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Dr. Jan Wilhelm


Research

Ultrafast electron dynamics in topological insulators


Absorption and emission of light from Dirac fermions.

Recent progress in laser technology made it possible to generate high-intensity ultra-short laser pulses. When irradiating materials with such a laser pulse, the electric field of the pulse accelerates electrons in the material. Fingerprints of the ultrafast electron dynamics are encoded in the emission spectrum which is, however, often hard to interpret without a corresponding simulation. We simulate ultrafast electron dynamics to better understand the underlying mechanisms, for example of high harmonic emission or direct-current generation. For simulations, we employ our open-source package CUED [18, 20, 23].

GW method development

GW is a state-of-the-art method to compute band structures of solids and electronic levels in molecules. GW calculations are often used to study the electronic structure of these systems, to screen promising materials candidates, or to calculate parameters for the use in models. Today's largest supercomputers are required when applying GW to systems with more than hundred atoms in the simulation. Such large-scale calculations are used to model nanoscale molecules and materials with interfaces and defects, for example tailor-made graphene structures used for all-carbon electronics [11, 14, 15, 21] or defected two-dimensional materials that are promising candidates for single-photon quantum emitters.

'GW meter': Computational cost
of GW can be reduced to O(N²).

We work on a low-scaling GW algorithm to enable GW calculations on molecules and unit cells with thousands of atoms. Our goal is to provide a GW algorithm that is capable of treating realistic models of interfaces, defects and nanoscale molecules. The GW developments are implemented in the widely used open-source package CP2K [10, 17, 19].

Short CV

since 2019: Scientific Staff (Akademischer Rat), University of Regensburg
2017 - 2019: Research Scientist, BASF, Ludwigshafen
2014 - 2017: PhD in Theoretical Chemistry (with Prof. J. Hutter), University of Zurich
2009 - 2016: Studies of Physics and Mathematics, Karlsruhe Institute of Technology


Publications

The publication list is also available on Google Scholar.

[23] M. Graml, M. Nitsch, A. Seith, F. Evers, J. Wilhelm, Theory of non-integer high-harmonic generation in a topological surface state, arXiv:2205.02631 (2022).

[22] L. Li, J. Low, J. Wilhelm, G. Liao, S. Gunasekaran, C. Prindle, R. Starr, D. Golze, C. Nuckolls, M. Steigerwald, F. Evers, L. Campos, X. Yin, L. Venkataraman, Highly Conducting Single-Molecule Topological Insulators Based on Mono-and Di-Radical Cations, ChemRxiv qz9xr (2022).

[21]  G. Borin Barin, Q. Sun, M. Di Giovannantonio, C. Du, X. Wang, J. P. Llinas, Z. Mutlu, Y. Lin, J. Wilhelm, J. Overbeck, C. Daniels, M. Lamparski, H. Sahabudeen, M. L. Perrin, J. I. Urgel, S. Mishra, A. Kinikar, R. Widmer, S. Stolz, M. Bommert, C. Pignedoli, X. Feng, M. Calame, K. Müllen, A. Narita, V. Meunier, J. Bokor, R. Fasel, P. Ruffieux: Growth optimization and device integration of narrow-bandgap graphene nanoribbons, arXiv:2202.01101 (2022).

[20]  C. P. Schmid, L. Weigl, P. Grössing, V. Junk, C. Gorini, S. Schlauderer, S. Ito, N. Hofmann, D. Afanasiev, J. Crewse, K. A. Kokh, O. E. Tereshchenko, J. Güdde, F. Evers, J. Wilhelm, K. Richter, U. Höfer, and R. Huber: Tunable non-integer high-harmonic generation in a topological insulator, Nature 593, 385-390 (2021).

[19]  J. Wilhelm, P. Seewald, D. Golze: Low-scaling GW with benchmark accuracy and application to phosphorene nanosheets, J. Chem. Theory Comput. 17, 1662 (2021).

[18]  J. Wilhelm, P. Grössing, A. Seith, J. Crewse, M. Nitsch, L. Weigl, C. Schmid, F. Evers: Semiconductor Bloch-equations formalism: Derivation and application to high-harmonic generation from Dirac fermions, Phys. Rev. B 103, 125419 (2021).

[17]  T. D. Kühne, M. Iannuzzi, M. Del Ben, V. V. Rybkin, P. Seewald, F. Stein, T. Laino, R. Z. Khaliullin, O. Schütt, F. Schiffmann, D. Golze, J. Wilhelm, S. Chulkov, M. H. Bani-Hashemian, V. Weber, U. Borstnik, M. Taillefumier, A. S. Jakobovits, A. Lazzaro, H. Pabst, T. Müller, R. Schade, M. Guidon, S. Andermatt, N. Holmberg, G. K. Schenter, A. Hehn, A. Bussy, F. Belleflamme, G. Tabacchi, A. Glöß, M. Lass, I. Bethune, C. J. Mundy, C. Plessl, M. Watkins, J. VandeVondele, M. Krack, J. Hutter: CP2K: An electronic structure and molecular dynamics software package - Quickstep: Efficient and accurate electronic structure calculations, J. Chem. Phys. 152, 194103 (2020).

