Quantum transport in 2D materials

Since the discovery of graphene, many other two-dimensional van-der-Waals materials have been isolated. We aim to unravel novel quantum phenomena in these materials via charge transport at cryogenic temperatures and variable-temperature near field microscopy in the THz and IR range. To this end we also tune the properties of our 2D systems, for example via electric fields or by interfacing them with other 2D materials.

Further reading:

A. M. Seiler, F. R. Geisenhof, F. Winterer, K. Watanabe, T. Taniguchi, T. Xu, F. Zhang and R. T. Weitz, "Quantum cascade of correlated phases in trigonally warped bilayer graphene", Nature 608, 298–302 (2022) (article online)
F. R. Geisenhof, F. Winterer, A. M. Seiler, J. Lenz, I. Martin and R. T. Weitz, "Interplay between topological valley and quantum Hall edge transport", Nat. Commun. 13, 4187 (2022) (article online)
F. Winterer, A.M. Seiler, A. Ghazaryan, F.R. Geisenhof, K. Watanabe, T. Taniguchi, M. Serbyn and R. T. Weitz, "Spontaneous Gully Polarized Quantum Hall States in ABA Trilayer Graphene", Nano Lett. 22, 8, 3317–3322, (2022) (article online)
F. R. Geisenhof, F. Winterer, A. M. Seiler, J. Lenz, T. Xu, F. Zhang and R. T. Weitz, "Quantum anomalous Hall octet driven by orbital magnetism in bilayer graphene", Nature 598, 53-58 (2021) (article online)

Project funding and collaborations

Charge transport in organic semiconductors

Organic semiconductors are of interest for use in energy harvesting, for transistor circuits in large-area electronic devices and for neuromorphic low-energy electronics. In this context, the goal of our research is to add fundamental understanding of (opto-) electronic processes in organic materials. For example, despite the long history of research in organic semiconducting materials, there is still a debate about the prevailing charge transport mechanism and dissipation mechanisms. Via precisely controlling the morphology of organic small molecules and polymers, we aim to unravel the prevailing charge transport process occurring within organic semiconductors and across semiconductor heterojunctions.

Further reading:

J. Lenz, M. Statz, K. Watanabe, T. Taniguchi, F. Ortmann and R. T. Weitz, "Charge transport in single polymer fiber transistors in the sub 100 nm regime: temperature dependence and Coulomb blockade", J. Phy. Mater. 6, 015001 (2023) (article online)
L. S. Walter, A. Axt, J. W. Borchert, T. Kammerbauer, F. Winterer, J. Lenz, S. A. L. Weber and R. T. Weitz, "Revealing and Controlling Energy Barriers and Valleys at Grain Boundaries in Ultrathin Organic Films", Small 18, 2200605 (2022) (article online)
J. Lenz, F. del Giudice, F.R. Geisenhof, F. Winterer, R.T. Weitz, "Vertical, electrolyte-gated organic transistors: continuous operation in the MA/cm2 regime and use as low-power artificial synapses", Nat. Nanotechnol. 14, 579–585 (2019) (article online)
L.S. Schaffroth, J. Lenz, V. Geigold, M. Kögl, A. Hartschuh, R.T. Weitz, "Freely suspended, van-der-Waals bound organic nm-thin functional films: mechanical and electronic characterization", Adv. Mater. 31, 1808309 (2019), (article online)