We report on the charging behavior of a single self-assembled InGaAs quantum dot with unpolarized and spin-polarized electrons under direct current (DC) and high-frequency biasing. The tunnel coupling of the quantum dot to a spin-polarized electron reservoir leads to characteristic voltage dependenc...

[Phys. Rev. B 85, 035325] Published Tue Jan 31, 2012

A gas of ultracold ⁶Li atoms (effective spin 1/2) confined to an elongated trap with one-dimensional properties is a candidate to display three different phases: (i) fermions bound in Cooper-pair-like states, (ii) unbound spin-polarized particles, and (iii) a mixed phase in which Cooper bound states...

[Phys. Rev. B 85, 024535] Published Mon Jan 30, 2012

Recent spin-Seebeck experiments on thin ferromagnetic films apply a temperature difference ΔT_x along the length x and measure a (transverse) voltage difference ΔV_y along the width y. The connection between these involves: (1) thermal equilibration between sample and substrate, (2) spin currents alon...

[Phys. Rev. B 85, 035446] Published Mon Jan 30, 2012

We report on a topological Hall effect possibly induced by scalar spin chirality in a quasi-two-dimensional helimagnet Fe_1+δSb. In the low-temperature region where the spins on interstitial-Fe (concentration δ∼0.3) intervening the 120° spin-ordered triangular planes tend to freeze, a nontrivial comp...

[Phys. Rev. Lett. 108, 056601] Published Mon Jan 30, 2012

We study Josephson-like junctions formed by materials with antiferromagnetic (AF) order parameters. As an antiferromagnet, we consider a two-band material in which a spin density wave (SDW) arises. This could be Fe-based pnictides in the temperature interval T_c≤T≤T_N, where T_c and T_N are the critical...

[Phys. Rev. B 85, 014523] Published Fri Jan 27, 2012

We study the shot noise (nonequilibrium current fluctuation) associated with dynamic nuclear polarization in a nonequilibrium quantum wire (QW) fabricated in a two-dimensional electron gas. We observe that the spin-polarized conductance quantization of the QW in the integer quantum Hall regime colla...

[Phys. Rev. B 85, 041309] Published Thu Jan 26, 2012

Oblique deposition conditions of Si were used to create a periodic compositional defect matrix in Fe₃Si/MgO(001) thin films. The modified growth conditions provoke shadow effects, which lead to a two-magnon scattering channel with twofold symmetry in the film plane. Its axis is controlled by the sam...

[Phys. Rev. B 85, 014420] Published Thu Jan 19, 2012

The effect of a longitudinal magnetic field on the optical spin orientation and spin-dependent recombination in dilute nitrides GaAsN has been studied for the first time. We have found that intensity I and circular polarization degree ρ of the edge photoluminescence, excited in GaAsN alloys by circu...

[Phys. Rev. B 85, 035205] Published Tue Jan 17, 2012

Topological insulators are insulating in the bulk but possess metallic surface states protected by time-reversal symmetry. Here, we report on a detailed electronic transport study in high-quality Bi₂Se₃ topological insulator thin films contacted by superconducting (In, Al, and W) electrodes. The res...

[Phys. Rev. B 85, 045415] Published Tue Jan 10, 2012

The possibility of manipulating the tunneling magnetoresistance (TMR) of antiferromagnetic nanostructures is predicted in the framework of ab initio calculations. By the example of a junction composed of an antiferromagnetic dimer and a spin-polarized scanning tunneling microscopy tip we show that t...

[Phys. Rev. B 85, 045406] Published Thu Jan 05, 2012

Spin crossover by means of an electric bias is investigated by spin-polarized density-functional theory calculations combined with the Keldysh nonequilibrium Green’s technique in a molecular junction, where an individual single-molecule magnet Fe₂(acpybutO)(O₂CMe)(NCS)₂ is sandwiched between two inf...

[Phys. Rev. Lett. 108, 017202] Published Thu Jan 05, 2012

We demonstrate coherent optical control of a single hole spin confined to an InAs/GaAs quantum dot. A superposition of hole-spin states is created by fast (10–100 ps) dissociation of a spin-polarized electron-hole pair. Full control of the hole spin is achieved by combining coherent rotations about ...

[Phys. Rev. Lett. 108, 017402] Published Thu Jan 05, 2012

Graphite, a model (semi)metal with trigonally warped bands, is investigated with a magnetoabsorption experiment and viewed as an electronic system in the vicinity of the Lifshitz transition. A characteristic pattern of up to 20 cyclotron resonance harmonics has been observed. This large number of re...

[Phys. Rev. Lett. 108, 017602] Published Wed Jan 04, 2012

We identify the Dresselhaus spin-orbit coupling as the source of the dominant spin-relaxation mechanism in the impurity band of a wide class of n-doped zinc blende semiconductors. The Dresselhaus hopping terms are derived and incorporated into a tight-binding model of impurity sites, and they are sh...

