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Research Interests
My main research interests are ground-state and spectral (dynamical)
properties of complex quantum many-particle systems - such as
solids, quantum
liquids, quantum spin chains or plasmas - with an emphasis on
- interplay of spin, charge, lattice and orbital degrees
of freedom in
materials with strong electronic correlations
(heavy fermions, high-temperature
superconducting cuprates,
colossal magnetoresistive manganites, charge-ordered
nickelates,...)
- quasi-1D electron/spin-phonon-systems
(symmetry-broken ground states, Peierls
& spin-peierls instabilties, intrinsic localized
vibrational modes, Luttinger
liquid behaviour, spin-charge-separation, metal-insulator &
insulator-insulator transitions,...)
- disorder effects (Anderson localization, percolation,
frustration, spin
glasses,...)
- magnetic short-range order in itinerant electron systems
- polaron, bipolaron &
exciton formation (self-trapping transition, optical
response, polaronic superlattices, excitonic insulators,
Bose-Einstein condensation,...)
- complex electron-hole plasmas
In all projects, we want to gain insight from a microscopic
point of view.
We employ modern analytical and numerical techniques of quantum
theory of many
partical systems. Among others, we use
- functional integral (slave-field) methods,
- Green's-function projection approaches,
- unitary transformation schemes,
- Lanczos & Jacobi-Davisdon diagonalizations,
- kernel-polynomial expansion & maximum entropy methods,
- density matrix renormalisation group.
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