0000000000349071
AUTHOR
Werner Dietsche
Mapping an electron wave function by a local electron scattering probe
A technique is developed which allows for the detailed mapping of the electronic wave function in two-dimensional electron gases with low-temperature mobilities up to $15\times {10}^{6}\;{\mathrm{cm}}^{2}\;{{\rm{V}}}^{-1}\;{{\rm{s}}}^{-1}$. Thin ('delta') layers of aluminium are placed into the regions where the electrons reside. This causes electron scattering which depends very locally on the amplitude of the electron wave function at the position of the Al δ-layer. By changing the distance of this layer from the interface we map the shape of the wave function perpendicular to the interface. Despite having a profound effect on the electron mobiliy, the δ-layers do not cause a widening of …
Spatial development of multiple-gap states in nonequilibrium superconductors
We have studied the gap instability in a superconductor under tunneling injection at high voltages by probing the spatial distribution of the phonon emission. A high sensitivity was achieved by using the fountain pressure of superfluid helium for detecting the phonons. Spatial structures were observed at gap depressions as small as 2%. From their spatial development we find that the quasiparticles diffuse into regions where their density is higher.
Kapitza resistance of laser-annealed surfaces
Our understanding of the phonon processes at the interfaces between two media is still quite rudimentary. Particularly notorious is the helium-solid interface, where the accoustic impedances differ by a large amount. It is well known that the Kapitza resistance, i.e. the thermal boundary resistance between helium and a solid, is usually up to 100 times smaller than predicted by the acoustic theory as formulated by Khalatnikov [1]. However, it was shown by J. WEBER et al. [2] that there was no discrepancy at surfaces of freshly cleaved crystals, i.e. at surfaces of exceptional good quality. Thus it is clear that surface irregularities must be responsible for the anomalous Kapitza resistance.…