Erratum: Two-color quark matter: U(1){sub A} restoration, superfluidity, and quarkyonic phase [Phys. Rev. D 80, 074035 (2009)]
No abstract prepared.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
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Superconductivity of incoherent electrons in the Yukawa Sachdev-Ye-Kitaev model
We study a model of N fermions in a quantum dot, coupled to M bosons by a disorder-induced complex Yukawa coupling [Yukawa Sachdev-Ye-Kitaev (SYK) model], in order to explore the interplay between non-Fermi liquid and superconductivity in a strongly coupled, (quantum-)critical environment. We analyze the phase diagram of the model for an arbitrary complex interaction and arbitrary ratio of N/M, with special focus on the two regimes of non-Fermi-liquid behavior: an SYK-like behavior with a power-law frequency dependence of the fermionic self-energy and an impuritylike behavior with frequency independent self-energy. We show that the crossover between the two can be reached by varying either the strength of the fermion-boson coupling or the ratio M/N. We next argue that in both regimes the system is unstable to superconductivity if the strength of time-reversal-symmetry-breaking disorder is below a certain threshold. We show how the corresponding onset temperatures vary between the two regimes. We argue that the superconducting state is highly unconventional with an infinite set of minima of the condensation energy at T = 0, corresponding to topologically different gap functions. We discuss in detail similarities and differences between this model and the model of dispersion-full fermions tuned to a metallic quantum-critical point, with an effective singular dynamical interaction V(Ω) ∝ 1/|Ω| γ (the γ model).
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Photonic crystals for improving light absorption in organic solar cells
We theoretically and experimentally study the structuration of organic solar cells in the shape of photonic crystal slabs. By taking advantage of the optical properties of photonic crystals slabs, we show the possibility to couple Bloch modes with very low group velocities in the active layer of the cells. These Bloch modes, also called slow Bloch modes (SBMs), allow increasing the lifetime of photons within the active layer. Finally, we present experimental demonstration performed by using nanoimprint to directly pattern the standard poly-3-hexylthiophène:[6,6]-phenyl-C61-butiryc acid methyl ester organic semiconductor blend in thin film form in the shape of a photonic crystal able to couple SBMs. In agreement with the model, optical characterizations will demonstrate significant photonic absorption gains.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Many-body interactions with single-electron quantum dots for topological quantum computation
We show that a many-body system of single-electron quantum dots, whose orbital states are dressed by a global magnetic field, can be described by an effective Hamiltonian with an anisotropic XZ spin-spin interaction which is proportional to the Zeeman splitting. We show that these interaction potentials give rise to spin-dependent Hubbard models with tunable nearest neighbor two-body and three-body interactions. The two-body interactions can even be switched off via the external electric field, and hence the three-body interaction plays a dominant role. The derivation of these effective interaction potentials follows from a well-controlled and systematic expansion into many-body interaction terms. Models of this type have appeared in the recent discussion of exotic quantum phases, in particular in the context of topological quantum phases and quantum computing, and we show that quantum dots can be regarded as a realistic experimental route which provides the basic building blocks and techniques toward the study of these phenomena. The main application of this derived model is to develop topological quantum computation.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Half-filled stripes in a hole-doped three-orbital spin-fermion model for cuprates
Using Monte Carlo techniques, we study a three-orbital CuO 2 spin-fermion model for copper-based high-critical-temperature superconductors that captures the charge-transfer properties of these compounds. Our studies reveal the presence of spin order in the parent compound and, more importantly, stripe spin and charge order under hole doping. Due to the p-d orbital hybridization, the added holes are approximately equally distributed among the two p orbitals of the oxygen atoms and the d orbital of the copper atoms in the unit cell. In rectangular clusters of dimension 16×4 half-filled stripes are observed upon hole doping; namely, when N h =2$n$ holes are introduced in the system, then n vertical stripes of length 4 along the short periodic direction are formed. The original