[16]  T. T. Duignan, G. K. Schenter, J. L. Fulton, T. Huthwelker, M. Balasubramanian, M. Galib, M. D. Baer, J. Wilhelm, J. Hutter, M. Del Ben, X. S. Zhao, C. J. Mundy: Quantifying the hydration structure of sodium and potassium ions: taking additional steps on Jacob’s Ladder, Phys. Chem. Chem. Phys. 22, 10641-10652 (2020).

[15]  J. I. Urgel, S. Mishra, H. Hayashi, J. Wilhelm, C. A. Pignedoli, M. Di Giovannantonio, R. Widmer, M. Yamashita, N. Hieda, P. Ruffieux, H. Yamada, R. Fasel: On-surface light-induced generation of higher acenes and elucidation of their open-shell character, Nat. Commun. 10, 861 (2019).

[14]  D. Beyer, S. Wang, C. A. Pignedoli, J. Melidonie, B. Yuan, C. Li, J. Wilhelm, P. Ruffieux, R. Berger, K. Müllen, R. Fasel, X. Feng: Graphene Nanoribbons Derived From Zigzag Edge-Encased Poly (para-2, 9-dibenzo [bc, kl] coronenylene) Polymer Chains, J. Am. Chem. Soc. 141, 2843-2846 (2019).

[13]  J. Wilhelm, J. VandeVondele, V. V. Rybkin: Dynamics of the Bulk Hydrated Electron from Many‐Body Wave‐Function Theory, Angew. Chem. Int. Ed. 58, 3890-3893 (2019).

[12]  D. Golze, J. Wilhelm, M. J. van Setten, P. Rinke: Core-level binding energies from GW: An efficient full-frequency approach within a localized basis, J. Chem. Theory Comput. 14, 4856-4869 (2018).

[11]  M. Di Giovannantonio, J. I. Urgel, U. Beser, A. V. Yakutovich, J. Wilhelm, C. A. Pignedoli, P. Ruffieux, A. Narita, K. Müllen, R. Fasel: On-Surface Synthesis of Indenofluorene Polymers by Oxidative Five-Membered Ring Formation, J. Am. Chem. Soc. 140, 3532-3536 (2018).

[10]  J. Wilhelm, D. Golze, L. Talirz, J. Hutter, C. A. Pignedoli: Toward GW calculations on thousands of atoms, J. Phys. Chem. Lett. 9, 306-312 (2018).

[9]  J. Wilhelm, J. Hutter: Periodic GW calculations in the Gaussian and plane-waves scheme, Phys. Rev. B 95, 235123 (2017).

[8]  D. Golze, N. Benedikter, M. Iannuzzi, J. Wilhelm, J. Hutter: Fast evaluation of solid harmonic Gaussian integrals for local resolution-of-the-identity methods and range-separated hybrid functionals, J. Chem. Phys. 146, 034105 (2017).

[7]  J. Wilhelm, P. Seewald, M. Del Ben, J. Hutter: Large-scale cubic-scaling random phase approximation correlation energy calculations using a Gaussian basis, J.Chem. Theory Comput. 12, 5851-5859 (2016).

[6]  J. Wilhelm, M. Del Ben, J. Hutter: GW in the Gaussian and plane waves scheme with application to linear acenes, J. Chem. Theory Comput. 12, 3623-3635 (2016).

[5]  J. Wilhelm, M. Walz, F. Evers: Ab initio spin-flip conductance of hydrogenated graphene nanoribbons: Spin-orbit interaction and scattering with local impurity spins, Phys. Rev. B 92, 014405 (2015).

[4]  M. Walz, J. Wilhelm, F. Evers: Current patterns and orbital magnetism in mesoscopic dc transport, Phys. Rev. Lett. 113, 136602 (2014).

[3]  J. Wilhelm, M. Walz, F. Evers: Ab initio quantum transport through armchair graphene nanoribbons: Streamlines in the current density, Phys. Rev. B 89, 195406 (2014).

[2]  N. Bajales, S. Schmaus, T. Miyamashi, W. Wulfhekel, J. Wilhelm, M. Walz, M. Stendel, A. Bagrets, F. Evers, S. Ulas, B. Kern, A. Böttcher, M. M. Kappes: C58 on Au (111): A scanning tunneling microscopy study, J. Chem. Phys. 138, 104703 (2013).

[1]  J. Wilhelm, M. Walz, M. Stendel, A. Bagrets, F. Evers: Ab initio simulations of scanning-tunneling-microscope images with embedding techniques and application to C58-dimers on Au(111), Phys. Chem. Chem. Phys. 15, 6684-6690 (2013).


Book

Stoffumwandlungen und Bilanzen: Ein Lehrbuch für Wirtschaftsingenieure, two editions published in 2012 and 2013 (in German; book for Industrial Engineering students at Karlsruhe Institute of Technology to prepare for Chemical Engineering exam; passing the exam was mandatory until 2015 to obtain B.Sc. degree in Industrial Engineering; ISBN: 978-3000431555)


Dr. Jan Wilhelm

Computational Condensed Matter Theory Group

Institute of Theoretical Physics
Universitätsstraße 31
D-93053 Regensburg


Contact
Email: jan.wilhelm@ur.de
Phone: +49 (0) 941 943 2040
Office: PHY 3.1.24