The research of our group is dedicated to solve fundamental
problems in fields of physics that are of relevance for
applications.
In this spirit we are investigating the fundamental limitations
of supercurrent flow in high-Tc superconductors, the improvement
of which is required for the fabrication of energy-efficient and
environmentally friendly superconducting cables. The use of
superconducting cables promises to cut today's immense
transmission and distribution losses of electric power in half.
Hereby it is particularly amazing that the maximum current that
can be transmitted through a high-Tc cable depends on the
symmetry of the macroscopic, quantum mechanical wave function of
the superconducting state. Likewise, we are analyzing the basic
physical phenomena that govern the behavior of strongly
correlated electron systems in oxide materials with unusual
properties. Such oxides are of interest for the use in novel
electronic devices.
To be able to match the challenges of such projects, we are
combining experimental and theoretical
methods, within the group as well as in joint projects with
academic and industrial partners in Europe, the US and Asia.
Our experimental work is based on the investigation of single
crystals, grown using an advanced zone melting process, and
of epitaxial
layers and heterostructures fabricated utilizing an optimized
epitaxial growth process based on pulsed laser deposition. With
this technique, epitaxial layers can be grown from a broad
spectrum of materials, thereby maintaining structural control
down to atomic dimensions. These samples are patterned by optical
or e-beam lithography and ion-beam etching, and are electrically
and magnetically characterized.
The improvement of the resolution of scanning probe
microscopy and the investigation of its fundamental limits is
a particularly exciting research project of our group. With these
techniques it is already in many cases possible to image the
atoms of the samples investigated. By using a novel, dynamic
atomic force microscopy technique in which extremely stiff
cantilevers, capable of oscillating with sub-nanometer
amplitudes, are used as force sensors, we succeeded imaging the
electron clouds, i.e. the orbitals, of individual atoms.
Extending this technique to measure the minute forces acting
transversally between two closely spaced bodies we have for the
first time been able to measure and analyze friction forces
between individual atoms.