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The surface spin states for bismuth thin films are investigated using an sp³ tight-binding model. The model explains most experimental observations using angle-resolved photoemission spectroscopy, including the Fermi surface, the band structure with Rashba spin splitting, and the quantum confinement in the energy band gap of the surface states. A large out-of-plane spin component also appears. The surface states penetrate inside the film to within approximately a few bilayers near the Brillouin-zone center, whereas they reach the center of the film near the Brillouin-zone boundary. [ABSTRACT FROM AUTHOR]

In epitaxial thin films of magnetite a large change in magnetization across the Verwey transition has been observed. In the Verwey state, the sample magnetization appeared to be strongly reduced, in some samples even close to zero. Using superconducting quantum interference magnetometry, x-ray absorption near edge spectroscopy, and polarized neutron reflectometry, a simple rotation of the magnetization vector due to a change in magnetocrystalline anisotropy was excluded. The experimental data rather suggest an intrinsic loss ofmagnetic moment due to a possible transition into a low or intermediate spin state of Fe2+. This observation discloses a different aspect of the Verwey transition. [ABSTRACT FROM AUTHOR]

We study the complex spin-state switching mechanism in a bistable molecular crystal undergoing a stepwise conversion from high-spin to low-spin states at thermal equilibrium as well as during the relaxation process from the photoinduced metastable state.We experimentally evidence that such steps are associated with complex types of long-range and short-range ordering phenomena, resulting from the occupational modulation of bistable molecular magnetic states. The conversion is then described by using two order parameters: the totally symmetric average high spin fraction and the symmetry breaking ordering parameter. The use of the anisotropic next-nearestneighbor Ising (ANNNI) model allows us to describe the microscopic origin of the ordering, and Monte Carlo simulations reproduce the observed stepwise thermal phase transition as well as the stepwise relaxation from the photoinduced high-spin state to the low-spin state. [ABSTRACT FROM AUTHOR]

We propose a protocol to preserve the spin state of rare-earth ions when they are optically cycled. This technique uses large magnetic fields to increase the probability of an optically excited ion returning to its initial spin state. This Zeeman enhanced cyclicity is shown to be applicable to non-Kramers ions in various crystals irrespective of the site symmetry. The specific example of Pr3+:Y2SiO5 is investigated to demonstrate that the protocol can create closed optical transitions even where the point group symmetry of the site is C1. In this example, the predicted cyclicity exceeds 104. This high level of cyclicity extends the usefulness of rare-earth ion crystals for applications in quantum and classical information processing. We explore the use of this technique to enable single-ion, spin-state optical readout and the creation of ensemble-based spectral features that are robust against optical cycling. [ABSTRACT FROM AUTHOR]

Low-spin states in the neutron-rich, N = 90 nuclide 146Ba were populated following β decay of 146Cs, with the goal of clarifying the development of deformation in barium isotopes through delineation of their nonyrast structures. Fission fragments of 146Cs were extracted from a 1.7-Ci 252Cf source and mass selected using the CAlifornium Rare Ion Breeder Upgrade (CARIBU) facility. Low-energy ions were deposited at the center of a box of thin β detectors, surrounded by a highly efficient high-purity Ge array. The new 146Ba decay scheme now contains 31 excited levels extending up to ∼2.5 MeV excitation energy, double what was previously known. These data are compared to predictions from the interacting boson approximation (IBA) model. It appears that the abrupt shape change found at N = 90 in Sm and Gd is much more gradual in Ba and Ce, due to an enhanced role of the γ degree of freedom. [ABSTRACT FROM AUTHOR]

In this paper we study the number of states with given spin for identical particles, denoted as DIn(l) for bosons and as DIn(j) for fermions, where I is the total angular momentum of the system, n is the particle number, l is the spin of a single boson, and j is the spin of a single fermion. We derive relations of DIn(l) and DIn(j); in particular, we obtain recursive and explicit formulas of DIn(l) and DIn(j) in terms of those for n - 1 particles and apply them to systems of two, three, and five identical particles. [ABSTRACT FROM AUTHOR]

We propose a versatile and efficient method to generate a broad class of complex entangled states of many atoms via the detection of a single photon. For an atomic ensemble contained in a strongly coupled optical cavity illuminated by weak single- or multifrequency light, the atom-light interaction entangles the frequency spectrum of a transmitted photon with the collective spin of the atomic ensemble. Simple time-resolved detection of the transmitted photon then projects the atomic ensemble into a desired pure entangled state. This method can be implemented with existing technology, yields high success probability per trial, and can generate complex entangled states such as mesoscopic superposition states of coherent spin states with high fidelity. [ABSTRACT FROM AUTHOR]

