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We systematically investigate the spin-pumping effect in a series of yttrium-iron-garnet (YIG)-platinum (Pt) bilayers, comparing both broadband ferromagnetic resonance and electrically detected spin-pumping experiments. We infer the effective spin-mixing conductance as a function of YIG and Pt layer thickness from ferromagnetic resonance measurements on pure YIG layers as well as on bilayer YIG/Pt samples in a frequency range from 2 to 20 GHz. In bare YIG films, we determine a Gilbert damping constant of approximately α=0.001. With an additional platinum layer on top of the YIG samples, the damping is significantly enhanced. The effective spin-mixing conductance extracted from the ferromagnetic resonance experiments is in agreement with that determined from independent electrically detected spin-pumping experiments. [ABSTRACT FROM AUTHOR]

We report that the spin current generated by the spin Seebeck effect (SSE) in yttrium iron garnet (YIG) can be detected by a ferromagnetic metal (NiFe). By using the ferromagnetic/antiferromagnetic (FM/AFM) exchange bias structure (NiFe/IrMn), the inverse spin Hall effect (ISHE) and planar Nernst effect (PNE) of NiFe can be unambiguously separated, allowing us to observe a pure ISHE signal. After eliminating the in-plane temperature gradient in NiFe, we can even observe a pure ISHE signal without PNE from NiFe itself. It is worth noting that a large spin Hall angle (0.098) of NiFe is obtained, which is comparable with Pt. This work provides a kind of FM/AFM exchange bias structure to detect the spin current by charge signals, and highlights that ISHE in ferromagnetic metals can be used in spintronic research and applications. [ABSTRACT FROM AUTHOR]

We have investigated the vibrational properties of van der Waals heterostructures of monolayer transition metal dichalcogenides (TMDs), specifically MoS2/WSe2 and MoSe2/MoS2 heterobilayers and twisted MoS2 bilayers, by means of ultralow-frequency Raman spectroscopy. We discovered Raman features (at 30-40 cm-1) that arise from the layer-breathing mode (LBM) vibration between the two incommensurate TMD monolayers in these structures. The LBM Raman intensity correlates strongly with the suppression of photoluminescence that arises from interlayer charge transfer. The LBM is generated only in bilayer areas with direct layer-layer contact and an atomically clean interface. Its frequency also evolves systematically with the relative orientation between the two layers. Our research demonstrates that the LBM can serve as a sensitive probe to the interface environment and interlayer interactions in van der Waals materials. [ABSTRACT FROM AUTHOR]

Quantization of spin-wave excitations necessitates the reconsideration of the classical fluctuation-dissipation relation (FDR) used for temperature control in spin-lattice dynamics simulations of ferromagnetic metals. In this paper, Bose-Einstein statistics is used to reinterpret the Langevin dynamics of both lattice and spins, allowing quantum statistics to be mimicked in canonical molecular dynamics simulations. The resulting quantum heat baths are tested by calculating the specific heats and magnetization over a wide temperature range, from 0 K to above the Curie temperature, with molecular dynamics (MD), spin dynamics (SD), and spin-lattice dynamics (SLD) simulations. The results are verified with experimental data and available theoretical analysis. Comparison with classical results also shows the importance of quantization effects for spin excitations in all the ferromagnetically ordered configurations. [ABSTRACT FROM AUTHOR]

We study, theoretically and numerically, the onset and development of modulational instability in an incoherently pumped spatially homogeneous polariton condensate. Within the framework of mean-field theory, we identify regimes of modulational instability in two cases: (1) strong feedback between the condensate and reservoir, which may occur in scalar condensates, and (2) parametric scattering in the presence of polarization splitting in spinor condensates. In both cases we investigate the instability-induced textures in space and time including nonequilibrium dynamics of phase dislocations and vortices. In particular we discuss the mechanism of vortex destabilization and formation of spiraling waves. We also identify the presence of topological defects, which take the form of half-vortex pairs in the spinor case, giving an "eyelet" structure in intensity and dipole-type structure in the spin polarization. In the modulationally stable parameter domains, we observe formation of the phase defects in the process of condensate formation from an initially spatially incoherent low-density state. In analogy to the Kibble-Zurek-type scaling for nonequilibrium phase transitions, we find that the defect density scales with the pumping rate. [ABSTRACT FROM AUTHOR]

