We are happy to announce Prof. Sibylle Gemming as an upcoming speaker in the Atomistic Modeling Seminar.

Prof. Sibylle Gemming studied chemistry at TUM, where she also completed her PhD in Theoretical Chemistry on modelling catalytic mechanisms. She subsequently moved into solid-state physics and following her habilitation in physics from Technische Universität Chemnitz, she became a research scientist and division head at Helmholtz-Zentrum Dresden- Rossendorf. Since 2020 she has held the chair for quantum mechanical processes and systems at Technische Universität Chemnitz. Research in her group focuses on modelling structure and pattern stability and formation in materials at the boundary of the quantum and classical domains.

The colloquium will focus on transport processes in single molecules and molecular layers. It will introduce a modeling framework combining density-functional theory (DFT) calculations, non-equilibrium Green’s functions, and random-walk approaches to study molecular junctions and their dynamics. The talk will further address the assembly behavior of helical oligopeptides and discuss how sterical and electronic interactions contribute to their structural organization. Finally, it will examine spin-selective transport in polypeptides and the role of geometric effects in the splitting of electron spin states.

Date: Tuesday, May 12, 2026, 10:30 am

Location: MIBE Lecture Hall

Abstract:

Reliability and resilience are key characteristics of biochemical processes that ensure the functioning of living organisms. In particular, the controlled, near-reversible low-energy transfer of charged species by suitable molecular carriers is crucial. Suitably structured organic molecules with well-defined geometric and electronic states are at the heart of such processes. The typical size range places such molecules in the transition area between classical and quantum mechanics, where sterical and electronic interactions may act cooperatively.

The colloquium focuses on transport through single molecules and molecular layers. It first introduces a modelling sequence based on first-principles density-functional calculations for the contact formation between a molecule and external contacts and non-equilibrium Green’s functions for the transport through the junction. The approach is complemented by a random-walk treatment of the molecule’s anchor group on the contact to include the junction dynamics.

Second, biomolecules often exhibit chiral centers, which enhance the sterical selectivity. At the same time, finite polypeptides can build up considerable dipole moments, which modify the assembly behaviour. DFT-based studies on the assembly of helical oligopeptides into bundles and films address the interplay of these aspects and elucidate the extent of cooperativity between sterical and electronic factors.

Third, the helicity of oligopeptides creates a geometric potential when electrons are transmitted. This potential acts like an external magnetic field, that interacts with the electron spin and is discussed as origin of spin selective transport in polypeptides. With a simplified quantum mechanical box Hamiltonian, it’s shown that this geometric potential induces the splitting of the spin states that is the prerequisite for the helicity-dependent preference of one spin direction seen in transport experiments.