[Phys. Rev. Lett. 108, 016601] Published Tue Jan 03, 2012

Hole spin relaxation and intervalley electron scattering in bulk Ge at 300 K are distinguished and selectively investigated using a spectrally, temporally, and polarization-resolved pump-probe differential transmission technique that takes advantage of the indirect band gap nature of Ge and of the d...

[Phys. Rev. B 84, 214307] Published Wed Dec 28, 2011

We describe a nonlinear interaction between charge currents and spin currents which arises from the energy dependence of the conductivity. This allows nonmagnetic contacts to be used for measuring and controlling spin signals. We choose graphene as a model system to study these effects and predict i...

[Phys. Rev. B 84, 241408] Published Tue Dec 27, 2011

We analyze the equilibrium frequency-dependent spin current noise and spin conductance through a quantum dot in the local moment regime. Spin current correlations behave markedly differently from charge correlations. Equilibrium spin correlations are characterized by two universal scaling functions ...

[Phys. Rev. B 84, 235441] Published Tue Dec 27, 2011

The magnetic moment and spin-polarized electron transport properties of triangular graphene flakes surrounded by boron nitride sheets (BNC structures) are studied by first-principles calculation based on density functional theory. Their dependence on the BNC structure is discussed, revealing that sm...

[Phys. Rev. B 84, 224424] Published Wed Dec 21, 2011

We consider a model for an edge state of electronic systems in the quantum Hall regime with filling ν=1 and in the quantum spin Hall regime. In both cases, the system is in contact with two reservoirs by tunneling at point contacts. Both systems are locally driven by applying an ac voltage in one of...

[Phys. Rev. B 84, 235436] Published Wed Dec 21, 2011

We study a two-dimensional electron system in the presence of spin-orbit interaction. It is shown analytically that the spin-orbit interaction acts as a transversal effective electric field, whose orientation depends on the sign of the ẑ-axis spin projection. This effect does not require any drivin...

[Phys. Rev. Lett. 107, 266801] Published Mon Dec 19, 2011

One of the primary objectives in molecular nanospintronics is to manipulate the spin states of organic molecules with a d-electron center, by suitable external means. In this Letter, we demonstrate by first principles density functional calculations, as well as second order perturbation theory, that...

[Phys. Rev. Lett. 107, 257202] Published Thu Dec 15, 2011

Spin scattering at the interface formed between metallic Fe and Cu-phthalocyanine molecules is investigated by spin-polarized scanning tunneling spectroscopy and spin-resolved photoemission. The results are interpreted using first-principles electronic structure theory. The combination of experiment...

[Phys. Rev. B 84, 224403] Published Fri Dec 09, 2011

The charge transport of serially coupled quantum dots (SCQD) connected to the metallic electrodes is theoretically investigated in the Coulomb blockade regime. A closed-form expression for the tunneling current of SCQD in the weak interdot hopping limit is obtained by solving an extended two-site Hu...

[Phys. Rev. B 84, 245303] Published Fri Dec 09, 2011

We report an experimental method to estimate the bias dependence of the perpendicular spin torque in magnetic tunnel junctions. This method utilizes the pulse-width-dependent change in the switching phase diagram and addresses the perpendicular-torque-driven precessional switching at high-bias range...

[Phys. Rev. B 84, 214417] Published Fri Dec 09, 2011

We theoretically investigate spin-resolved currents flowing in large-area graphene, with and without defects, doped with single atoms of noble metals (Cu, Ag, and Au) and 3d-transition metals (Mn, Fe, Co, and Ni). We show that the presence of a local magnetic moment is a necessary but not sufficient...

[Phys. Rev. B 84, 245411] Published Fri Dec 09, 2011

Using an empirical pseudopotential description of electron states and an adiabatic bond charge model for phonon states in bulk silicon, we theoretically investigate two-photon indirect optical injection of carriers and spins and two-color coherent control of the motion of the injected carriers and s...

[Phys. Rev. B 84, 235204] Published Tue Dec 06, 2011

[Phys. Rev. Lett. 107, 249901] Published Tue Dec 06, 2011

We show a spin superconductor in ferromagnetic graphene as the counterpart to the charge superconductor in which a spin-polarized electron-hole pair plays the role of the spin 2(ℏ/2) “Cooper pair” with a neutral charge. We present a BCS-type theory for the spin superconductor. With the “London-type ...

[Phys. Rev. B 84, 214501] Published Fri Dec 02, 2011

We report ab initio pseudopotential DFT calculations on the energetic stability and magnetic ordering of Cr in diamond at various lattice sites and charge states and show that Cr is most stable at the divacancy site in diamond, with the lowest formation energy occurring in n- or p-type diamond, comp...

[Phys. Rev. B 84, 235201] Published Thu Dec 01, 2011

We study the electronic transport through a noncollinear single-electron spin-valve transistor. It consists of a small metallic island weakly coupled to two ferromagnetic leads with noncollinear magnetization directions. The electric current is influenced by Coulomb charging and by spin accumulation...

[Phys. Rev. B 84, 235409] Published Thu Dec 01, 2011