A series of high-pressure measurements including resistivity, ac and dc magnetic susceptibility, neutron powder diffraction, and synchrotron x-ray diffraction were performed to investigate the crystal structure and electronic states of the itinerant ferromagnet SrCoO3. Two pressure-induced phase transitions were observed at about 1.1 and 45 GPa, corresponding to a spin reorientation and a spin-state transition, respectively, while the cubic crystal structure was stable with pressure up to 60.0 GPa. The origins of these electronic state changes are discussed and rationalized in the light of first-principles calculations. [ABSTRACT FROM AUTHOR]

We have investigated the lattice distortion coupled to the Co 3d-spin-state ordering in thin films of perovskite LaCoO3 with various epitaxial strains by measurements of the magnetization, x-ray diffraction, and optical spectra. In the system with tensile strain about 0.5%, a lattice distortion characterized by the modulation vector q=(1/6,1/6,1/6) emerges at 40 K, followed by a ferromagnetic ordering at 24 K. Alternatively, in systems with tensile strain exceeding 1%, the lattice distortion characterized by q=(1/4,1/4,1/4) emerges at 120 K or higher, and subsequently the ferromagnetic or ferrimagnetic ordering occurs around 90 K. The evolution of infrared phonon spectra and resonant x-ray scattering at the Co K edge suggests that the population change in the Co 3d spin state causes the strain-induced switching of spin-state ordering as well as of magnetic ordering in this canonical spin-state crossover system. [ABSTRACT FROM AUTHOR]

Anisotropic magnetoresistance measurements show that the magnetization state in epitaxial Ni80Fe20/Fe50Mn50 bilayers exhibits aging over a wide range of temperatures and magnetic fields. The observed power-law time dependence indicates that aging is characterized by a wide range of activation time scales. Aging characteristics are also inconsistent with a superposition of independent activation barriers expected for Arrhenius-type relaxation. The observed effects indicate a fundamental connection with the critical phenomena in complex condensed matter systems. [ABSTRACT FROM AUTHOR]

Background: The high-momentum distribution of atoms in two spin-state ultracold atomic gases with strong short-range interactions between atoms with different spins, which can be described by using Tan's contact, are dominated by short-range pairs of different fermions and decreases as k-4. In atomic nuclei the momentum distribution of nucleons above the Fermi momentum (k > kF ≈ 250 MeV/c) is also dominated by short-range-correlated different-fermion (neutron-proton) pairs. Purpose: Compare high-momentum unlike-fermion momentum distributions in atomic and nuclear systems. Methods: We show that, for k > kF MeV/c, nuclear momentum distributions are proportional to that of the deuteron. We then examine the deuteron momentum distributions derived from a wide variety of modern nucleon-nucleon potentials that are consistent with NN-scattering data. Results: The high-momentum tail of the deuteron momentum distribution, and hence of the nuclear momentum distributions, appears to decrease as k-4. This behavior is shown to arise from the effects of the tensor part of the nucleon-nucleon potential. In addition, when the dimensionless interaction strength for the atomic system is chosen to be similar to that of atomic nuclei, the probability for finding a short-range different-fermion pair in both systems is the same. Conclusions: Although nuclei do not satisfy all of the conditions for Tan's contact, the observed similarity of the magnitude and k-4 shape of nuclear and atomic momentum distributions is remarkable because these systems differ by about 20 orders of magnitude in density. This similarity may lead to a greater understanding of nuclei and the density dependence of nuclear systems. [ABSTRACT FROM AUTHOR]

We report the first beyond-mean-field study of low-lying parity-doublet states in 224Ra by extending the multireference relativistic energy density functional method to include dynamical correlations related to symmetry restoration and quadrupole-octupole shape fluctuation with a generator coordinate method combined with parity, particle-number, and angular-momentum projections. We clarify microscopically that the origin of spin-dependent parity splitting in low-spin states is related to the octupole shape stabilization of positive-parity states, the shapes of which drift gradually toward those of negative-parity ones. [ABSTRACT FROM AUTHOR]

Interactions between two excitons can result in the formation of bound quasiparticles, known as biexcitons. Their properties are determined by the constituent excitons, with orbital and spin states resembling those of atoms. Monolayer transition metal dichalcogenides (TMDs) present a unique system where excitons acquire a new degree of freedom, the valley pseudospin, from which a novel intervalley biexciton can be created. These biexcitons comprise two excitons from different valleys, which are distinct from biexcitons in conventional semiconductors and have no direct analog in atomic and molecular systems. However, their valley properties are not accessible to traditional transport and optical measurements. Here, we report the observation of intervalley biexcitons in the monolayer TMD MoS2 using ultrafast pump-probe spectroscopy. By applying broadband probe pulses with different helicities, we identify two species of intervalley biexcitons with large binding energies of 60 and 40 meV. In addition, we also reveal effects beyond biexcitonic pairwise interactions in which the exciton energy redshifts at increasing exciton densities, indicating the presence of many-body interactions among them. [ABSTRACT FROM AUTHOR]