We observe a bistability in an electrically driven polariton condensate, which is manifested by a memory dependent threshold characteristic. In contrast to the polariton bistabilities previously observed in resonantly optically pumped microcavities, our effect occurs under nonresonant electric pumping and is triggered by the current injection scheme. We explain the origin of the bistability by a dependence of the electron-hole tunneling lifetime on the carrier density in the embedded quantum wells. The field screening effect creates a positive feedback loop, which yields the bistable behavior of the condensate. We develop a rate-equation-based model which qualitatively explains the occurrence of the hysteresis under current injection, its reduction with increased magnetic field, and the absence of bistability under optical pumping. [ABSTRACT FROM AUTHOR]

We introduce and model spin-Rabi oscillations based on exciton-polaritons in semiconductor microcavities. The phase and polarization of oscillations can be controlled by resonant coherent pulses and the propagation of oscillating domains gives rise to phase-dependent interference patterns in real space. We show that interbranch polariton-polariton scattering controls the propagation of oscillating domains, which can be used to realize logic gates based on an analog variable phase. [ABSTRACT FROM AUTHOR]

We consider adsorbates on metallic armchair-graphene nanoribbons (AGNRs). An adsorbed atom on a nodal site of the gapless subband in the AGNR is found to induce a bound state. The nodal-adsorbate bound state alone does not cause reflection in the AGNR quantum transport in the one propagating-channel regime. Yet its manifestation, as a Fano resonance in G, is brought forth by the presence of a non-nodal adsorbate (or a scatterer) located on a longitudinally separated site. Both the adsorbate-dependent nature and the significantly enhanced energy resolution of the Fano structure in G invite adsorbate recognition. The Fano peak is shown to be robust against weak disorder such as from edge vacancies, due to the localized nature of the Fano resonant state. Adsorbates F and OH, described within an extended Hiickel model, are considered as examples. [ABSTRACT FROM AUTHOR]

Polarized neutron scattering experiments on the slightly overdoped superconductor Ba0.5K0.5Fe2As2 reveal broad magnetic resonance scattering peaking at approximately 15 meV. In spite of doping far beyond the suppression of magnetic order, this compound exhibits dispersive and anisotropic magnetic excitations. At energies below the resonance maximum, magnetic correlations polarized parallel to the layers but perpendicular to the propagation vector are reduced by a factor of 2 compared to those in the two orthogonal directions; in contrast, correlations at the peak maximum are isotropic. [ABSTRACT FROM AUTHOR]

The crystal structure and charge and orbital order of magnetite below the Verwey temperature are calculated using a first-principles hybrid density functional theory (DFT) method. The initial atomic positions in the crystal-structure calculation are those recently refined from x-ray diffraction data for the Cc space-group unit cell [Senn, Wright, and Attfield, Nature (London) 481, 173 (2012)]. Fermi contact and magnetic dipolar contributions to hyperfine fields at 57Fe nuclei obtained from hybrid DFT calculations are used to obtain NMR resonance frequencies for magnetite for a range of external magnetic field directions in a relatively weak field. NMR frequencies from hybrid density functional theory calculations are compared to NMR data [M. Mizoguchi, J. Phys. Soc. Jpn. 70, 2333 (2001)] for a range of applied magnetic field directions. NMR resonance frequencies of B-site Fe ions show large relative variations with applied field direction owing to anisotropic hyperfine fields from charge and orbital ordered Fe 3d minority-spin electrons at those sites. Good agreement between computed and measured NMR resonance frequencies confirms the pattern of charge and orbital order obtained from calculations. The charge and orbital order of magnetite in its low-temperature phase obtained from hybrid DFT calculations is analyzed in terms of one-electron bonds between Fe ions. The Verwey transition in magnetite therefore resembles Mott-Peierls transitions in vanadium oxides which undergo symmetry-breaking transitions owing to electron-pair bond formation. [ABSTRACT FROM AUTHOR]

