10 am PST / 11 am MST / 1 pm EST

ROOM: 301 PSB  Zoom: https://cornell.zoom.us/j/373862927 Password: CBB

Single electron emitters, plasmonic bullseyes, and the search for coherent electrons

I will discuss several projects related to electron sources including (1) Efforts to develop a “single electron source” based on an optical single photon source that could emit electrons sequentially, reducing charge interactions in electron optical systems.

(2) Use of cathodoluminescence spectral imaging to optimize plasmonic photoemission from “bullseye” cathodes by “time-inversion”. These antennas are designed to emit electrons when excited by radially-polarized laser pulses. We used electrons to locally excite the resonant structures and detected optical radiation in the far field [1].

(3) Electron imaging methods including TEM, SEM and STM generate images by averaging over many single electrons. Diffraction processes arise from an electron interfering with itself. Oshima et al. [2] reported evidence for the field emission of Cooper Pairs from a superconducting tip, and Josephson tunneling has been demonstrated in STM [3]. An entangled electron source generating pairs of coherent electrons with opposite spin could open the door to analogs of quantum optics experiment with entangled photons. My colleague Alexander Stibor has led an effort to reproduce these results and to directly measure electron correlations. Although correlated emission has not been confirmed, high-brightness cryogenic superconducting niobium field-emitters have been realized with potential applications in electron microscopy [4,5].

[1] D. B. Durham et al., Plasmonic Lenses for Tunable Ultrafast Electron Emitters at the Nanoscale, Phys. Rev. Appl. 12, 054057 (2019).

[2] K. Nagaoka et al., Monochromatic Electron Emission from the Macroscopic Quantum State of a Superconductor, Nature 396, 557 (1998).

[3] O. Naamanet al., Fluctuation Dominated Josephson Tunneling with a Scanning Tunneling Microscope, Phys. Rev. Lett. 87, 097004 (2001).

[4] C. W. Johnsonet al., Near-Monochromatic Tuneable Cryogenic Niobium Electron Field Emitter, Phys. Rev. Lett. 129, 244802 (2022).

[5] C. W. Johnsonet al., Superconducting Niobium Tip Electron Beam Source, http://arxiv.org/abs/2211.07734.