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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

New solutions to the Dirac equation for particles in a magnetic field and a medium

We briefly review the application of the method of exact solutions of quantum equations for the description of charged particle motion in external fields. We develop a quantization technique by using the lowering and raising operators to describe the states of fermions moving in a magnetic field and a dense medium. For the first time we have posed and solved the problem of a charged fermion moving in a medium and an external magnetic field by taking into account the anomalous magnetic moment of the particle: we have obtained exact solutions for the wave functions and energy spectrum of the corresponding modified Dirac equation. We discuss a quasi-classic interpretation of the solutions obtained and, in particular, find a correction for the synchrotron radiation intensity dependent on medium density.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Large spin Seebeck effects in zigzag-edge silicene nanoribbons

Using the first-principles methods, we investigate the thermospin properties of a two-probe model based on zigzag-edge silicene nanoribbons (ZSiNRs). Compared with the odd-width ZSiNRs, the spin Seebeck coefficient of the even-width ZSiNRs is obviously enhanced at room temperature. This fact is attributed to a nearly perfect symmetry of the linear conductance gap with the different spin index with respect to the Fermi level induced by the different parity of the wave functions. More interestingly, the corresponding charge Seebeck coefficient is near zero. Therefore, when a thermal bias is presented in the even-width ZSiNRs, a nearly pure spin current is achieved. Meanwhile, the spin polarization of the current approaches infinite.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Quantum description of coupling to neutron-rearrangement channels in fusion reactions near the Coulomb barrier

The fusion cross sections for the {sup 17,18}O+{sup 27}Al, {sup 18}O+{sup 58}Ni, and {sup 6}He+{sup 197}Au reactions were calculated by the coupled-channel method. The radial dependence of matrices that describe coupling to valence-neutron-rearrangement channels was determined with the aid of two-center wave functions. The coupling-strength parameters were evaluated on the basis of numerically solving the time-dependent Schrödinger equation. Satisfactory agreement with experimental data was obtained.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Stochastic variational quantization and maximum entropy principle

In this note, we discuss the stochastic variational method (SVM) to derive the action principle of Schrödinger equation. In this formalism, the wave function is introduced as one of convenient ways to express the action. This work is a reformulation of Nelson—Yasue’s stochastic quantization scheme and its variational formulation by Yasue, and will furnish possible way to deal with more complicated system such as quantum field theory, suggesting an origin of quantum mechanics.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Atomic Systems with Bound States of Fermions in the Schwarzschild, Reissner–Nordström Fields as Candidates for the Role of Dark Matters Particles

After transition from the Dirac equation to the Schrödinger-type relativistic equation with effective potentials of the Schwarzschild and Reissner–Nordström (RN) fields, the existence of the stationary state of fermions with real square integrable radial wave functions is proved. The fermions are localized near the event horizons within the range from zero to several fractions or a few units of the Compton wavelength of a fermion as a function of both the gravitational and electromagnetic coupling constants and the angular and orbital momenta j,l. Electrically neutral atomic-type systems (Schwarzschild and RN collapsars with fermions in bound states) are proposed as particles of dark matter.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Effect of electric field on the ratio between the rashba and dresselhaus parameters in III–V heterostructures

The size-quantized energy subbands and envelope wave functions for [001] quantum wells based on zinc-blende III–V semiconductors are numerically calculated using the eight-band Kane model and finite-difference discretization scheme in coordinate space. The effect of the quantum-well band parameters and external electric field oriented along the structure growth direction on the ratio between the Rashba and Dresselhaus spin–orbit coupling parameters is studied. It is demonstrated that at certain electric-field values the spin–orbit coupling parameters in GaAs/InGaAs structures can be equal, which ensures the condition for forming stable spin helices. In addition, it is established that the spin–orbit coupling linear in wave vector in symmetric GaAs/InGaAs wells can disappear under certain well widths and barrier chemical compositions.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Quantum motion of a point particle in the presence of the Aharonov–Bohm potential in curved space