We use optical spectroscopy to investigate the electron-phonon interaction in Sr2IrO4, a well-known 5d transition metal oxide with spin-orbit entangled states. The temperature evolution in the optical spectra is well described by the Fröhlich polaron model, indicating a large electron-phonon interaction. We further find that electrons in different orbitals selectively couple with different phonon modes. While Jeff = 3/2 holes do not seem to couple with any phonons, Jeff = 1/2 and 3z²-r² electrons mainly couple with in-plane and out-of-plane Ir-O bending modes, respectively. The symmetries of the orbitals and phonons are consistent with our observations. [ABSTRACT FROM AUTHOR]

We report nuclear magnetic resonance (NMR) data for both the In(1) and In(2) sites in the heavy-fermion material CeRhIn5 under hydrostatic pressure. The Knight shift data reveal a suppression of the hyperfine coupling to the In(1) site as a function of pressure, and the electric field gradient ναα at the In(2) site exhibits a change of slope dναα/dP at Pc1=1.75 GPa. These changes to the coupling constants reflect alterations to the electronic structure at the quantum critical point. [ABSTRACT FROM AUTHOR]

We report on pure-quantum-state polariton condensates in optical annular traps. The study of the underlying mechanism reveals that the polariton wave function always coalesces in a single pure quantum state that, counterintuitively, is always the uppermost confined state with the highest overlap with the exciton reservoir. The tunability of such states combined with the short polariton lifetime allows for ultrafast transitions between coherent mesoscopic wave functions of distinctly different symmetries, rendering optically confined polariton condensates a promising platform for applications such as many-body quantum circuitry and continuous-variable quantum processing. [ABSTRACT FROM AUTHOR]

Spin qubits composed of either one or three electrons are realized in a quantum dot formed at a Si/SiO2 interface in isotopically enriched silicon. Using pulsed electron-spin resonance, we perform coherent control of both types of qubits, addressing them via an electric field dependent g factor. We perform randomized benchmarking and find that both qubits can be operated with high fidelity. Surprisingly, we find that the g factors of the one-electron and three-electron qubits have an approximately linear but opposite dependence as a function of the applied dc electric field. We develop a theory to explain this g-factor behavior based on the spin-valley coupling that results from the sharp interface. The outer "shell" electron in the three-electron qubit exists in the higher of the two available conduction-band valley states, in contrast with the one-electron case, where the electron is in the lower valley. We formulate a modified effective mass theory and propose that intervalley spin-flip tunneling dominates over intravalley spin flips in this system, leading to a direct correlation between the spin-orbit coupling parameters and the g factors in the two valleys. In addition to offering all-electrical tuning for single-qubit gates, the g-factor physics revealed here for one-electron and three-electron qubits offers potential opportunities for different qubit control approaches. [ABSTRACT FROM AUTHOR]

We show theoretically that an open-dissipative polariton condensate confined within a trapping potential and driven by an incoherent pumping scheme gives rise to bistability between odd and even modes of the potential. Switching from one state to the other can be controlled via incoherent pulsing which becomes an important step towards construction of low-powered optoelectronic devices. The origin of the effect comes from modulational instability between odd and even states of the trapping potential governed by the nonlinear polariton-polariton interactions. [ABSTRACT FROM AUTHOR]

A spin-spin coupling mechanism that occurs during the transport of spin-polarized minority electrons in semiconductors is described. Unlike the Coulomb spin drag, this coupling arises from the ambipolar electric field, which is created by the differential movement of the photoelectrons and the photoholes. Like the Coulomb spin drag, it is a pure spin coupling that does not affect charge diffusion. Experimentally, the coupling is studied in p+-GaAs using polarized microluminescence. The coupling manifests itself as an excitation power-dependent reduction in the spin polarization at the excitation spot without any change of the spatially averaged spin polarization. [ABSTRACT FROM AUTHOR]

