Hanbury Brown--Twiss interferometry with electrons: Coulomb vs. quantum statistics

Partially coherent quantum degenerate electron matter waves

“…Now take, for instance, . For the sake of comparison with reference [1] than a million times bigger than the reported value of 3 10 for the reduced counts in a continuous beam with record-high degeneracy [1]. Such notable enhancements in our signal with ultrashort pulsed electrons will enable us to have a greatly improved control of the experimental conditions in order to segregate the effects of Coulomb repulsion and electron spin.…”

“…A reduction of in the coincidence count rate of free electrons in a continuous beam emitted from a high-brightness cold field-emission tip was demonstrated. However, later analyses revealed that such small signals could have been dominated by Coulombic interactions between the free electrons in the beam casting doubt on the original claim that the direct manifestation of the PEP had been observed [2,3].…”

“…HBT-type correlations have been used to probe quantum mechanical particle statistics for various kinds of identical particles. Antibunching of thermal neutrons [13], antibunching in a Fermi gas of 40 K atoms [14], and the HBT effect for 3 He and 4 He, with the former being a fermion and the latter a boson [15], were reported about a decade ago. The HBT effect with electrons in semiconductor devices typically consisting of electron sources, drains, and mesoscopic beam splitters was observed [16][17][18].…”

“…More than a decade ago, the observation of electron degeneracy pressure for a free continuous electron beam was reported [1]. The free electron Hanbury-Brown Twiss (HBT) effect has not been repeated in other experiments and the observed defining feature, that is antibunching, has been explained by Coulomb repulsion rather than by electron quantum degeneracy in later theoretical papers [2,3]. Currently the production of degenerate free electron beams is an open problem.…”

“…In such experiments, high phasespace degeneracies, i.e. the number of electrons per phase-space cell volume [10], are available, and Coulomb repulsion between electrons is screened by space charge [3]. For free electron beams a conclusive demonstration of the HBT remains a challenge.…”