antiferromagnetic order observed in the parent compound develops a π shift across each stripe, and the magnetic structure factor has a peak at wave vector k=(π-δ,π) with δ=2πN h /N=πN h /2L, where L=16. The electronic charge is also modulated, and the charge structure factor is maximized at $k$=(2δ,0). As electrons are removed from the system, intracell orbital nematicity with 〈$n_{p_x}$〉 -〈$n_{p_y}$〉 ≠ 0 develops in the oxygen sector, as well as intercell magnetic nematicity with 〈S$^z_{i,d}$(S$^z_{i+x,d}$-S$^z_{i+y,d}$)〉 ≠ 0 in the spin copper sector, in the standard notation. This occurs not only in rectangular but also in square 8×8 lattices. Our results suggest that the essence of the stripe spin and charge distribution experimentally observed in hole-doped cuprates is captured by unbiased Monte Carlo studies of a simple hole-doped charge-transfer insulator CuO 2 spin-fermion model.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Magnetic Properties of Eu{sub 0.9}Yb{sub 0.1}B{sub 6}
The magnetic properties of substitutional solid solutions Eu{sub 0.9}Yb{sub 0.1}B{sub 6} have been investigated in the temperature range of 2–300 K in fields up to 5 T. The data obtained confirm that the state with the electronic and magnetic phase separation (typical of europium hexaboride) is implemented in Eu{sub 0.9}Yb{sub 0.1}B{sub 6} when the system metallization (T{sub M} ≈ 15 K) precedes the ferromagnetic ordering (T{sub C} ≈ 11.4 K). An analysis of the curves M(H) in the Belov–Arrott coordinates makes it possible to evaluate spontaneous magnetization M{sub sp} and zero field susceptibility χ{sub 0} and determine the character of their critical behavior near the Curie point. The calculated critical indices (γ ≈ 1.28 and β ≈ 0.34) are in agreement with the predictions of the three-dimensional Heisenberg model.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Finite-temperature study of bosons in a two-dimensional optical lattice
We use quantum Monte Carlo (QMC) simulations to study the combined effects of harmonic confinement and temperature for bosons in a two-dimensional(2D) optical lattice. The scale-invariant, finite temperature state diagram is presented for the Bose-Hubbard model in terms of experimental parameters - the particle number, confining potential and interaction strength. To distinguish the nature of the spatially separated superfluid, Mott insulator, and normal Bose liquid phases, we examine the local density, compressibility, superfluid density, and Green's function. In the annular superfluid rings, as the width of the ring decreases, the long-range superfluid correlations start to deviate from an equivalent homogeneous 2D system. At zero temperature, the correlation decay is intermediate between one-dimension and two-dimensions, while at a finite temperature, the decay is similar to that in one-dimension at a much lower temperature. The calculations reveal shortcomings of the local density approximation in describing superfluid properties of trapped bosons. We also present the finite-temperature phase diagram for the homogeneous two dimensional Bose-Hubbard model. We compare our state diagram with the results of a recent experiment at NIST on a harmonically trapped 2D lattice [Phys. Rev. Lett. 105, 110401 (2010)], and identify a finite-temperature effect in the experiment.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
The effect of non-linear mutual friction on pulsar glitch sizes and rise times
ABSTRACT Observations of pulsar glitches have the potential to provide constraints on the dynamics of the high density interior of neutron stars. However, to do so, realistic glitch models must be constructed and compared to the data. We take a step towards this goal by testing non-linear models for the mutual friction force, which is responsible for the exchange of angular momentum between the neutron superfluid and the observable normal component in a glitch. In particular, we consider a non-linear dependence of the drag force on the relative velocity between superfluid vortices and the normal component, in which the contributions of both kelvin and phonon excitations are included. This non-linear model produces qualitatively new features, and is able to reproduce the observed bimodal distribution of glitch sizes in the pulsar population. The model also suggests that the differences in size distributions in individual pulsars may be due to the glitches being triggered in regions with different pinning strengths, as stronger pinning leads to higher vortex velocities and a qualitatively different mutual friction coupling with respect to the weak pinning case. Glitches in pulsars that appear to glitch quasi-periodically with similar sizes may thus be due to the same mechanisms as smaller events in pulsars that have no preferred glitch size, but simply originate in stronger pinning regions, possibly in the core of the star.