Electronic spin systems with S > 1/2 provide an efficient method for dc vector magnetometry, since the conventional electron spin resonance spectra at a given magnetic field reflect not only the field strength but also orientation in the presence of strong spin-spin interactions. S = 1 spins, e.g., the nitrogen-vacancy centers in diamond, have been intensively investigated for such a purpose. In this report, we compare S = 1 and 3/2 spins, and discuss how one can apply general principles for the use of high-spin systems as a vector magnetometer to the S = 3/2 spin systems. We find analytical solutions which allow a reconstruction of the magnetic field strength and polar angle using the observed resonance transitions if a uniaxial symmetry exists for the spin-spin interaction as in S = 1 systems. We also find that an ambiguity of determining the field parameters may arise due to the unique properties of S = 3/2 systems, and present solutions for it utilizing additional transitions in the low-field region. The electronic spins of the silicon vacancy in silicon carbide will be introduced as a model for the S = 3/2 dc vector magnetometer and the practical usage of it, including the magic-angle spinning type method, will be presented too. [ABSTRACT FROM AUTHOR]

We present a continuous-time Monte Carlo impurity solver for multiorbital impurity models which combines a strong-coupling hybridization expansion and a weak-coupling expansion in the Hund's coupling parameter J. This double-expansion approach allows to treat the dominant density-density interactions U within the efficient segment representation. We test the approach for a two-orbital model with static interactions, and then explain how the double expansion allows to simulate models with frequency dependent U(ω) and J(ω). The method is used to investigate spin-state transitions in a toy model for fullerides, with repulsive bare J but attractive screened J. [ABSTRACT FROM AUTHOR]

In the search for the fully aligned 27- state in 140Nd predicted by cranked Nilsson-Strutinsky calculations, new close-to-spherical high-spin states have been discovered. Both the close-to-spherical and the triaxial calculated states are in good agreement with the experimental results, supporting the existence of shape coexistence up to very high spins. Shell-model calculations using a newly developed effective interaction for the 50 ≤ N,Z ≤ 82 mass region are in good agreement with the observed spherical states. The comparison between the experimental and calculated level energies allowed the relative energy to be established between several proton and neutron orbitals at high energy and spins. [ABSTRACT FROM AUTHOR]

We studied experimentally the dynamics of the exchange interaction between two antiparallel electron spins in an isolated double quantum dot where coupling to the electron reservoirs can be ignored. We demonstrate that the level of control of such a double dot is higher than in conventional double dots. In particular, it allows us to couple coherently two electron spins in an efficient manner following a scheme initially proposed by Loss and DiVincenzo [Phys. Rev. A 57, 120 (1998)]. The present study demonstrates that isolated quantum dots are a possible route to increase the number of coherently coupled quantum dots. [ABSTRACT FROM AUTHOR]

All-optical addressing and coherent control of single solid-state based quantum bits is a key tool for fast and precise control of ground-state spin qubits. So far, all-optical addressing of qubits was demonstrated only in a very few systems, such as color centers and quantum dots. Here, we perform high-resolution spectroscopic of native and implanted single rare earth ions in solid, namely, a cerium ion in yttrium aluminum garnet (YAG) crystal. We find narrow and spectrally stable optical transitions between the spin sublevels of the ground and excited optical states. Utilizing these transitions we demonstrate the generation of a coherent dark state in electron spin sublevels of a single Ce3+ ion in YAG by coherent population trapping. [ABSTRACT FROM AUTHOR]

We investigate the transport of excitations through a chain of atoms with nonlocal dissipation introduced through coupling to additional short-lived states. The system is described by an effective spin-1/2 model where the ratio of the exchange interaction strength to the reservoir coupling strength determines the type of transport, including coherent exciton motion, incoherent hopping, and a regime in which an emergent length scale leads to a preferred hopping distance far beyond nearest neighbors. For multiple impurities, the dissipation gives rise to strong nearest-neighbor correlations and entanglement. These results highlight the importance of nontrivial dissipation, correlations, and many-body effects in recent experiments on the dipole-mediated transport of Rydberg excitations. [ABSTRACT FROM AUTHOR]

