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Wim Magnus

  • Research interest:- Statistical physics of equilibrium and non-equilibrium quantum systems, in particular the canonical and grand-canonical ensembles as well as the numerical implementation of all related quantities (free energy, chemical potential, entropy, distribution functions, correlation functions etc.).- Semiconductor physics and various theoretical investigations of quantum transport in nano-scaled devices (quantum wires, lowdimensional conductors and field-effect transistors, etc.).- Theory of quantum magnetism based on Heisenberg quantum spin systems and related models (xy-model, xxz-model, Ising model).
  • Disciplines:Electronic (transport) properties, Magnetism and superconductivity, Nanophysics and nanosystems, Semiconductors and semimetals, Quantum physics not elsewhere classified, Modelling not elsewhere classified, Nanoelectronics, Modelling and simulation, Numerical computation
  • Research techniques:- Statistical physics of non-interacting bosons and fermions in equilibrium within the canonical ensemble (CE) needs to be investigated with techniques and methodologies other than those commonly used to treat the grand-canonical ensemble (GCE). The reason is the formal constraint that fixes the number of particles N in the CE excludes the factorization of the partition function into single-particle contributions, as would be the default approach for the GCE. Instead, the CE partition function and its derived quantities can be evaluated either by numerically processing the partition function's integral representation or by elaborating on the recursive relations that are numerically stable only for sufficiently low values of N.- The examination of quantum ransport in low-dimensional systems is mainly based on the following two techniques: 1) Wigner and Wigner-Boltzmann distribution functions and 2) non-equilibrium density matrices to be determined by self-consistently solving the quantum mechanical momentum and energy balance equations, extende to higher order moments if necessary.- Quantum magnetism is being studied with thermal double-time Green functions which, by virtue of an adequate decoupling scheme, provide a unique and non-perturbative approach to compute the magnetisation of small and large systems over a wide temperature range starting from zero temperature up to the critical temperature Tc (if it exists).
  • Users of research expertise:Researchers with potential benefits:- (theoretical) physicists, chemists and researchers in biophysics and pharmaceutical sciences who need to deal with applications of statistical physics and thermodynamics;- civil engineers with a strong background in physics, who are developing new nano-scaled devices (semiconductor based or building on two-dimensional materials etc.) as well as writing the accompanying simulaton software.