79 ASTRONOMY AND ASTROPHYSICS↗
Differentiating Hund from Mott physics in a three-band Hubbard-Hund model: Temperature dependence of spectral, transport, and thermodynamic properties
We study the interplay between Mott physics, driven by Coulomb repulsion U, and Hund physics, driven by Hund's coupling J, for a minimal model for Hund metals, the orbital-symmetric three-band Hubbard-Hund model (3HHM) for a lattice filling of 1/3. Hund-correlated metals are characterized by spin-orbital separation (SOS), a Hund's-rule-induced two-stage Kondo-type screening process, in which spin screening occurs at much lower energy scales than orbital screening. By contrast, in Mott-correlated metals, lying close to the phase boundary of a metal-insulator transition, the SOS window becomes negligibly small and the Hubbard bands are well separated. Using dynamical mean-field theory and the numerical renormalization group as real-frequency impurity solver, we identify numerous fingerprints distinguishing Hundness from Mottness in the temperature dependence of various physical quantities. Furthermore, These include ARPES-type spectra, the local self-energy, static local orbital and spin susceptibilities, resistivity, thermopower, and lattice and impurity entropies. Our detailed description of the behavior of these quantities within the context of a simple model Hamiltonian will be helpful for distinguishing Hundness from Mottness in experimental and theoretical studies of real materials.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Separation of continuous lines mutually overlapping and smoothed by the instrumental function
Direct and inverse spectroscopy problems concerning superposition of overlapping continuous spectral lines, as well as smoothing of the total spectrum by the instrumental function, are considered. The direct problem is formulated in two stages: initially, the total spectrum is formed by lines with a given intensity distribution, and, then, a smoothed by the spectrometer instrumental function and noisy spectrum is obtained. The inverse problem is also formulated in two stages: initially, the Fredholm integral equation of the first kind is solved by the Tikhonov regularization method (an ill-posed problem), and, then, the problem of reconstruction of separate line-component shapes from the total spectrum is solved, which is the problem of line separation (division). The individual line components are modeled by Gaussians and Lorentzians. Numerical illustrations are shown. Gaussian and dispersion (Lorentz) instrumental functions are considered.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Inhomogeneous structures in holographic superfluids. I. Dark solitons
We begin an investigation of inhomogeneous structures in holographic superfluids. As a first example, we study domain wall-like defects in the 3+1 dimensional Einstein-Maxwell-Higgs theory, which was developed as a dual model for a holographic superconductor. In [V. Keraenen, E. Keski-Vakkuri, S. Nowling, and K. P. Yogendran, Phys. Rev. D 80, 121901 (2009).], we reported on such ''dark solitons'' in holographic superfluids. In this work, we present an extensive numerical study of their properties, working in the probe limit. We construct dark solitons for two possible condensing operators and find that both of them share common features with their standard superfluid counterparts. However, both are characterized by two distinct coherence length scales (one for order parameter, one for charge condensate). We study the relative charge depletion factor and find that solitons in the two different condensates have very distinct depletion characteristics.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
V. Kozhevnikov: Thermodinamics of Magnetizing Materials and Superconductors
No abstract prepared.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Critical Properties of Perovskite Manganese Oxides Pr{sub 1−x}Ba{sub x}MnO{sub 3}
The critical properties of polycrystalline Pr{sub 1−x}Ba{sub x}MnO{sub 3} (x = 0.13 and 0.23) samples prepared by using a standard ceramic fabrication method were investigated. Pr{sub 1−x}Ba{sub x}MnO{sub 3} exhibited a second-order magnetic transition. As per the modified Arrott plot method and double logarithmic M-μ{sub 0}H curve, the critical exponents (CE) were calculated as β = 0.459 ± 0.03, γ = 1.346 ± 0.02, δ = 4.32 ± 0.04, and T{sub C} ≈ 130 K, for x = 0.13, and β = 0.424 ± 0.03, γ = 1.362 ± 0.02, δ = 4.19. ± 0.03, and T{sub C} ≈ 163 K, for x = 0.23. To confirm the reliability of such CE values, the M (H) data of Pr{sub 1−x}Ba{sub x}MnO{sub 3} were checked by the scaling equation M(H, t) = |t|{sup β}f{sub ±}(H/|t|{sup β + γ}), where t=(T/(T{sub C}))−1 refers to the reduced temperature, f{sub ±} is the scaling function above (+)/below (−) T{sub C}. The β values for Pr{sub 1−x}Ba{sub x}MnO{sub 3} (x = 0.13 and 0.23) are between β = 0.365 (3D Heisenberg exponent) and β = 0.5 (mean-field exponent), whereas γ values are fairly close to γ = 1.386. This reveals long- and short-range order coexisting in Pr{sub 1−x}Ba{sub x}MnO{sub 3}.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Study on isotropic Heisenberg interaction for the realization of SWAP {sup ±α} gates
