Research projects

1: Semiclassical theories

Collaborators: Profs. R.K. Bhaduri (McMaster Univ., Canada), M.V.N. Murthy (IMSC, Madras, India), J. Law (Univ. of Guelph, Canada); Dr. A. Sugita (Kyoto University, Japan); Drs. A. Magner, D. Fedotkin and F. Ivanyuk (INR, Kiev); Dr. S. Frauendorf (FZ Rossendorf), M. Sieber (Univ. Bristol); Dr. O. Zaitsev, Dr. K. Tanaka, Dipl.-Phys. Ch. Amann, J. Kaidel, M. Pletyukhov, Regensburg
Support: DFG, EU (TMR, INTAS), NSERC (Canada).

We develop semiclassical methods for describing finite bound fermion systems. A: Extended Thomas-Fermi (ETF) model for average properties (binding energies, densities). The ETF model is extended to two-dimensional systems including magnetic fields and spin degrees of freedom. B: Periodic orbit theory (POT) for quantum shell effects. We study extensions of Gutzwiller's POT to include continuous symmetries, symmetry breaking, bifurcations of classical orbits; inclusion of external magnetic fields; grazing, diffraction and scattering effects (e.g. from boundaries or from a magnetic flux tube); inclusion of spin degrees of freedom (e.g. spin-orbit interactions). We develop extensions to transport properties and collective vibrations (linear response). Gross-shell properties described by the shortest periodic orbits; coexistence of chaos and order in non-integrable systems. In this context: study of non-linear dynamics (in particular: bifurcations on the road to chaos).

For a textbook on "Semiclassical Physics", look here .

2: Physics of finite fermion systems

Collaborators: Profs. J. Meyer (Univ. Lyon-I), P.G. Reinhard (Univ. Erlangen), M.V.N. Murthy (IMSC, Madras, India); Drs. S. M. Reimann (Lund Inst. Technology, Sweden), M. Sieber (Univ. of Bristol, UK); Drs. M. Seidl, A. Sugita, K. Tanaka, O. Zaitsev, Dipl.-Phys. M. Pletyukhov, Ch. Amann, J. Blaschke, P. Meier and S. Kümmel, Regensburg

We investigate properties of finite fermion systems (nuclei, metal clusters and semiconductor quantum dots): masses, densities, deformations, collective excitations; in particular shell effects. Fully microscopic selfconsistent calculations are done in the Hartree-Fock (HF) approach with effective Skyrme interactions for nuclei, and in the density functional (DFT) approach in local density approximation (LDA) by solving the Kohn-Sham equations in one, two and three dimensions. Accurate exchange-correlation functionals in terms of Kohn-Sham orbitals are developed in particular for strongly correlated electronic systems. Selfconsistent calculations for average properties are done in the ETF model (see 1. above). Shell effects are obtained quantum-mechanically with the Strutinsky shell-correction method and semiclassically with the POT (see 1. above). Special topics in nuclei: shapes of ground-states, isomers and during fission ; giant resonances. In metal clusters: mass distributions and magic numbers ; ionization potentials and electron affinities; supershell structure; Mie plasmon (resonance in photoabsorption cross section); deformations through plasmon splitting; static polarizability; jellium model and beyond; ionic structure through Monte-Carlo molecular dynamics with phenomenological local pseudopotentials that are used consistently in bulk, atoms and clusters. In quantum dots and other mesoscopic systems: conductance oscillations in magnetic fields. See here for an overview.

For an introduction "Semiclassical approaches to mesoscopic systems", look here .