Research topics - Frank Grossmann

Decoherence and Dissipation in Open Quantum Systems

What is the effect of the environment on the dynamics of a quantum system?

Since my diploma thesis on dissipative resonant tunneling in the group of Prof. Dr. U. Weiss , I have been interested in the dynamics of quantum systems coupled to their environment. Combining the Feynman-Vernon formalism with a semiclassical initial value representation (cellular dynamics) has first been done in /1/. More recently, we have used the Herman-Kluk propagator to describe non-Markovian dynamics all the way until thermalization /2/. The semiclassical hybrid dynamics has been used in /4/ to mimic the phenomena of decoherence and dissipation by using a finite bath of 20 harmonic oscillators. An implementation of the famous (Markovian) Caldeira-Leggett master equation for dissipative quantum dynamics is discussed in /3/.

How is tunneling through a barrier affected by coupling to an environment?

There has been a long debate in the literature about the effect of an environment on probabilities for tunneling in a quantum system. With the help of the BOMCA technology developped in the group of David Tannor and the stochastic Liouville-von Neumann equation we have been able to show that for energies below the barrier, tunneling is enhanced, whereas above the barrier it is suppressed /5/.

Quantum-classical transition in IR spectra

I have shown that the coupling of an anharmonic model system to a Caldeira-Leggett bath of a purely Ohmic spectral density leads to a dramatic reduction of quantum effects in the line-shape for IR absorption. Instead, if one uses an Ohmic density with Drude cutoff, quantum features do survive even for intermediate damping strength /6/.

selected publications:

  1. Frank Grossmann
    Quantum effects in intermediate-temperature dipole-dipole correlation-functions in the presence of an environment
     Journal of Chemical Physics 141, 144305 (2014)
  2. Werner Koch, Frank Grossmann, and David Tannor
    Trajectory-based non-Markovian dissipative tunneling
    Physical Review Letters 105, 230405 (2010)
  3. Christoph-Marian Goletz and Frank Grossmann
    Decoherence and dissipation in a molecular system coupled to an envorinment: An application of semiclassical hybrid dynamics
    Journal of Chemical Physics 130, 244107 (2009)
  4. Frank Grossmann and Werner Koch
    A finite-difference implementation of the Caldeira-Leggett master equation
    Journal of Chemical Physics 130, 034105 (2009)
  5. Werner Koch, Frank Grossmann, Jürgen Stockburger, and Joachim Ankerhold
    Non-Markovian Dissipative Semiclassical Dynamics
    Physical Review Letters 100, 230402 (2008)
  6. Frank Grossmann
    A semiclassical approach to dissipation in quantum mechanics,
    Journal of Chemical Physics 103, 3696 (1995)
last changes: 06/08/16