Positron Annihilation and the Band Structure in Molybdenum

1972 ◽  
Vol 50 (15) ◽  
pp. 1777-1781 ◽  
Author(s):  
S. M. Kim ◽  
W. J. L. Buyers
Keyword(s):  
Wave Function ◽  
Band Structure ◽  
Angular Correlation ◽  
Room Temperature ◽  
Theoretical Calculations ◽  
Plane Waves ◽  
Interpolation Scheme ◽  
Accurate Representation ◽  
Two Photon ◽  
Positron Wave Function

Measurements have been made of the two-photon angular correlation from positrons annihilating in single-crystal molybdenum at room temperature. By means of a combination of conventional slits and Soller slits the number of annihilations for which the momentum lies along a line in the momentum distribution is obtained, and results are presented for the [ζ,ζ,0], [0,0,ζ, and [ζ,ζ,0.71] directions. Theoretical calculations of the angular correlation have been made based on the interpolation or pseudopotential scheme with s–d interaction included. The parameters of the interpolation scheme have been chosen so that an accurate representation is obtained of the APW band structure of Mattheiss. The positron wave function has been obtained in terms of 141 plane waves. The width of the calculated two-photon angular correlation is found to be much broader than the experimental width unless the relative s and d enhancement is considered.

MOMENTUM DISTRIBUTIONS OF TWO PHOTON ANNIHILATING POSITRON–ELECTRON PAIRS IN HEXANE AND DECANE

1967 ◽  
Vol 45 (12) ◽  
pp. 3895-3900 ◽  
Author(s):  
S. Y. Chuang ◽  
B. G. Hogg
Keyword(s):  
Wave Function ◽  
Positron Annihilation ◽  
Angular Correlation ◽  
High Precision ◽  
Atomic Carbon ◽  
Electron Pairs ◽  
Two Photon ◽  
Momentum Distributions ◽  
Positron Wave Function

Momentum distributions are calculated for electrons in the C–C and C–H bonds in hydrocarbons, using analytic SCF functions for atomic carbon orbitals and Heitler–London-type functions for the two paired electrons in the C–C and C–H bonds. The positron wave function is assumed to be a constant. The computed momentum distributions are then compared with high-precision experimental distributions obtained from positron-annihilation angular correlation experiments.

scholarly journals Finite-temperature violation of the anomalous transverse Wiedemann-Franz law

2020 ◽  
Vol 6 (17) ◽  
pp. eaaz3522 ◽  
Author(s):  
Liangcai Xu ◽  
Xiaokang Li ◽  
Xiufang Lu ◽  
Clément Collignon ◽  
Huixia Fu ◽  
...  
Keyword(s):  
Wave Function ◽  
Inelastic Scattering ◽  
Finite Temperature ◽  
Room Temperature ◽  
Theoretical Calculations ◽  
Data Accuracy ◽  
Berry Curvature ◽  
Curvature Distribution ◽  
Open Question ◽  
Transverse Response

The Wiedemann-Franz (WF) law has been tested in numerous solids, but the extent of its relevance to the anomalous transverse transport and the topological nature of the wave function, remains an open question. Here, we present a study of anomalous transverse response in the noncollinear antiferromagnet Mn3Ge extended from room temperature down to sub-kelvin temperature and find that the anomalous Lorenz ratio remains close to the Sommerfeld value up to 100 K but not above. The finite-temperature violation of the WF correlation is caused by a mismatch between the thermal and electrical summations of the Berry curvature and not by inelastic scattering. This interpretation is backed by our theoretical calculations, which reveals a competition between the temperature and the Berry curvature distribution. The data accuracy is supported by verifying the anomalous Bridgman relation. The anomalous Lorenz ratio is thus an extremely sensitive probe of the Berry spectrum of a solid.

scholarly journals Massless Composite Bosons Formed by the Coupled Electron-Positron Pairs and Two-Photon Angular Correlations in the Colliding Beam Reaction e-e+→Bγγ with Emission of the Massless Boson

2018 ◽  
Vol 2018 ◽  
pp. 1-18 ◽  
Author(s):  
A. I. Agafonov
Keyword(s):  
Wave Function ◽  
Free Particle ◽  
Plane Waves ◽  
Wave Functions ◽  
Two Photon ◽  
Electron Positron ◽  
Correlation Spectrum ◽  
Composite Bosons ◽  
Massless Boson ◽  
Colliding Beams