We report a new measurement of the midrapidity inclusive jet longitudinal double-spin asymmetry, ALL, in polarized pp collisions at center-of-mass energy √s=200??GeV. The STAR data place stringent constraints on polarized parton distribution functions extracted at next-to-leading order from global analyses of inclusive deep-inelastic scattering (DIS), semi-inclusive DIS, and RHIC pp data. The measured asymmetries provide evidence at the 3s level for positive gluon polarization in the Bjorken-x region x>0.05. [ABSTRACT FROM AUTHOR]

We employ a combination of the ab initio band-structuremethods and dynamical mean-field theory to determine the electronic structure and phase stability of paramagnetic FeO at high pressure and temperature. Our results reveal a high-spin to low-spin transition within the B1 crystal structure of FeO upon compression of the lattice volume above 73 GPa. The spin-state transition is accompanied by an orbital-selective Mott metal-insulator transition (MIT). The lattice volume is found to collapse by about 8.5% at theMIT, implying a complex interplay between electronic and lattice degrees of freedom. Our results for the electronic structure and lattice properties are in overall good agreement with experimental data. [ABSTRACT FROM AUTHOR]

We present photoluminescence studies of CdTe and Cd1-xMnxTe quantum dots grown in two adjacent layers. We show that when the dots are 8 nm apart, their magneto-optical properties--Zeeman shifts and transition linewidths--are analogous to those of individual CdTe or Cd1-xMnxTe dots. When the dots are grown closer, at a distance of 4 nm, it becomes possible to tune the electron states to resonance and obtain a formation of a molecular state hybridized over the two dots. As a result of the resonant enhancement of the electron-Mn ion exchange interaction, spectroscopic signatures specific to spin-dependent interdot coupling appear. Namely, an anomalous increase of the Zeeman shift and a resonant increase in the transition linewidth are observed. A simple model calculation allows us to quantitatively reproduce the experimental results. [ABSTRACT FROM AUTHOR]

Superconducting quantum interference devices (SQUIDs) and other superconducting circuits are limited by intrinsic flux noise with spectral density 1/fα with α<1 whose origin is believed to be due to spin impurities. Here, we present a theory of flux noise that takes into account the vectorial nature of the coupling of spins to superconducting wires. We present explicit numerical calculations of the flux-noise power (spectral density integrated over all frequencies) for electron impurities and lattice nuclear spins under several different assumptions. The noise power is shown to be dominated by surface electron spins near the wire edges, with bulk lattice nuclear spins contributing ~5% of the noise power in aluminum and niobium wires. We consider the role of electron spin phase transitions, showing that the spin-spin correlation length (describing, e.g., the average size of ferromagnetic spin clusters) greatly impacts the scaling of flux noise with wire geometry. Remarkably, the flux-noise power is exactly equal to zero when the spins are polarized along the flux-vector direction, forming what we call a poloidal state. Flux noise is nonzero for other spin textures, but gets reduced in the presence of correlated ferromagnetic fluctuations between the top and bottom wire surfaces, where the flux vectors are antiparallel. This demonstrates that engineering spin textures and/or intersurface correlation provides a method to reduce flux noise in superconducting devices. [ABSTRACT FROM AUTHOR]

Quantum measurement is a combination of a read-out and a perturbation of the quantum system. We explore the nonlinear spin dynamics generated by a linearly polarized probe beam in a continuous measurement of the collective spin state in a thermal alkali-metal atomic sample. We demonstrate that the probe-beam-driven perturbation leads, in the presence of indirect pumping, to complete polarization of the sample and macroscopic coherent spin oscillations. As a consequence of the former we report observation of spectral profiles free from collisional broadening. Nonlinear dynamics is studied through exploring its effect on radiofrequency as well as spin noise spectra. [ABSTRACT FROM AUTHOR]

Combining scanning tunneling microscopy and first-principles calculations, we have shown that single Co atoms adsorbed on a Si(111)-(7 × 7) surface have eight different configurations that possess different spin magnetic moments. Despite the large adsorption energy, we have demonstrated that both the position and the spin state of single adsorbed Co atoms can be well controlled through the vertical atomic manipulation and the "tip-touch" operation that converts Co atoms among various adsorption configurations. Our approach to construct atomic-scale magnetic structures on a semiconductor surface can provide a new pathway to realize spin-based devices, including a scalable solid-state quantum computer. [ABSTRACT FROM AUTHOR]

Efficient readout of individual electronic spins associated with atomlike impurities in the solid state is essential for applications in quantum information processing and quantum metrology. We demonstrate a new method for efficient spin readout of nitrogen-vacancy (NV) centers in diamond. The method is based on conversion of the electronic spin state of the NV to a charge-state distribution, followed by single-shot readout of the charge state. Conversion is achieved through a spin-dependent photoionization process in diamond at room temperature. Using NVs in nanofabricated diamond beams, we demonstrate that the resulting spin readout noise is within a factor of 3 of the spin projection noise level. Applications of this technique for nanoscale magnetic sensing are discussed. [ABSTRACT FROM AUTHOR]

