##
Timothy C. Berkelbach
**Assistant Professor**

New York University, B.A. 2009

Columbia University, Ph.D. 2014

Princeton University, Postdoctoral Fellow, 2014-2016

University of Chicago, Assistant Professor, 2016-

Accolades

2016 Neubauer Family Assistant Professorship

2014 Princeton Center for Theoretical Science Postdoctoral Fellowship

2010 DOE Office of Science Graduate Research Fellowship

2008 Barry M. Goldwater Scholarship

**OFFICE:**
E133

**PHONE:**
773-834-9879

**E-MAIL: **
berkelbach@uchicago.edu

**WEB: **
http://berkelbachgroup.uchicago.edu/

**RESEARCH INTERESTS:**

**Quantum dynamics in organic molecules and crystals**

Organic molecules exhibit a rich interplay of strong electronic interactions and coupling to vibrations. These characteristics manifest in both the linear response and non-equilibrium dynamics. We develop a theoretical understanding of these materials using fully ab initio techniques as well as reduced models with first- principles parameterizations. A recent area of interest is the photophysical process of singlet exciton fission, whereby an excited singlet exciton decays into two lower- energy triplet excitons, for which we use a combination of static electronic structure and quantum relaxation techniques. More generally, we are interested exploring the theory of energy and charge transport in single molecules, where environment- induced fluctuations can have drastic implications, and we are also developing first- principles techniques for nonlinear electronic spectroscopies.

**Electronic structure of novel inorganic semiconductors**

The electronic and optical properties of inorganic semiconductors can undergo fascinating changes in situations of reduced dimensionality or hetero-structuring. Semiconductor quantum dots are a prototypical example, demonstrating a (zero- dimensional) quantum confinement effect and concomitant structure-function relationship. We are interested in understanding the dynamics of exciton and charge trapping at quantum dot surfaces, including the role played by electronically active ligands. We are also actively researching the atomic and electronic structure of quasi-two-dimensional transition metal dichalcogenides, such as MoS2, where a reduced screening strength yields inorganic excitonic complexes with unprecedented binding energies. A current area of our focus is the electronic structure of the hybrid organic-inorganic perovskites, such as methyl ammonium lead iodide.

**Methodology development for high-dimensional quantum mechanical problems**

While the theory of weakly correlated small molecules and periodic crystals is now quite mature, there is a demand for theoretical and numerical methodologies capable of treating high-dimensional problems. Examples of such problems include large interacting systems of nonitinerant spins, molecules with strong coupling between electronic and vibrational degrees of freedom, and solid-state materials with substitutional or structural disorder. We are particularly interested in quantum master-equation based techniques, which reduce complexity through an ensemble average, and the development of such frameworks beyond conventional perturbation theory. We are also currently exploring post-Hartree-Fock wavefunction-based methods, such as coupled-cluster theory, for condensed-phase materials with nontrivial electron correlation.

**References:**

J. McClain, J. Lischner, T. Watson, D. A. Matthews, E. Ronca, S. G. Louie, T. C. Berkelbach, and G. K.-L. Chan, "Spectral Functions of the Uniform Electron Gas via Coupled-Cluster Theory and Comparison to the GW and Related Approximations", arXiv:1512.04556

A. Montoya-Castillo, T. C. Berkelbach, and D. R. Reichman, "Extending the applicability of Redfield theories into highly non-Markovian regimes", J. Chem. Phys. **143**, 194108 (2015)

T. C. Berkelbach, M. S. Hybertsen, and D. R. Reichman, "Bright and dark singlet excitons via linear and two-photon spectroscopy in monolayer transition-metal dichalcogenides", Phys. Rev. B **92**, 085413 (2015)

Y. You, X.-X. Zhang, T. C. Berkelbach, M. S. Hybertsen, D. R. Reichman, and T. F. Heinz, "Observation of biexcitons in monolayer WSe2", Nature Phys. **11**, 477 (2015)

T. C. Berkelbach, M. S. Hybertsen, and D. R. Reichman, "Microscopic theory of singlet exciton fission. III. Crystalline pentacene", J. Chem. Phys. **141**, 074705 (2014)

A. Chernikov, T. C. Berkelbach, H. Hill, A. Rigosi, Y. Li, O. B. Aslan, D. R. Reichman, M. S. Hybertsen, and T. F. Heinz, "Exciton Binding Energy and Nonhydrogenic Rydberg Series in Monolayer WS2", Phys. Rev. Lett. **113**, 076802 (2014)

E. Busby, T. C. Berkelbach, B. Kumar, A. Chernikov, Y. Zhong, X.-Y. Zhu, T. F. Heinz, M. S. Hybertsen, M. Y. Sfeir, D. R. Reichman, C. Nuckolls, and O. Yaffe, "Multiphonon Relaxation Slows Singlet Fission in Crystalline Hexacene", J. Am. Chem. Soc. **136**, 10654 (2014)

S. Jang, T. C. Berkelbach, and D. R. Reichman, "Coherent quantum dynamics in donor-bridge-acceptor systems: Beyond the hopping and super-exchange mechanisms", New J. Phys. **115**, 105020 (2013)

T. C. Berkelbach, M. S. Hybertsen, and D. R. Reichman, "Theory of neutral and charged excitons in monolayer transition metal dichalcogenides", Phys. Rev. B **88**, 045318 (2013)

T. C. Berkelbach, D. R. Reichman, and T. E. Markland, "Reduced density matrix hybrid approach: An efficient and accurate method for adiabatic and non-adiabatic quantum dynamics", J. Chem. Phys. **136**, 034113 (2012)