Stuttgart 2012 – wissenschaftliches Programm
Q 34.46: Poster
Dienstag, 13. März 2012, 16:30–19:00, Poster.I+II
Using a single-atom tip electron source for ground state guiding of electrons — •Jakob Hammer, Johannes Hoffrogge, and Peter Hommelhoff — Max-Planck-Institut für Quantenoptik, Hans- Kopfermann-Straße 1, 85748 Garching bei München
A single-atom tip (SAT) consists of an atomically stacked pyramid on the apex of a sharp metal tip. Electron field emission from a SAT exclusively originates from the topmost atom of the pyramid. Therefore SATs are exceptionally bright and fully coherent point sources of electrons . We report on ongoing experiments to use the SAT as a source to inject electrons into a miniaturized planar ac-quadrupole guide. Here low energy electrons are confined transversally in a tight 2D harmonic microwave potential . By matching the spatial and momentum wavefunction of an incident electron with the ground state of the harmonic guiding potential, direct injection into the ground state should be feasible. Efficient ground state guiding requires a spot size of ~ 100 nm and an angular spread of ~ 1 mrad of the incoming electron wavefunction. In order to collimate the electron wavepacket transversally right after emission we are fabricating a sub-micron electrostatic lens. Miniaturization of the lens dimensions significantly reduces the lens aberrations while maintaining its focusing strength. We present the current status of the experiment as well as numerical simulations on quantum mechanical electron wavefunction propagation, revealing the efficacy of focusing close to the Heisenberg uncertainty limit.
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 J. Hoffrogge, et al., Phys. Rev. Lett. 106, 193001 (2011).