Strong laser fields can be used to trigger an ultrafast molecular response that involves electronic excitation and ionization dynamics. Here, we report on the experimental control of the spatial localization of the electronic excitation in the C60 fullerene exerted by an intense few-cycle (4 fs) pulse at 720 nm. The control is achieved by tailoring the carrier-envelope phase and the polarization of the laser pulse. We find that the maxima and minima of the photoemission-asymmetry parameter along the laser-polarization axis are synchronized with the localization of the coherent electronic wave packet at around the time of ionization. [ABSTRACT FROM AUTHOR]

The purpose of this article is to derive the analytic expression for the angular-momentum dependence (I dependence) of the moment of inertia in microscopic mean-field theory for both even-even and odd-mass nuclei. Based on the constrained Hartree-Fock-Bogoliubov theory, the Coriolis antipairing effect is taken into account as the second-order perturbation to the BCS basis together with the blocking effect. Instead of integration, an asymptotic series expansion is applied to the quantity in which finiteness of the nuclear system becomes tangible in the high-spin region, where the gap parameter Δ becomes much smaller than the average single-particle level distance d. As a result, Δ keeps a small but finite value even for high-spin states, showing that there is no sharp phase transition in the nucleus. Analytic formulas are derived for the / dependence of the moment of inertia for different regions of Δ ≥ d/2 and Δ < d/2. [ABSTRACT FROM AUTHOR]

The excited states of the 20Ne nucleus from the ground state to Ex = 25 MeV were investigated with the 22Ne(p,t)20Ne reaction at a beam energy of Ep = 60 MeV using the QDD magnetic spectrometer at iThemba LABS. Narrow, low-spin Jπ = 0+, l-, and 2+ states have been observed for the first time at high-excitation energies in 20Ne, namely at Ex = 17.67, 18.84, 20.59, 21.16, 21.80, and 22.5 MeV. Shell-model and coupled reaction channel calculations were performed to determine the nature of the newly observed states. Candidates for T - 2 states are proposed at 3.86(5), 4.43(5) MeV and 5.07(5) MeV above the lowest 0+, T = 2 state at Ex = 16.73 MeV. Two of these T = 2 candidates appear to result from core excitations in the Op shell. The state at Ex = 22.5 MeV, which could not be interpreted by the shell-model calculations, is a tentative candidate for the 5-α cluster state. [ABSTRACT FROM AUTHOR]

Based on the Bardeen-Cooper-Schrieffer theory of superconductivity, the coherent splitting of Cooper pairs from a superconductor to two spatially separated quantum dots has been predicted to generate nonlocal pairs of entangled electrons. In order to test this hypothesis, we propose a scheme to transfer the spin state of a split Cooper pair onto the polarization state of a pair of optical photons. We show that the photon pairs produced can be used to violate a Bell inequality, unambiguously demonstrating the entanglement of the split Cooper pairs. [ABSTRACT FROM AUTHOR]

Reversible magnetic exchange springs can be formed in the magnetically soft YFe2 layers of epitaxial DyFe2/YFe2 multilayer films. Here we show that the insertion of just two monolayers of DyFe2, placed directly in the middle of the YFe2 layers, brings about substantial changes. Results are presented for a Dy-doped (110)-oriented [DyFe2(60Å)/YFe2(120Å)/DyFe2(8Å)/YFe2(120Å)]15 multilayer film, measured at 100 K in fields of up to ±10 T. Using bulk magnetometry, micromagnetic modeling, and Dy-specific x-ray magnetic circular dichroism, it is shown that Dy doping substantially increases the number of spin states available to the system. Altogether 12 distinct spring states are identified which bring additional complexity to the magnetic reversal process. In particular, the exchange springs are no longer reversible, exhibiting magnetic exchange-spring collapse. Full and partial magnetic loops are presented for fields applied along the in-plane easy [001] axis and the in-plane hard [110] axis. In particular, it is demonstrated that exchange-spring collapse is sharpest when the field is applied along a hard in-plane [110] axis. [ABSTRACT FROM AUTHOR]

