Speaker
Daniela Pfannkuche
Description
Dynamical processes set yet another degree of complexity to
the many-body problem. With the advent of ultrafast
measuring techniques modern experiments often leave the
regime of adiabaticity or linear response. The evolution of
quantum systems on short time scales subject to strong
disturbances then becomes relevant. In this contribution, I
will present two different examples that demonstrate aspects
of non-equilibrium dynamics in many-body quantum systems.
The first example considers the temporal evolution of a closed
many-body-system represented by a simple molecule being
exposed to a strong ionizing light pulse. Solving the
time-dependent Schrödinger equation reveals different
processes in the charge dynamics following ionization. It
will be demonstrated that a proper choice of electron-hole
excitations is crucial for capturing the essential physics.
The second example features the non-equilibrium dynamics of
an open quantum system. The spin of a magnetic ad-atom
residing on the surface of a non-magnetic substrate is
exposed to the tunneling current of a scanning tunneling
microscope. Spin torque of the tunneling electrons induces
spin-dynamics of the surface spin. A master-equation
approach is used to solve von-Neumann's equation of motion
for the reduced density matrix of the surface spin. Challenges
in computing the short time dynamics of the system by
different methods are being exhibited.
