A grand challenge in the chemical and physical sciences is unraveling how the properties of nanostructured materials derive from the underlying quantum mechanical fundamentals. Addressing this challenge has implications for solar energy harvesting, quantum technology, and the understanding and manipulation of biological processes. The Tempelaar Team contributes to this endeavor by the application and development of new numerical and analytical tools that allow to tractably relate microscopic principles to collective electronic and optical behavior. By targeting both specific materials and general guiding principles, we seek to advance emergent technologies as well as our fundamental understanding of the chemistry and physics found at the nano scale.
We contribute to the ever-evolving toolkit available to theoretical chemists and physicists to analytically and numerically solve quantum mechanical problems involving many interacting components such as electrons, photons, and nuclear vibrations. We are particularly interested in finding new solutions for the representation of quantum systems that are otherwise too computationally and conceptually complex. Possible solutions are by representing a subset of the constituting components classically, by treating interactions perturbatively, and by finding optimal representations based on linear algebra.
Our research is driven by a fascination for biologically relevant and emerging materials with unexpected properties. An important example can be found in photosynthesis, where solar energy is harvested and transported through disordered molecular aggregates with remarkable efficiency. Other examples are semiconducting atomic monolayers, where charges are found to exhibit exotic behaviors, and nanocavities, where photons and electronic excitations hybridize to form unique states of matter.
By positioning our theoretical research close to experimental studies we hold our models against realistic examples, but also help to optimally extract the physical information contained in measurements and to predict new experiments. This endeavor involves the simulation of experimental signals based on response functions and transition rates. We are particularly interested in multi-dimensional spectroscopic techniques that probe the nonlinear optical response of materials. However, we are always keen on broadening our horizon by learning about new experiments.
Roel (pronounced "Rule") was born in the Netherlands. He received his Ph.D. in 2015 from the University of Groningen, where he was advised by Jasper Knoester and Thomas La Cour Jansen. During his graduate years the Dutch government awarded him the Huygens Fellowship to conduct research at Temple University under guidance of Frank Spano. For his postdoctoral studies at Columbia University in the group of David Reichman he received the Rubicon Grant from the Dutch Research Council. He started as an assistant professor of Chemistry at Northwestern University in January 2020.
Anna did her B.Sc. and M.Sc. at the V.N. Karazin Kharkiv National University in Ukraine, after which the Erasmus Mundus program brought her to the University of Porto and the University of Groningen. It was in Groningen that she obtained her Ph.D. She has joined the Tempelaar Team as a postdoctoral researcher in October of this year.
Besides spending his free time building a Raman spectrometer and a receiver of satelite images based on an inexpensive radio, Alex completed a B.Sc. in chemistry at Caltech. He joined the Northwestern graduate program in chemistry in the fall of 2020.
Representative publication:Krotz, Provazza, & Tempelaar, arXiv (2021) (Link)
Justin got his B.Sc. in biotechnology at Plymouth State University. He then joined David Coker's group at Boston University, where he obtained his Ph.D in chemistry with a focus on developing methods for simulating nonadiabatic dynamical processes. Justin will be joining the Tempelaar Team as a postdoctoral researcher coming January.
At St. Olaf College, Andrew was initially torn between history and chemistry, ultimately finding his passion in the latter. After obtaining his B.A. he started as a chemistry graduate student at Northwestern in the fall of 2019.
Representative publication:Salij & Tempelaar, Phys. Rev. B (2021) (Link)
Connor Terry Weatherly
An aspiring filmmaker in high school, Connor gravitated towards chemistry in college. He obtained his B.Sc. at the University of Utah, upon which he joined Northwestern as a graduate student in chemisty in the fall of 2020.
Prior to joining Northwestern University, Roel has had the privilege of mentoring graduate students during his postdoctoral years at Columbia University.
Ian Dunn (Reichman group, Columbia University)
Ian has teamed up with Roel in unraveling the excitonic properties of molecular aggregates. He is particularly interested in how to relate the exciton band dispersion to optical properties as well as exciton-exciton annihilation.
Representative publication:Oleson, Zhu, Dunn, Bialas, Bai, Zhang, Dai, Reichman, Tempelaar, Huang, & Spano, J. Phys. Chem. C (2019) (Link)
Benedikt Kloss (Reichman group, Columbia University)
Benedikt and Roel have joined forces to develop a highly efficient representation of large electron-vibrationally coupled systems based on tensor decompositions. This has enabled them to discover anomalous mobilities of strongly-coupled excitations.
Representative publication:Kloss, Reichman, & Tempelaar, Phys. Rev. Lett. (2019) (Link)