Negative parity high-spin states of 107Cd have been investigated using the reaction 94Zr(18O,5n), from the γ-ray coincidence events recorded by the Indian National Gamma Array. A magnetic dipole (M1) band structure was established for the first time in this nucleus decaying to the low-spin states via several paths. Lifetimes of five in-band levels in this band have been measured using the Doppler shift attenuation method. The experimentally deduced B(M1) values are found to decrease with increasing spin. The experimental observations, interpreted by the tilted axis cranking calculations, suggest that the M1 band is developed from the shears mechanism based on the 5qp configuration π(g9/2-2) ⊗ ν(h11/2g7/2²), which is then crossed by another 5qp configuration π(g9/2-2) ⊗ ν(h11/2³). The semiclassical model of the shears mechanism also reasonably reproduces the decreasing trend of the observed B(M1) values as a function of spin, supporting the above interpretation. The present work highlights the unique coexistence of both magnetic and antimagnetic (observed by us earlier) rotation bands in one nucleus arising from the same proton configuration, but different neutron configurations. [ABSTRACT FROM AUTHOR]

The issue of the existence of reflection asymmetry in 145Ba has stood for the past 30 years without a common conclusion. The recent experimental data show a number of low-lying rotational bands with alternative parities, providing more strict constraints on the relevant modeling. With a proper octupole deformation, all the observed six rotational bands in 145Ba have been well reproduced by the reflection asymmetric shell model (RASM). The three octupole deformed neutron single-particle orbitals just above the octupole shell gap 88, with K = 1/2, K = 3/2, and K = 5/2, respectively, dominate the intrinsic configurations of the observed bands. Based on the analysis of the calculated RASM wave functions, the assignments for the observed bands have been given. The experimental yrast band (ΔI = 1) presents a simplex inversion at around the 11/2- state where the simplex staggering phase changes. This phenomenon may be explained in the framework of the RASM as from the change of the dominate intrinsic configuration, induced by the band mixing. The present results strongly support the appearance of the reflection asymmetry in the ground and low-lying states of 145Ba. [ABSTRACT FROM AUTHOR]

Spin impurities in diamond can be versatile tools for a wide range of solid-state-based quantum technologies, but finding spin impurities that offer sufficient quality in both photonic and spin properties remains a challenge for this pursuit. The silicon-vacancy center has recently attracted much interest because of its spin-accessible optical transitions and the quality of its optical spectrum. Complementing these properties, spin coherence is essential for the suitability of this center as a spin-photon quantum interface. Here, we report all-optical generation of coherent superpositions of spin states in the ground state of a negatively charged silicon-vacancy center using coherent population trapping. Our measurements reveal a characteristic spin coherence time, T*2, exceeding 45 nanoseconds at 4 K. We further investigate the role of phonon-mediated coupling between orbital states as a source of irreversible decoherence. Our results indicate the feasibility of all-optical coherent control of silicon-vacancy spins using ultrafast laser pulses. [ABSTRACT FROM AUTHOR]

The silicon-vacancy (SiV-) color center in diamond has attracted attention because of its unique optical properties. It exhibits spectral stability and indistinguishability that facilitate efficient generation of photons capable of demonstrating quantum interference. Here we show optical initialization and readout of electronic spin in a single SiV- center with a spin relaxation time of T1=2.4±0.2 ms. Coherent population trapping (CPT) is used to demonstrate coherent preparation of dark superposition states with a spin coherence time of T*1=35±3 ns. This is fundamentally limited by orbital relaxation, and an understanding of this process opens the way to extend coherence by engineering interactions with phonons. Hyperfine structure is observed in CPT measurements with the 29Si isotope which allows access to nuclear spin. These results establish the SiV- center as a solid-state spin-photon interface. [ABSTRACT FROM AUTHOR]

We present a light-matter interface which consists of a single 174Yb+ ion coupled to an optical fiber cavity. We observe that photons at 935 nm are mainly emitted into the cavity mode and that correlations between the polarization of the photon and the spin state of the ion are preserved despite the intrinsic coupling into a single-mode fiber. Complementary, when a faint coherent light field is injected into the cavity mode, we find enhanced and polarization dependent absorption by the ion. [ABSTRACT FROM AUTHOR]

We report electrical transport measurements in a tilted magnetic field on a high-mobility two-dimensional electron system (2DES) confined at the MgZnO/ZnO heterointerface. The observation of multiple crossing events of spin-resolved Landau levels (LLs) enables the mapping of the sequence of electronic states. We further measure the renormalization of electron spin susceptibility at zero field and the susceptibility dependence on the electron spin polarization. The latter manifests the deviation from the Pauli spin susceptibility. As a result, the crossing of spin-resolved LLs shifts to smaller tilt angles and the first Landau level coincidence event is absent even when the magnetic field has only a component perpendicular to the 2DES plane. [ABSTRACT FROM AUTHOR]

