共查询到20条相似文献,搜索用时 31 毫秒
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《Physics letters. A》2020,384(28):126745
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《Physics letters. A》2019,383(19):2333-2338
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BN-AlN alloys are potential candidates to achieve wide band gap material for ultraviolet device applications. By combing density functional theory and evolutionary structure predictions, we systematically explore the thermodynamic, mechanical, dynamical and optical properties of alloys. Through structure search, three compounds (cubic (, and , space group P-43m), and tetragonal (, space group P-42m)) have been predicted. The calculated relative large formation enthalpies suggest that large miscibility gap exists in BAlN alloys. In addition, computed elastic constants and phonon show that these structures are mechanically and dynamically stable. From the state of the art LDA-1/2 we show that the direct band gap of BN-AlN evinces strong deviation from a linear dependence on B composition. We found -in particular- giant direct band gap bowing parameter of eV for the entire range of composition, where b parameter is found to be sensitive to composition x. From a detailed analysis of the physical origin of the optical gap bowing b, we found that structural and chemical contributions play the most significant effects behind the huge optical band gap bowing parameter of BAlN alloys. 相似文献
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S. Nazir 《Physics letters. A》2019,383(16):1977-1982
Interfacial magnetism and magnetic anisotropy constant () in Co/MgO heterostructure have been studied using ab-initio density functional calculations. It is found that interfacial Co spin magnetic moment shows a strong interdependence on Co-O bond lengths and a reasonable spin-polarization of ~80% is established as a function of Co layers. Our results revealed a saturated positive (out-of-plane) of +2.80 mJ/m2 at ≥12 Co layers (~1.6 nm Co thickness), which is associated with orbital magnetic moment difference in [100] and [001] direction along with a strong hybridization between and orbitals through orbital angular momentum operator . Furthermore, it is shown that the magnitude almost remains constant and weakens in the case of under- and over-oxidations in the interfacial MgO and Co layers, respectively. Interestingly, improved for oxygen migrated interface due to enhanced and orbitals coupling. The disordered interfaces stability is checked by analyzing the formation energy. Hence, the present findings disclose that the higher Co thickness in ordered Co/MgO structure supports to out-of-plane [001] (positive) , which could be useful for its technological implementation in high-density magnetic data storage devices with high thermal stability. 相似文献
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J.E. Hirsch 《Physics letters. A》2019,383(1):83-90
We find that the bulk moment of inertia per unit volume of a metal becoming superconducting increases by the amount , with the bare electron mass and the classical electron radius. This is because superfluid electrons acquire an intrinsic moment of inertia , with the London penetration depth. As a consequence, we predict that when a rotating long cylinder becomes superconducting its angular velocity does not change, contrary to the prediction of conventional BCS-London theory that it will rotate faster. We explain the dynamics of magnetic field generation when a rotating normal metal becomes superconducting. 相似文献
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Ferdinand Grüneis 《Physics letters. A》2019,383(13):1401-1409
Single quantum dots and other materials exhibit irregular switching between on and off states; these on–off states follow power-law statistics giving rise to 1/f noise. We transfer this phenomenon (also referred to as on–off intermittency) to the generation and recombination (= g–r) process in semiconductor materials. In addition to g–r noise we obtain 1/f noise that can be provided in the form of Hooge's relation. The predicted Hooge coefficient is whereby depends on the parameters of the g–r noise and on the parameters of the intermittency. Due to the power-law distribution of the on-times, the coefficient shows a smooth dependence on time t. We also suggest an alternative form of Hooge's 1/f noise formula relating the 1/f noise to the number of centers (such as donor or trap atoms) rather than to the number of charge carriers as defined by Hooge. 相似文献
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We investigate the Glauber divergences in nonfactorizable annihilation amplitudes for two-body hadronic heavy meson decays in the factorization theorem at one-loop level. These divergences can be absorbed into the Glauber factors in the dominant kinematic regions of small parton momenta, which modify the interference between a nonfactorizable annihilation amplitude and other amplitudes by rotating it with a phase. We postulate that only the Glauber effect associated with a pion is significant, due to its special role as a bound state and as a pseudo Nambu–Goldstone boson simultaneously. It is elaborated that the data of the and branching ratios have revealed prominent Glauber effects. This work provides a solid theoretical ground for the factorization-assisted topological-amplitude parametrization of two-body hadronic meson decays. 相似文献
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《Physics letters. A》2020,384(14):126281
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With the help of the nonequilibrium Green's function technique, we theoretically analyze the thermospin property through a typical T-shaped spin valve with spin-flip scattering in the linear regime. The influences of spin-flip coefficient of interdot λ, spin-flip coefficient of intradot η and interdot hopping coefficient on thermospin property are discussed. As interdot hopping coefficient t is equal to energy level ε, the spectrum of shows Fano-like effect with ε variation. Antiresonance position of is almost unchanged and its width becomes narrower with ε increasing. Spin thermopower is close to the maximum of the peak and charge thermopower is equal to zero for . As a result, the pure spin thermopower can be obtained, which means that a pure spin current may be produced by a temperature gradient in our system. It is found that spin figure of merit can reach a considerable value by adjusting key parameters of the system, such as Δt, β, α, ?. The typical T-shaped spin valve can be treated as a stable thermospin battery which allows to convert the heat energy to spin voltage, thus produces the pure spin current in the device. 相似文献
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《Physics letters. A》2020,384(36):126930
We consider quantum bosons with contact interactions at the Lowest Landau Level (LLL) of a two-dimensional isotropic harmonic trap. At linear order in the coupling parameter g, we construct a large, explicit family of quantum states with energies of the form , where and are integers. Any superposition of these states evolves periodically with a period of until, at much longer time scales of order , corrections to the energies of order may become relevant. These quantum states provide a counterpart to the known time-periodic behaviors of the corresponding classical (mean field) theory. 相似文献