In p+ GaAs thin films, the effect of photoelectron degeneracy on spin transport is investigated theoretically and experimentally by imaging the spin polarization profile as a function of distance from a tightly focused light excitation spot. Under degeneracy of the electron gas (high concentration, low temperature), a dip at the center of the polarization profile appears with a polarization maximum at a distance of about 2 μm from the center. This counterintuitive result reveals that photoelectron diffusion depends on spin, as a direct consequence of the Pauli principle. This causes a concentration dependence of the spin stiffness while the spin dependence of the mobility is found to be weak in doped material. The various effects which can modify spin transport in a degenerate electron gas under local laser excitation are considered. A comparison of the data with a numerical solution of the coupled diffusion equations reveals that ambipolar coupling with holes increases the steady-state photoelectron density at the excitation spot and therefore the amplitude of the degeneracy-induced polarization dip. Thermoelectric currents are predicted to depend on spin under degeneracy (spin Soret currents), but these currents are negligible except at very high excitation power where they play a relatively small role. Coulomb spin drag and band-gap renormalization are negligible due to electrostatic screening by the hole gas. [ABSTRACT FROM AUTHOR]

The π-plasmon dispersion in graphene was scrutinized by momentum-resolved electron energy-loss spectroscopy with an improved momentum q resolution and was found to display the square root of the q dispersion characteristic of the collective excitation of two-dimensional electron systems, in contrast to previous experimental and theoretical studies which reported a linear q dispersion. Our theoretical elaborations on the q-dependent spectra affirm this square root of q relation and further unveil an in-plane electronic anisotropy. The physical property of the π plasmon is thoroughly compared to that of the two-dimensional plasmon due to carriers of the Dirac fermions. A clear distinction between the π plasmon and the two-dimensional Dirac plasmon is demonstrated, clarifying the common notion about correlating the linearly dispersed Dirac cones with the linear dispersion of the n plasmon previously reported. [ABSTRACT FROM AUTHOR]

We study the emergence of strongly correlated states and Kondo physics in disordered graphene. Diluted short-range disorder gives rise to localized midgap states at the vicinity of the system charge neutrality point. We show that long-range disorder, ubiquitous in graphene, allows for the coupling of these localized states to an effective (disorder averaged) metallic band. The system is described by an Anderson-like model. We use the numerical renormalization group method to study the distributions of Kondo temperatures P(TK). The results show that disorder can lead to long logarithmic tails in P(TK), consistent with a quantum Griffiths phase. [ABSTRACT FROM AUTHOR]

A textured thin film of FeGe was grown by magnetron sputtering with a helimagnetic ordering temperature of TN = 276 ± 2 K. From 5 K to room temperature, a variety of scattering processes contribute toward the overall longitudinal and Hall resistivities. These were studied by combining magnetometry and magnetotransport measurements. The high-field magnetoresistance (MR) displays three clear temperature regimes: Lorentz force MR dominates at low temperatures, above T ≈80 K scattering from spin-waves predominates, while finally for T ≳ 200 K scattering from fluctuating local moments describes the MR. At low fields, where the magnetization is no longer technically saturated, we find a scaling of magnetoresistance with the square of the magnetization, indicating that the MR due to the unwinding of spins in the conical phase arises from a similar mechanism to that in magnetic domain walls. This MR is only visible up to a temperature of about 200 K. Nofeatures can be found in the temperature or field dependence of the longitudinal resistivity that belie the presence of the underlying magnetic phase transition at TN: the marked changes in behavior are at much lower temperatures. The anomalous Hall effect has a dramatic temperature dependence in which the anomalous Hall resistivity scales quadratically with the longitudinal resistivity: comparison with anomalous Hall scaling theory shows that our system is in the intrinsic "moderately dirty" regime. Lastly, we find evidence of a topological Hall effect of size ∼100 μΩ cm. [ABSTRACT FROM AUTHOR]

We report on the observation of spin whirls in a radially expanding polariton condensate formed under nonresonant optical excitation. Real space imaging of polarization- and time-resolved photoluminescence reveals a spiralling polarization pattern in the plane of the microcavity. Simulations of the spatiotemporal dynamics of a spinor condensate reveal the crucial role of polariton interactions with a spinor exciton reservoir. Harnessing spin-dependent interactions between the exciton reservoir and polariton condensates allows for the manipulation of spin currents and the realization of dynamic collective spin effects in solid-state systems. [ABSTRACT FROM AUTHOR]