Nitrogen-vacancy centers in diamond (NV) attract great attention because they serve as a tool in many important applications. The NV center has a polarizable spin S=1 ground state and its spin state can be addressed by optically detected magnetic resonance (ODMR) techniques. The mS=0 and mS=±1 spin levels of the ground state are separated by about 2.88 GHz in the absence of an external magnetic field or any other perturbations. This zero-field splitting (ZFS) can be probed by ODMR. As this splitting changes as a function of pressure and temperature, the NV center might be employed as a sensor operating at the nanoscale. Therefore, it is of high importance to understand the intricate details of the pressure and temperature dependence of this splitting. Here we present an ab initio theory of the ZFS of the NV center as a function of external pressure and temperature including detailed analysis on the contributions of macroscopic and microscopic effects. We found that the pressure dependence is governed by the change in the distance between spins as a consequence of the global compression and the additional local structural relaxation. The local structural relaxation contributes to the change of ZFS with the same magnitude as the global compression. In the case of temperature dependence of ZFS, we investigated the effect of macroscopic thermal expansion as well as the consequent change of the microscopic equilibrium positions. We could conclude that theses effects are responsible for about 15% of the observed decrease of ZFS. [ABSTRACT FROM AUTHOR]

We use a combination of dynamical mean-field model calculations and LDA + U material specific calculations to investigate the low temperature phase transition in the compounds from the (Pr1-yRy)xCa1-xCoO3 (R=Nd,Sm,Eu,Gd,Tb,Y) family (PCCO). The transition, marked by a sharp peak in the specific heat, leads to an exponential increase of dc resistivity and a drop of the magnetic susceptibility, but no order parameter has been identified yet. We show that condensation of spin-triplet, atomic-size excitons provides a consistent explanation of the observed physics. In particular, it explains the exchange splitting on the Pr sites and the simultaneous Pr valence transition. The excitonic condensation in PCCO is an example of a general behavior expected in certain systems in the proximity of a spin-state transition. [ABSTRACT FROM AUTHOR]

Magnetic order and excitations in multiferroic DyMnO3 were studied by neutron scattering experiments using a single crystal prepared with an enriched 162Dy isotope. The ordering of Mn moments exhibits pronounced hysteresis arising from the interplay between Mn and Dy magnetism, which has a strong impact on the ferroelectric polarization. The magnon dispersion resembles that reported for TbMnO3. We identify the excitations at the magnetic zone center and near the zone boundary in the b direction, which can possess electromagnon character. The lowest frequency of the zone-center magnons is in good agreement with a signal in a recent optical measurement, so this mode can be identified as the electromagnon coupled by the same Dzyaloshinskii-Moriya interaction as the static multiferroic phase. [ABSTRACT FROM AUTHOR]

Spin-cluster excitations induced by microwave radiation have been detected as a function of an applied magnetic field in the rare-earth kagome system Nd3Ga5SiO14. The results are interpreted using a Heisenberg model which allows for anisotropic exchange interactions between neighboring spins. At a microwave frequency of 120 GHz the conventional independent-ion electron spin resonance (ESR) spectrum, due to Zeeman splitting of the ground state Kramers doublet, is not observed at low temperatures. Instead, a large number of resonances are seen that are shifted from the conventional ESR position. These resonances persist to temperatures well above 20 K with similar behavior found at 230 GHz. The observations are consistent with the excitation of spin waves in short-range antiferromagnetically correlated spin loops or clusters and are similar to the ESR spectral features seen previously in the Pr3Ga5SiO14 kagome system. Upon increasing the temperature and/or the microwave frequency, a broad Zeeman resonance does eventually emerge at the predicted ground state doublet resonance field. [ABSTRACT FROM AUTHOR]

We report experimental studies of dressing an electron spin in diamond with resonant and continuous microwave fields to protect the electron spin from magnetic fluctuations induced by the nuclear spin bath. We use optical coherent population trapping (CPT) to probe the energy level structure, optically induced spin transitions, and spin decoherence rates of the dressed spin states. Dressing an electron spin with resonant microwaves at a coupling rate near 1 MHz leads to a 50 times reduction in the linewidth of the spin transition underlying the CPT process, limited by transit-time broadening. Compared with dynamical decoupling, where effects of the bath are averaged out at specific times, the dressed spin state provides a continuous protection from decoherence. [ABSTRACT FROM AUTHOR]