The nonrelativistic quantum dynamics of a spinless charged particle in the presence of the Aharonov–Bohm potential in curved space is considered. We chose the surface as being a cone defined by a line element in polar coordinates. The geometry of this line element establishes that the motion of the particle can occur on the surface of a cone or an anti-cone. As a consequence of the nontrivial topology of the cone and also because of two-dimensional confinement, the geometric potential should be taken into account. At first, we establish the conditions for the particle describing a circular path in such a context. Because of the presence of the geometric potential, which contains a singular term, we use the self-adjoint extension method in order to describe the dynamics in all space including the singularity. Expressions are obtained for the bound state energies and wave functions. -- Highlights: •Motion of particle under the influence of magnetic field in curved space. •Bound state for Aharonov–Bohm problem. •Particle describing a circular path. •Determination of the self-adjoint extension parameter.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Quantum electron levels in the field of a charged black hole

Stationary solutions of the Dirac equation in the metric of the charged Reissner–Nordstrom black hole are found. In the case of an extremal black hole, the normalization integral of the wave functions is finite, and the regular stationary solution is physically self-consistent. The presence of quantum electron levels under the Cauchy horizon can have an impact on the final stage of the Hawking evaporation of the black hole, as well as on the particle scattering in the field of the black hole.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

A hybrid approach for quantizing complicated motion of a charged particle in time-varying magnetic field

Quantum characteristics of a charged particle subjected to a singular oscillator potential under an external magnetic field is investigated via SU(1,1) Lie algebraic approach together with the invariant operator and the unitary transformation methods. The system we managed is somewhat complicated since we considered not only the time-variation of the effective mass of the system but also the dependence of the external magnetic field on time in an arbitrary fashion. In this case, the system is a kind of time-dependent Hamiltonian systems which require more delicate treatment when we study it. The complete wave functions are obtained without relying on the methods of perturbation and/or approximation, and the global phases of the system are identified. To promote the understanding of our development, we applied it to a particular case, assuming that the effective mass slowly varies with time under a time-dependent magnetic field.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

Effective Field Theory of Fractional Quantized Hall Nematics

We present a Landau-Ginzburg theory for a fractional quantized Hall nematic state and the transition to it from an isotropic fractional quantum Hall state. This justifies Lifshitz-Chern-Simons theory - which is shown to be its dual - on a more microscopic basis and enables us to compute a ground state wave function in the symmetry-broken phase. In such a state of matter, the Hall resistance remains quantized while the longitudinal DC resistivity due to thermally-excited quasiparticles is anisotropic. We interpret recent experiments at Landau level filling factor {nu} = 7/3 in terms of our theory.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Resonances in rotationally inelastic scattering of NH{sub 3} and ND{sub 3} with H{sub 2}

We present theoretical studies on the scattering resonances in rotationally inelastic collisions of NH{sub 3} and ND{sub 3} molecules with H{sub 2} molecules. We use the quantum close-coupling method to compute state-to-state integral and differential cross sections for the NH{sub 3}/ND{sub 3}–H{sub 2} system for collision energies between 5 and 70 cm{sup −1}, using a previously reported potential energy surface [Maret et al., Mon. Not. R. Astron. Soc. 399, 425 (2009)]. We identify the resonances as shape or Feshbach resonances. To analyze these, we use an adiabatic bender model, as well as examination at the scattering wave functions and lifetimes. The strength and width of the resonance peaks suggest that they could be observed in a crossed molecular beam experiment involving a Stark-decelerated NH{sub 3} beam.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Universal programmable quantum circuit schemes to emulate an operator

