption, this work concentrat ... [Phys. Rev. B 80, 205313 (2009)] published Fri Nov 13, 2009.
Nonlinear transport theory for negative-differential resistance states of two-dimensional electron systems in strong magnetic fields
A. Kunold and M. Torres
We present a model to describe the nonlinear response to a direct dc current applied to a two-dimensional electron system in a strong magnetic field. The model is based on the solution of the von Neumann equation incorporating the exact dynamics of two-dimensional damped electrons in the presence of ... [Phys. Rev. B 80, 205314 (2009)] published Fri Nov 13, 2009.
Spin-orbit effects on the photophysical properties of Ru(bpy)
Jean-Louis Heully, Fabienne Alary, and Martial Boggio-Pasqua
We present in this article a detailed study of the photophysics of the Ru(bpy) complex based on a formalism using density functional theory and an a posteriori treatment of the spin-orbit coupling. The absorption and emission spectra were computed and a very good agreement was obtained with the avai ... [J. Chem. Phys. 131, 184308 (2009)] published Fri Nov 13, 2009.
Isolated molecular dopants in pentacene observed by scanning tunneling microscopy
Sieu D. Ha and Antoine Kahn
Doping is essential to the control of electronic structure and conductivity of semiconductor materials. Whereas doping of inorganic semiconductors is well established, doping of organic molecular semiconductors is still relatively poorly understood. Using scanning tunneling microscopy, we investigat ... [Phys. Rev. B 80, 195410 (2009)] published Fri Nov 13, 2009.
Exciton correlations in coupled quantum wells and their luminescence blue shift
B. Laikhtman and R. Rapaport
In this paper we present a study of an exciton system where electrons and holes are confined in double quantum well structures. The dominating interaction between excitons in such systems is a dipole-dipole repulsion. We show that the tail of this interaction leads to a strong correlation between ex ... [Phys. Rev. B 80, 195313 (2009)] published Fri Nov 13, 2009.
Mobius graphene strip as a topological insulator
Z. L. Guo, Z. R. Gong, H. Dong, and C. P. Sun
We study the electronic properties of the Mobius graphene strip with a zigzag edge. We show that such a graphene strip behaves as a topological insulator with a gapped bulk and a robust metallic surface, which enjoys some features due to its nontrivial topology of the spatial configuration such as t ... [Phys. Rev. B 80, 195310 (2009)] published Fri Nov 13, 2009.
Spin-polarized tunneling in fully epitaxial magnetic tunnel diodes with a narrow-gap InMnAs electrode
H. Saito, S. Yuasa, and K. Ando
We investigated spin-dependent tunneling properties in fully epitaxial Fe/ZnSe/InMnAs with a metal/insulator/semiconductor structure. A tunneling magnetoresistance (TMR) ratio up to 14% was observed, which is the first TMR reported in tunnel junctions with a narrow-gap magnetic semiconductor electro ... [Appl. Phys. Lett. 95, 192508 (2009)] published Fri Nov 13, 2009.
Mapping out the distribution of electronic states in the mobility gap of amorphous zinc tin oxide
Peter T. Erslev, Eric S. Sundholm, Rick E. Presley, David Hong, John F. Wager et al.
Amorphous zinc tin oxide (ZTO) is a wide-band-gap (transparent) semiconductor which exhibits high electron mobilities irrespective of its disordered nature. Transient photocapacitance (TPC), drive level capacitance profiling (DLCP), and modulated photocurrent spectroscopy (MPC) were used to determin ... [Appl. Phys. Lett. 95, 192115 (2009)] published Fri Nov 13, 2009.
g-factor and exchange energy in a few-electron lateral InGaAs quantum dot
M. Larsson, H. A. Nilsson, H. Hardtdegen, and H. Q. Xu
We report on the measurements of the g-factor and the exchange interaction of electrons in a few-electron lateral quantum dot formed in an InGaAs/InP semiconductor heterostructure. The spin filling sequence of the electron states in the dot is determined by magnetotransport measurements and parallel ... [Appl. Phys. Lett. 95, 192112 (2009)] published Fri Nov 13, 2009.
Disorder enhances thermoelectric figure of merit in armchair graphane nanoribbons
Xiaoxi Ni, Gengchiau Liang, Jian-Sheng Wang, and Baowen Li
We study the thermoelectric property of graphane strips by using density functional theory calculations combined with the nonequilibrium Green's function method. It is found that figure of merit (ZT) can be remarkably enhanced five times by randomly introducing hydrogen vacancies to the graphene nan ... [Appl. Phys. Lett. 95, 192114 (2009)] published Fri Nov 13, 2009.