High-spin states in the doubly-odd 198Bi nucleus have been studied by using the 185,187Re(16O,xn) reactions at a beam energy of 112.5 MeV. β-β coincidences, directional correlation ratio, and integrated polarization asymmetry ratio were measured by using the INGA array with 15 Compton-suppressed clover high-purity germanium (HPGe) detectors. Definite spins and parities were assigned to the observed levels. The high-spin structure is grouped into three bands (B1, B2, and B3), of which two (B1 and B2) exhibit the properties of magnetic rotation (MR). Tilted axis cranking calculations were carried out to explain the MR bands having large multiquasiparticle (qp) configurations. The calculated results explain the bands B1 and B2 very nicely, confirming the shears mechanism and suggest a crossing of two MR bands in both the cases. The crossing is from 6-qp to 8-qp in band B1 and from 4-qp to 6-qp in band B2, a very rare finding. A semiclassical model has also been used to obtain the particle-hole interaction strengths below the band crossing for the bands B1 and B2. [ABSTRACT FROM AUTHOR]

A study of the 4α linear-chain structure in high-lying collective excitation states of 16O with covariant density functional theory is presented. The low-spin states are obtained by configuration mixing of particle-number and angular-momentum projected quadrupole deformed mean-field states with the generator coordinate method. The high-spin states are determined by cranking calculations. These two calculations are based on the same energy density functional PC-PK1. We have found a rotational band at low spin with the dominant intrinsic configuration considered to be the one whereby 4α clusters stay along a common axis. The strongly deformed rod shape also appears in the high-spin region with the angular momentum 13ħ to 18ħ; however, whether the state is a pure 4α linear chain is less obvious than for the low-spin states. [ABSTRACT FROM AUTHOR]

We investigate a novel method of accurate calculation of the neutrinoless double-β decay shell-model nuclear matrix elements for the experimentally relevant case of 76Ge. We demonstrate that with the new method the nuclear matrix elements have perfect convergence properties and, using only the first 100 intermediate states of each spin, the matrix elements can be calculated with better than 1% accuracy. Based on the analysis of neutrinoless double-β decays of 48Ca,82Se, and 76Ge isotopes, we propose a new method to estimate the optimal values of the average closure energies at which the closure approximation gives the most accurate nuclear matrix elements. We also analyze the nuclear matrix elements for the heavy-neutrino-exchange mechanism, and we show that our method can be used to quench contributions from different intermediate spin states. [ABSTRACT FROM AUTHOR]

The recoil-β tagging technique was used to identify transitions associated with the decay of the 2+ and, tentatively, the 4+ excited states in 74Sr. Combining these results with published data for the A = 74 isobars, triplet energy differences (TEDs) have been extracted, the heaviest case for which these values have been evaluated. State-of-the-art shell-model calculations using the JUN45 interaction and incorporating a J = 0 isospin nonconserving (INC) interaction with an isotensor strength of 100 keV can reproduce the trend in the TED data, with particularly good agreement for the 2+ state. This agreement for the TED data taken together with the fact that agreement has also been shown between shell-model calculations with the same strength of INC interaction in the f7/2 shell and recently for A = 66 strongly suggests that such an interaction exists throughout the nuclear chart and cannot have a strong dependence on details of nuclear structure such as which nuclear orbitals are occupied. It also supports the hypothesis that only a J = 0 component of the INC interaction need be included to explain the observed TEDs. [ABSTRACT FROM AUTHOR]

High spin states in neutron-rich l47Ce have been reinvestigated by measuring the triple- and fourfold γ-γ coincidence data observed in the spontaneous fission of 252Cf. The positive-parity band is expanded to spin (45/2) h and the negative-parity side band is expanded to spin (39/2) with a new third band connected to it. An octupole band structure with s = +/ was proposed. The systematic characteristics of the octupole correlations have been discussed. Reflection asymmetric shell model calculations for the octupole band structure of l47Ce are in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Coherent electron-spin dynamics in Ga1-xMnxN has been investigated by time-resolved Kerr rotation spectroscopy. The effective electron g factor shows a linear increase with the Mn concentration due to the s-d exchange coupling between the conduction electrons and the d-shell electrons of Mn3+ impurities. The magnitude and sign of the s-d exchange constant are determined precisely to be N0α = +0.23 ± 0.02 eV, indicative of a ferromagnetic s-d exchange coupling in GaMnN. The determined N0α is consistent with the typical value found in most diluted magnetic semiconductors and reveals that GaMnN is indeed not an exception. [ABSTRACT FROM AUTHOR]

We propose a method to create "spin cat states," i.e., macroscopic superpositions of coherent spin states, in Bose-Einstein condensates using the Kerr nonlinearity due to atomic collisions. Based on a detailed study of atom loss, we conclude that cat sizes of hundreds of atoms should be realistic. The existence of the spin cat states can be demonstrated by optical readout. Our analysis also includes the effects of higher-order nonlinearities, atom number fluctuations, and limited readout efficiency. [ABSTRACT FROM AUTHOR]