Vibrationally Induced Molecular Magnetism

Magnetic interactions in molecular physics are typically thought of as effects of forces between magnetic dipoles caused by spins or actual angular momenta of electrically charged particles. Typical examples that already occur in the atom are the coupling of electron spin and electron angular momentum, an effect that leads to the so-called "fine structure", or the coupling of electron spin and nuclear spin, which gives rise to the "hyperfine structure" in spectroscopy. A completely different, barely explored phenomenon that is comparable to the latter effect in terms of energy splitting, but can only occur in molecules with certain symmetries, is vibrationally induced magnetic coupling. Here, an approximately circular modulation of the electron density is caused by the simultaneous excitation of two molecular vibrations, which periodically deform the molecule. In analogy to the macroscopic image of a current-carrying loop or a ring of rotating charges, this movement also generates a magnetic field that can couple again e.g. with nuclear spins. This project aims for a better understanding of this unusual type of magnetic interaction through computer simulations on selected molecules, the so-called phthalocyanines, and explores the possibility of potential applications for quantum computing. Parts of the simulations will be carried out on supercomputers, since even the correct description of the degrees of freedom of a single molecule of this size as a quantum- mechanical many-particle system still represents a computational challenge.