Transverse magnetothermoelectric effects are studied in permalloy thin films grown on MgO substrates. We find that small parasitic magnetic fields below 1 Oe can produce artifacts of the order of 1% of the amplitude of the anisotropic magnetothermopower which is also detected in the experiments. The measured artifacts reveal a new source of uncertainties for the detection of the transverse spin Seebeck effect in conductive ferromagnets. Taking these results into account we conclude that the contribution of the transverse spin Seebeck effect in our permalloy-Pt devices to the detected voltages is below the noise level of 20 nV. [ABSTRACT FROM AUTHOR]

We investigate the influence of the interfacial Dzyaloshinskii-Moriya interaction (DMI) on the propagation of Damon-Eshbach spin waves in micrometer-sized Pt(2 nm)/Co(0.4 nm)/Py(5 nm)/MgO(5 nm) stripes. We use time-resolved scanning Kerr microscopy to image the spin waves excited by a microwave antenna and to directly access their dispersion. The presence of an interfacial DMI manifests itself in an asymmetry in the dispersion for counterpropagating spin waves which reverses sign upon reversal of the direction of the externally applied magnetic field. From this asymmetry we deduce the strength of the interfacial DMI. Micromagnetic simulations confirm that the observed difference in the wave numbers and the signature of the asymmetry are characteristic for the occurrence of an interfacial DMI at the Pt/Co interface and cannot be explained by the uniaxial perpendicular magnetic anisotropy field originating from the same interface. [ABSTRACT FROM AUTHOR]

We report detailed Knight-shift measurements of the two indium sites in the heavy-fermion compound CeIrIn5 as a function of temperature and field orientation. We find that the Knight-shift anomaly is orientation dependent, with a crossover temperature T* that varies by 50% as the field is rotated from (001) to (100). This result suggests that the hybridization between the Ce 4f states and the itinerant conduction electrons is anisotropic, a result that reflects its collective origin, and may lead to anisotropic Kondo liquid behavior and unconventional superconductivity. [ABSTRACT FROM AUTHOR]

An extensive investigation of oxidation in uranium has been pursued. This includes the utilization of soft x-ray absorption spectroscopy, hard x-ray absorption near-edge structure, resonant (hard) x-ray emission spectroscopy, cluster calculations, and a branching ratio analysis founded on atomic theory. The samples utilized were uranium dioxide (UO2), uranium trioxide (UO3), and uranium tetrafluoride (UF4). A discussion of the role of nonspherical perturbations, i.e., crystal or ligand field effects, will be presented. [ABSTRACT FROM AUTHOR]

We report on the magnetic circular dichroism of nonresonant x-ray Raman scattering. The circular dichroism has been observed at the LII,III rn edges on a pure iron sample. The observed magnetic effect is ∼2%. The dichroism spectra exhibit a significant dependence on the direction of the magnetization vector. We have constructed an effective theory to understand these behaviors. The dichroism arises from the orbital scattering and the spin scattering having different angular dependences. The calculation reproduces well the observed spectra. [ABSTRACT FROM AUTHOR]

We report measurements of the anisotropic upper critical field Hc2(T) for K2Cr3As3 single crystals up to 60 T and T>0.6K. Our results show that the upper critical field parallel to the Cr chains, H⊥c2(T), exhibits a paramagnetically limited behavior, whereas the shape of the H⊥c2(T) curve (perpendicular to the Cr chains) has no evidence of paramagnetic effects. As a result, the curves H⊥c2(T) and H‖c2(T) cross at T≈4K, so that the anisotropy parameter γH(T)=H⊥c2/H⊥c2(T) increases from γH(Tc)≈0.35 near Tc to γH(0)≈1.7 at 0.6 K. The paramagnetically limited behavior of H⊥c2(T) is inconsistent with triplet superconductivity but suggests a form of singlet superconductivity with the electron spins locked onto the direction of Cr chains. [ABSTRACT FROM AUTHOR]