The approach in which the electron and positron are treated as ordinary, different particles, each being characterized by the complete set of the Dirac plane waves, is examined. This completely symmetric representation that is beyond the standard QED makes it necessary to choose another solution of the Dirac equation for the free particle propagator as compared to that used currently. The Bethe-Salpeter equation with these particle propagators is solved in the ladder approximation. A new solution has been found represented by the massless composite bosons formed by the coupled electron-positron pairs with the coupling equal to the fine structure constant. It has been demonstrated that (1) the massless boson states have normalizable complex wave functions which are transversely compressed plane waves; (2) the transverse radius of the wave functions diverges as the boson energy goes to zero; that is, the composite bosons cannot be at rest; (3) increasing the boson energy results in an extension of the transverse wave function in the momentum space and a corresponding contraction of the real space coordinate wave function. The new reaction e-e+→Bγγ is investigated with the products composed of the massless composite boson and two photons. The cross-section of this reaction is derived for nonrelativistic colliding beams of spin-polarized electrons and positrons. In this case the 2γ angular correlation spectrum is characterized by a narrow peak with the full-width-at-half-maximum not exceeding 0.2 mrad. It is shown that in order to distinguish between the conventional annihilation of the singlet electron-positron pair with the two-photon emission and the new examined reaction yielding the three particles, experiments are proposed with the extremely nonrelativistic colliding beams.

An experimental and theoretical study of the momentum distribution of two photon annihilating positron–electron pairs in methane

1968 ◽  
Vol 46 (20) ◽  
pp. 2309-2313 ◽  
Author(s):  
S. Y. Chuang ◽  
W. H. Holt ◽  
B. G. Hogg
Keyword(s):  
Wave Function ◽  
Ground State ◽  
Theoretical Study ◽  
Experimental Distribution ◽  
Electron Pairs ◽  
Two Photon ◽  
Momentum Plane ◽  
Radial Schrödinger Equation ◽  
Momentum Distributions ◽  
Positron Wave Function

The momentum distributions of annihilating positron–electron pairs have been measured in liquid and solid methane. Calculated momentum distributions generally assume that the positron wave function ψ+ = 1. This low-momentum, plane-wave representation of the positron is inadequate to describe the experimental distribution for high momenta. A ψ+ obtained by numerical integration of the ground-state radial Schrödinger equation is employed in the calculation and a good fit is observed with experiment for all momentum values.

Angular correlation of two-photon positron annihilation in hydrogen gas

1979 ◽  
Vol 57 (7) ◽  
pp. 1027-1030 ◽  
Author(s):  
J. W. Darewych
Keyword(s):  
Wave Function ◽  
Angular Correlation ◽  
Molecular Hydrogen ◽  
Hydrogen Gas ◽  
Annihilation Radiation ◽  
Annihilation Rate ◽  
Two Photon ◽  
State Approximation ◽  
The One ◽  
Photon Annihilation

The expression for the angular correlation of two-photon annihilation radiation for positrons colliding with molecular hydrogen is derived. The one-state approximation is used, and a one-centre expansion of the hydrogen wave function is assumed. Results obtained using a simple H2 wave function yield a half-width of the angular distribution which is in agreement with the observed results for positrons annihilating in liquid hydrogen. Comparison is made with corresponding results for the annihilation rate.

scholarly journals Nonreciprocal charge transport up to room temperature in bulk Rashba semiconductor α-GeTe

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yan Li ◽  
Yang Li ◽  
Peng Li ◽  
Bin Fang ◽  
Xu Yang ◽  
...  
Keyword(s):  
Charge Transport ◽  
Room Temperature ◽  
Theoretical Calculations ◽  
Ferromagnetic Layer ◽  
Spin Splitting ◽  
New Paradigm ◽  
Rashba Spin ◽  
Rashba Spin Splitting ◽  
Fundamental Insight ◽  
Insight Into

AbstractNonmagnetic Rashba systems with broken inversion symmetry are expected to exhibit nonreciprocal charge transport, a new paradigm of unidirectional magnetoresistance in the absence of ferromagnetic layer. So far, most work on nonreciprocal transport has been solely limited to cryogenic temperatures, which is a major obstacle for exploiting the room-temperature two-terminal devices based on such a nonreciprocal response. Here, we report a nonreciprocal charge transport behavior up to room temperature in semiconductor α-GeTe with coexisting the surface and bulk Rashba states. The combination of the band structure measurements and theoretical calculations strongly suggest that the nonreciprocal response is ascribed to the giant bulk Rashba spin splitting rather than the surface Rashba states. Remarkably, we find that the magnitude of the nonreciprocal response shows an unexpected non-monotonical dependence on temperature. The extended theoretical model based on the second-order spin–orbit coupled magnetotransport enables us to establish the correlation between the nonlinear magnetoresistance and the spin textures in the Rashba system. Our findings offer significant fundamental insight into the physics underlying the nonreciprocity and may pave a route for future rectification devices.

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