Energy Relations of Positron-Electron Pairs Emitted from Surfaces

Abstract

The impact of a primary positron onto a surface may lead to the emission of a correlated positron-electron pair. By means of a lab-based positron beam we studied this pair emission from various surfaces. We analyzed the energy spectra in a symmetric emission geometry. We found that the available energy is shared in an unequal manner among the partners. On average the positron carries a larger fraction of the available energy. The unequal energy sharing is a consequence of positron and electron being distinguishable particles. We provide a model which explains the experimental findings.

Positron-electron pairs emitted from metallic and oxide surfaces

“…In our previous work we demonstrated that the positronelectron pair production at surfaces leads to features in the energy distributions which are a consequence of distinguishable collision partners [10]. Specifically, we noticed that the energy sharing curves are asymmetric.…”

“…The first set was performed for normal incidence of the positron beam (θ = 0 • ). The energy distributions for this geometry was the focus of our previous study [10]. The second series was obtained with θ = ±12 • .…”

“…If a primary positron hits a surface it can lead to the emission of a positron-electron pair, we term this process as (p,ep) [9,10]. Positrons and electrons are distinguishable; hence, the interaction between them does not include exchange.…”

Fluctuation Diagnostics of the Electron Self-Energy: Origin of the Pseudogap Physics

“…This explains the lack of a consensus about the physical origin of the pseudogap: In the case of cuprates, the pseudogap has been attributed to spin fluctuations [6-10], preformed pairs [11][12][13][14][15], Mottness [16,17], and, recently, to the interplay with charge fluctuations [18][19][20][21] or to Fermi-liquid scenarios [22]. The existence and the role of (d-wave) superconducting fluctuations [11][12][13][14][15] in the pseudogap regime are still openly debated for the basic model of correlated electrons, the Hubbard model.Experimentally, the clarification of many-body physics is augmented by a simultaneous investigation at the two-particle level, i.e., via neutron scattering [23], infrared or optical [24] and pump-probe spectroscopy [25], muon-spin relaxation [26], and correlation or coincidence two-particle spectroscopies [27][28][29]. Analogously, theoretical studies of Σ can also be supplemented by a corresponding analysis at the two-particle level.…”

“…Experimentally, the clarification of many-body physics is augmented by a simultaneous investigation at the two-particle level, i.e., via neutron scattering [23], infrared or optical [24] and pump-probe spectroscopy [25], muon-spin relaxation [26], and correlation or coincidence two-particle spectroscopies [27][28][29]. Analogously, theoretical studies of Σ can also be supplemented by a corresponding analysis at the two-particle level.…”