We present a practical scheme for creating topological polaritons in garden-variety systems based, for example, on zinc-blende semiconductor quantum wells. Our proposal requires a moderate magnetic field and a potential landscape which can be implemented, e.g., via surface acoustic waves or patterning. We identify indirect excitons in double quantum wells as an appealing alternative for topological states in exciton-based systems. Topological polaritons and indirect excitons open a new frontier for topological states in solid-state systems, which can be directly probed and manipulated while offering a system with nonlinear interactions. [ABSTRACT FROM AUTHOR]

We report on current-induced domain wall motion in Ta/CO20Fe60B20/MgO nanowires. Domain walls are observed to move against the electron flow when no magnetic field is applied, while a field along the nanowires strongly affects the domain wall motion velocity. A symmetric effect is observed for up-down and down-up domain walls. This indicates the presence of right-handed domain walls, due to a Dzyaloshinskii-Moriya interaction (DMI) with a DMI coefficient D = +0.06 mJ/m2. The positive DMI coefficient is interpreted to be a consequence of B diffusion into the Ta buffer layer during annealing, which was observed by chemical depth profiling measurements. The experimental results are compared to one-dimensional model simulations including the effects of pinning. This modeling allows us to reproduce the experimental outcomes and reliably extract a spin-Hall angle θSH = -0.11 for Ta in the nanowires, showing the importance of an analysis that goes beyond the model for perfect nanowires. [ABSTRACT FROM AUTHOR]

The ability to discriminate between simultaneously occurring noise sources in the local environment of semiconductor InGaAs quantum dots, such as electric and magnetic field fluctuations, is key to understanding their respective dynamics and their effect on quantum dot coherence properties. We present a discriminatory approach to all-optical sensing based on two-color resonance fluorescence of a quantum dot charged with a single electron. Our measurements show that local magnetic field fluctuations due to nuclear spins in the absence of an external magnetic field are described by two correlation times, both in the microsecond regime. The nuclear spin bath dynamics show a strong dependence on the strength of resonant probing, with correlation times increasing by a factor of 4 as the optical transition is saturated. We interpret the behavior as motional averaging of both the Knight field of the resident electron spin and the hyperfine-mediated nuclear spin-spin interaction due to optically induced electron spin flips. [ABSTRACT FROM AUTHOR]

We performed a laser angle-resolved photoemission spectroscopy (ARPES) study on a wide doping range of the Ba1-xKxFe2As2 (BaK) iron-based superconductor. We observed a robust low-binding energy (BE) kink structure (kink1) in the dispersion which is doping dependent whereby its energy peaks at the optimally doped level (x ∼ 0.4) and decreases towards the underdoped and overdoped sides. We attribute this kink to electron-mode coupling in good agreement with the inelastic neutron scattering (INS) and scanning tunneling microscopy (STM) results on the same compound where a similar bosonic mode associated with spin excitations was observed. The relation between the mode energy (Ω) and the SC transition temperature (Tc) deduced from our laser ARPES data follow the universal relation deduced from INS and STM. In addition, we could resolve another kink at higher BE (kink2) showing less doping and temperature dependence compared to kink1 and which thus may be of different origin. [ABSTRACT FROM AUTHOR]

We propose a hybrid quantum architecture for engineering a photonic Mott insulator-superfluid phase transition in a two-dimensional (2D) square lattice of a superconducting transmission line resonator (TLR) coupled to a single nitrogen-vacancy (NV) center encircled by a persistent current qubit. The localization-delocalization transition results from the interplay between the on-site repulsion and the nonlocal tunneling. The phase boundary in the case of photon hopping with real-valued and complex-valued amplitudes can be obtained using the mean-field approach. Also, the quantum jump technique is employed to describe the phase diagram when the dissipative effects are considered. The unique feature of our architecture is the good tunability of effective on-site repulsion and photon-hopping rate, and the local statistical property of TLRs which can be analyzed readily using present microwave techniques. Our work opens new perspectives in quantum simulation of condensed-matter and many-body physics using a hybrid spin circuit-QED system. The experimental challenges are realizable using currently available technologies. [ABSTRACT FROM AUTHOR]

