Electron matter wave interferences at high vacuum pressures

The ability to trap and guide coherent electrons is gaining importance in fundamental as well as in applied physics. In this regard novel quantum devices are currently developed that may operate under low vacuum conditions. Here we study the loss of electron coherence with increasing background gas pressure. Thereby, optionally helium, hydrogen or nitrogen is introduced in a biprism interferometer where the interference contrast is a measure for the coherence of the electrons. The results indicate a constant contrast that is not decreasing in the examined pressure range between 10-9 mbar and 10-4 mbar. Therefore, no decoherence was observed even under poor vacuum conditions. Due to scattering of the electron beam with background H2-molecules a signal loss of 94% was determined. The results may lower the vacuum requirements for novel quantum devices with free coherent electrons.