Condensed Matter Physics Seminar

Prof Klaus Müller-Dethlefs, The Photon Science Institute, University of Manchester

Friday 15 May 2015, 1500-1600
C1 Physics Building

Observation of solitons in a quantum degenerate plasma

We are reporting a surprising result: the observation of self-sustained solitons in a quantum degenerate plasma by time-of-flight measurement without the presence of a significant magnetic field.

We are producing an ultra-cold Rydberg plasma by laser threshold ionization of NO molecules in the high-density, high-collision rate expansion region of a pulsed supersonic free jet expansion (10% NO in Ne) close to the nozzle. The plasma produced shows little expansion and has an extremely long lifetime.

For the plasma densities of < 10^16 cm–3 reached in our experiments the electrons should become quantum degenerate, i.e. the electron de Broglie wavelength becomes larger than the mean distance between particles, or the Wigner-Seitz radius. According to textbook plasma physics the degeneracy condition for the electrons in an ultra-cold ion-electron plasma is fulfilled for an initial electron temperature of 0.1 K and a density above 10^13 cm–3. When the plasma cloud approaches the metal plate (1), which has an aperture, a high-voltage pulse is applied and the plasma is separated into a negatively and positively charged cloud. After passing through aperture (1) a second high voltage pulse then generates, for a specific voltage, very narrow (2ns) peaks in the time-of-flight (tof) spectrum (red). Detuning the voltage of the second pulse (green, blue) broadens the TOF peaks significantly.