We have performed neutron diffraction measurements at 12 K on a single crystal of BaFe2As2, which serves as the parent compound of iron-based superconductors. To investigate the in-plane anisotropy of the magnetic form factor in the antiferromagnetic phase, the single crystal was detwinned. The magnetic structure factor and magnetic form factor are well explained by the spin densities comprising 3dyz electrons with a fraction of approximately 40% and electrons in the other four 3d orbitals each with a fraction of approximately 15%. It is a direct observation of the largely anisotropic spin density relative to the small orthorhombic lattice distortion, (a - b)/(a + b ) ∼ 0.3%. [ABSTRACT FROM AUTHOR]

We consider a quantum well embedded in a zero-dimensional microcavity with a subwavelength grated mirror, where the x-linearly polarized exciton mode is strongly coupled to the cavity photon, while y-polarized excitons remain in the weak-coupling regime. Under incoherent optical or electric pumping, we demonstrate polariton bistability associated with parametric scattering processes. Such bistability is useful for constructing polaritonic devices with optical or electrical incoherent pumping. [ABSTRACT FROM AUTHOR]

We have observed a magnetic vortex lattice (VL) in BaFe2(As0.67P0.33)2 (BFAP) single crystals by small-angle neutron scattering. With the field along the c axis, a nearly isotropic hexagonal VL was formed in the field range from 1 to 16 T, and no symmetry changes in the VL were observed. The temperature dependence of the VL signal was measured and confirms the presence of (non-4-wave) nodes in the superconducting gap structure for measurements at 5 T and below. The nodal effects were suppressed at high fields. At low fields, a VL reorientation transition was observed between 1 and 3 T, with the VL orientation changing by 45°. Below 1 T, the VL structure was strongly affected by pinning and the diffraction pattern had a fourfold symmetry. We suggest that this (and possibly also the VL reorientation) is due to pinning to defects aligned with the crystal structure, rather than being intrinsic. The temperature dependence of the scaled intensity suggests that BFAP possesses at least one full gap and one nodal gap with circular symmetry. Judging from the symmetry, the node structure should take the form of an "accidental" circular line node, which is consistent with recent angle-resolved photoemission spectroscopy results [ABSTRACT FROM AUTHOR]

We employ molecular beam epitaxy to stabilize Ba2IrO4 thin films and utilize in situ angle-resolved photoemission spectroscopy to investigate the evolution of its electronic structure through the Néel temperature TN. Our measurements indicate that dispersions of the relativistic Jeff = 1/2 and 3/2 bands exhibit an unusual dichotomy in their behavior through the Neel transition. Although the charge gap survives into the paramagnetic state, only the Jeff = 1/2 state exhibits a strong temperature dependence and its gap softens with increasing temperature approaching TN, while the nearly fully occupied Jeff = 3/2 state which remains nearby in energy exhibits negligible changes with temperature. [ABSTRACT FROM AUTHOR]

The magnetic, transport, and electronic properties of ultrathin epitaxial La1-xSrxMnO3 (LSMO) films at near half doping (x = 0.47, 0.50, and 0.55), grown under different misfit strains on SrTiO3(001) and La0.18Sr0.82Al0.59Ta0.41O3(001) (LSAT) substrates, are investigated. We find that all films exhibit metallic behavior below the magnetic critical temperature, while the magnetic properties change markedly with both doping and strain. However, while increased doping favors antiferromagnetic ordering, strain is the driving mechanism for the change in the magnetic properties, where with increasing tensile strain the magnetic ground state changes from ferromagnetic to antiferromagnetic at a critical lattice misfit threshold of about -1%. The bulk magnetometry data are confirmed by x-ray magnetic circular dichroism spectroscopy, while x-ray magnetic linear dichroism measured at room temperature demonstrates a progressive change in the orbital occupancy with increasing misfit strain from out of plane to in-plane, leading to a preferred antiferromagnetic metallic state at larger tensile strains. [ABSTRACT FROM AUTHOR]