Unlike fixed designs, programmable circuit designs support an infinite number of operators. The functionality of a programmable circuit can be altered by simply changing the angle values of the rotation gates in the circuit. Here, we present a new quantum circuit design technique resulting in two general programmable circuit schemes. The circuit schemes can be used to simulate any given operator by setting the angle values in the circuit. This provides a fixed circuit design whose angles are determined from the elements of the given matrix-which can be non-unitary-in an efficient way. We also give both the classical and quantum complexity analysis for these circuits and show that the circuits require a few classical computations. For the electronic structure simulation on a quantum computer, one has to perform the following steps: prepare the initial wave function of the system; present the evolution operator U=e{sup -iHt} for a given atomic and molecular Hamiltonian H in terms of quantum gates array and apply the phase estimation algorithm to find the energy eigenvalues. Thus, in the circuit model of quantum computing for quantum chemistry, a crucial step is presenting the evolution operator for the atomic and molecular Hamiltonians in terms of quantum gate arrays. Since the presented circuit designs are independent from the matrix decomposition techniques and the global optimization processes used to find quantum circuits for a given operator, high accuracy simulations can be done for the unitary propagators of molecular Hamiltonians on quantum computers. As an example, we show how to build the circuit design for the hydrogen molecule.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Abnormal difference between the mobilities of left- and right-twisted conformations of C{sub 6}H{sub 12}N{sub 2} roto-symmetrical molecules at very low temperatures

We report an abnormal difference of low-temperature mobility of left-twisted and right-twisted conformations of roto symmetric molecules C{sub 6}H{sub 12}N{sub 2} (dabco) located in the same positions in crystal Zn{sub 2}(C{sub 8}H{sub 4}O{sub 4}){sub 2}⋅C{sub 6}H{sub 12}N{sub 2}. The difference between {sup 1}H NMR (Nuclear Magnetic Resonance) spin-relaxation data for left-twisted and right-twisted molecules reaches ∼3 × 10{sup 3} times at 8 K and tends to grow at lower temperatures. We argue that taking into account four-component relativistic Dirac wave functions in the vicinity of the nodal plane of dabco molecules and vacuum fluctuations due to virtual particle-antiparticle pairs can explain the changes which C{sub 6}H{sub 12}N{sub 2} conformations undergo at low temperatures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Relativistic description of pair production of doubly heavy baryons in e{sup +}e{sup −} annihilation

Relativistic corrections in the pair production of S-wave doubly heavy diquarks in electron-positron annihilation were calculated on the basis of perturbative QCD and the quark model. The relativistic corrections to the wave functions for quark bound states were taken into account with the aid of the Breit potential in QCD. Relativistic effects change substantially the nonrelativistic cross sections for pair diquark production. The yield of pairs of (ccq) doubly heavy baryons at B factories was estimated.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Excited States of the dtμ, pdμ, and tpμ Mesomolecules in the Variational Method

The energy spectra of excited bound states are calculated for the muonic molecules ptμ, pdμ, and dtμ on the basis of the stochastic variational method. The basis wave functions are taken as the Gaussian in shape. The matrix elements of the Hamiltonian are calculated analytically. To perform numerical calculations, computer code is written in MATLAB. Numerical values are obtained for energies of excited P states in the muonic molecules ptμ, pdμ, and dtμ.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

High-momentum components in the nuclear symmetry energy

The short-range and tensor correlations associated to realistic nucleon-nucleon interactions induce a population of high-momentum components in the nuclear many-body wave function. We study the impact of the population of such components on bulk observables associated to isospin asymmetric matter. We show how this population affects the kinetic part of the symmetry energy, which is substantially reduced with respect to the non-interacting case.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

Phase-integral method for the radial Dirac equation

A phase-integral (WKB) solution of the radial Dirac equation is calculated up to the third order of approximation, retaining perfect symmetry between the two components of the wave function and introducing no singularities except at the zeroth-order transition points. The potential is allowed to be of scalar, vector, or tensor type, or any combination of these. The connection problem is investigated in detail. Explicit formulas are given for single-turning-point phase shifts and single-well energy levels.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

Features of the electronic spectrum in a type-I core - shell quantum dot

The model is proposed, which allows one to solve the problem of finding the energy spectrum and the wave function of an electron in a type-I core - shell quantum dot. It is shown that the size of the core and shell can serve as control parameters for the optimisation of the energy structure of the quantum dot in order to obtain the real structures with desired electrophysical and optical properties. (quantum dots)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