It is known that nonlocal two-qubit gates are geometrically represented by tetrahedron called as Weyl chamber. Two edges of the Weyl chamber are formed by SWAP{sup ±α} family gates with 0 ≤ α ≤ 1. In this work SWAP{sup ±α} are being realized as two spin system with isotropic Heisenberg exchange interaction. The real parameter α is shown to be the function of duration and strength of interaction. Entanglement of the states generated by these two families of gates is studied with concurrence. Significance of time scale in realizing CNOT using SWAP{sup ±1/2} is highlighted.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Chiral interactions and superfluidity in the calcium isotopic chain
We perform ab initio calculations of three-point mass differences in the odd- and even-mass 39−49Ca isotopes to probe nuclear superfluidity via empirical neutron pairing gaps. We also quantify the sensitivity of those gaps to the parameters of the interaction at mean-field level. Recent studies employing accurate chiral nuclear interactions have found these gaps to be too small. We show that experimental values can be reproduced at mean-field level by substantially increasing the attraction of the singlet 𝑆 -wave two-nucleon contact interaction, but doing so induces an unphysical bound state of the dineutron. The sensitivity of these predictions to the full calibration of the nuclear interaction is then studied by performing Bayesian posterior sampling in a delta-full chiral effective field theory at third chiral order. We find that pairing gaps remain largely unaffected, leaving the explanation of nuclear superfluidity as a future task for improved many-body modeling and refined interactions at higher chiral orders.
Hagen, Gaute [ORNL] (ORCID:0000000160191687)↗
Density functional of a two-dimensional gas of dipolar atoms: Thomas-Fermi-Dirac treatment
We derive the density functional for the ground-state energy of a two-dimensional, spin-polarized gas of neutral fermionic atoms with magnetic-dipole interaction, in the Thomas-Fermi-Dirac approximation. For many atoms in a harmonic trap, we give analytical solutions for the single-particle spatial density and the ground-state energy, in dependence on the interaction strength, and we discuss the weak-interaction limit that is relevant for experiments. We then lift the restriction of full spin polarization and account for a time-independent inhomogeneous external magnetic field. The field strength necessary to ensure full spin polarization is derived.
74 ATOMIC AND MOLECULAR PHYSICS↗
Magnetic-field-induced nontrivial electronic state in the Kondo-lattice semimetal CeSb
Synergic effect of electronic correlation and spin-orbit coupling is an emerging topic in topological materials. Central to this rapidly developing area are the prototypes of strongly correlated heavy-fermion systems. Recently, some Ce-based compounds are proposed to host intriguing topological nature, among which the electronic properties of CeSb are still under debate. Herein, we report a comprehensive study combining magnetic and electronic transport measurements, and electronic band-structure calculations of this compound to identify its topological nature. Quantum oscillations are clearly observed in both magnetization and magnetoresistance at high fields, from which one pocket with a nontrivial Berry phase is recognized. Angular-dependent magnetoresistance shows that this pocket is elongated in nature and corresponds to the electron pocket as observed in LaBi. Nontrivial electronic structure of CeSb is further confirmed by first-principle calculations, which arises from spin splitting in the fully polarized ferromagnetic state. These features indicate that magnetic field can induce nontrivial topological electronic states in this prototypical Kondo semimetal.
36 MATERIALS SCIENCE↗
Effects of array shape and disk ellipticity in dipolar-coupled magnetic metamaterials
Not Available
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