We investigate the Dzyaloshinskii-Moriya interactions (DMIs) in perpendicularly magnetized thin films of Pt/Co/Pt and Pt/Co/Ir/Pt. To study the effective DMI, arising at either side of the ferromagnet, we use a fielddriven domain wall creep-based method. The use of only magnetic field removes the possibility of mixing with current-related effects such as spin Hall effect or Rashba field, as well as the complexity arising from lithographic patterning. Inserting an ultrathin layer of Ir at the top Co/Pt interface allows us to access the DMI contribution from the top Co/Pt interface. We show that the insertion of a thin Ir layer leads to reversal of the sign of the effective DMI acting on the sandwiched Co layer, and therefore continuously changes the domain wall structure from the right- to the left-handed Néel wall. The use of two DMI-active layers offers an efficient way of DMI tuning and enhancement in thin magnetic films. The comparison with an epitaxial Pt/Co/Pt multilayer sheds more light on the origin of DMI in polycrystalline Pt/Co/Pt films and demonstrates an exquisite sensitivity to the exact details of the atomic structure at the film interfaces. [ABSTRACT FROM AUTHOR]

We show that in a nonequilibrium system of an exciton-polariton condensate, where polaritons are generated from incoherent pumping, a ring-shaped pump allows for stationary vortex memory elements of topological charge m = 1 or m = - 1. Using simple potential guides we can choose whether to copy the same charge or invert it onto another spatially separate ring pump. Such manipulation of binary information opens the possibility of a new type of processing using vortices as topologically protected memory components. [ABSTRACT FROM AUTHOR]

We report a system in which the rotational, vibrational, electronic, and structural properties of condensed molecular H2 can be measured with subnanometer precision using scanning tunneling microscopy. H2 physisorbs around Ni nanoparticles on Au(111) and displays many nonclassical characteristics, including unique disappearance upon heating that is due to changes in the time-averaged phonon ground state population. This collective phenomenon also gives rise to the appearance of submolecular features and constructive overlap at points where neighboring H2 ensembles meet. A model based on the spatial distribution of collective excitations is proposed to explain these properties. [ABSTRACT FROM AUTHOR]

We have studied the anisotropy in the in-plane resistivity and the electronic structure of isovalent Ru-substituted BaFe2As2 in the antiferromagnetic-orthorhombic phase using well-annealed crystals. The anisotropy in the residual resistivity component increases in proportion to the Ru dopant concentration, as in the case of Co-doped compounds. On the other hand, both the residual resistivity and the resistivity anisotropy induced by isovalent Ru substitution are found to be 1 order of magnitude smaller than those induced by heterovalent Co substitution. Combined with angle-resolved photoemission spectroscopy results, which show almost the same anisotropic band structure for both the parent and the Ru-substituted compounds, we confirm the scenario that the anisotropy in the residual resistivity arises from anisotropic impurity scattering in the magnetostructurally ordered phase rather than directly from the anisotropic band structure of that phase. [ABSTRACT FROM AUTHOR]

Using x-ray emission spectroscopy and absorption spectroscopy, it has been possible to directly access the states in the unoccupied conduction bands that are involved with 5f and 6d covalency in oxidized uranium. By varying the oxidizing agent, the degree of 5f covalency can be manipulated and monitored, clearly and irrevocably establishing the importance of 5f covalency in the electronic structure of the key nuclear fuel, uranium dioxide. [ABSTRACT FROM AUTHOR]

We investigate spin transport through polarization-resolved spectroscopy by propagating polariton condensates in a quasi-one-dimensional microcavity ridge along macroscopic distances. Under circularly polarized, continuous-wave, nonresonant excitation, a sinusoidal precession of the spin in real space is observed whose phase depends on the emission energy. The experiments are compared with simulations of the spinor-polariton condensate dynamics based on a generalized Gross-Pitaevskii equation, modified to account for incoherent pumping, decay, and energy relaxation within the condensate. [ABSTRACT FROM AUTHOR]