Recent news

Oct 2019

Holstein or Peierls? Why choose? Jonathan's paper with Denis Golez from CCQ, A unification of the Holstein polaron and dynamic disorder pictures of charge transport in organic semiconductors, is posted to the arXiv.

Sep 2019

Welcome to Giulia Biffi, a visiting PhD student from Roman Krahne's group at the Italian Institute of Technology!

Sep 2019

Yeongsu's work, Optical Properties of Layered Hybrid Organic-Inorganic Halide Perovskites: A Tight-Binding GW-BSE Study, is published in J. Phys. Chem. Letters — an accurate but efficient approach for band gaps and excitons in complex, heterogeneous materials with large unit cells!

Sep 2019

Alan's paper, Ab Initio Linear and Pump-Probe Spectroscopy of Excitons in Molecular Crystals, is posted to the arXiv — the first application of atomistic periodic EE-EOM-CCSD!

Sep 2019

A great collaboration with the Weiss (Northwestern) and Darancet (ANL) groups, Large Band Edge Tunability in Colloidal Nanoplatelets, is published in Nano Letters.

Sep 2019

Welcome to our newest Columbia postdoc, Tamar Goldzak! Tami previously completed her Ph.D. with Nimrod Moiseyev at the Technion and was a postdoc with Troy Van Voorhis at MIT.

Aug 2019

A great collaboration featuring Yeongsu's theory, Dielectric disorder in two-dimensional materials is published in Nature Nanotechnology.

Aug 2019

Jul 2019

Tim receives the Presidential Early Career Award for Scientists and Engineers (PECASE). Thank you to the AFOSR for the nomination and for supporting our research! [Columbia Science News]

Jul 2019

Tim is named the winner of the 2019 Hermann Kuemmel Early Achievement Award in Many-Body Physics, "for making possible the determination of condensed phase spectra within the framework of coupled cluster theory, and for elucidating the relationship between excited-state coupled cluster theory and Green’s function diagrammatic approximations." Honored to have our work on coupled cluster recognized by an award named for one of its pioneers!

Group Members


Timothy Berkelbach

Principal Investigator

Fellow at PCTS (2014-2016)
Ph.D. Columbia University (2014)
B.A. NYU (2009)


Giulia Biffi

Visiting Graduate Student

M.S. University of Bologna (2017)
B.S. University of Bologna (2015)


James Callahan

Graduate Student

NDSEG Fellow (2019-2022)
B.A. Harvard University (2014)


Yeongsu Cho

Graduate Student

B.A. Seoul National University (2015)


Jonathan Fetherolf

Graduate Student

NSF Graduate Research Fellow (2018-2021)
B.A. Rutgers University (2016)


Tamar Goldzak

Postdoctoral Researcher

Postdoc MIT (2017-2019)
Ph.D. Technion (2017)
B.Sc. Technion (2010)


Sam Greene

Graduate Student
joint w/ J. Weare (NYU Courant)

M.S. Oxford University (2016)
Rhodes Scholar (2014-2016)
B.S. University of Chicago (2014)


Malte Lange

Graduate Student

NSF Graduate Research Fellow (2018-2021)
B.S. University of Washington (2016)


Bryan Lau

Flatiron Research Fellow

Ph.D. Northwestern University (2017)
B.S. University of Toronto (2011)


Alan Lewis

Postdoctoral Researcher

D.Phil. Oxford University (2017)
M.Chem. Oxford University (2013)


Xiao Wang

Flatiron Research Fellow

Postdoc Virginia Tech (2016-2018)
Ph.D. University of Georgia (2016)
B.S. Beihang University (2012)

Shi-Ning Sun

Undergraduate Student

Ph.D. student, Caltech

Research areas

We work on a variety of quantum-mechanical problems motivated by excited-state phenomena. This research occurs at the fascinating interface of physical chemistry, condensed-matter physics, and materials science.

Quantum dynamics and spectroscopy

Building on modern theories of quantum dynamics, we develop powerful simulation techniques for nonequilibrium and time-resolved spectroscopies. These new tools enable the accurate simulation of extremely large and complex sytems, providing new insights into excited-state structure and dynamics.

Emerging materials

We are actively exploring the excited-state behavior of fundamentally interesting and technologically promising materials, especially those that are anisotropic, layered, or low-dimensional. Particular materials of interest include conjugated polymers, organic molecular crystals, and quasi-two-dimensional inorganic semiconductors.

Condensed-phase electronic structure

Aiming towards highly accurate but insightful descriptions of electronic excitations, we formulate and apply electronic structure methods adapted for the condensed phase. Some of our favorite tools are low-energy effective theories, many-body diagrammatics, and coupled-cluster techniques.

Interested in learning more?

Check out our publications!

About Tim

Timothy Berkelbach is an Assistant Professor in the Department of Chemistry at Columbia University and a Research Scientist in the Center for Computational Quantum Physics at the Flatiron Institute. From 2016 to 2018, he was the Neubauer Family Assistant Professor in the Department of Chemistry and the James Franck Institute at the University of Chicago. He received his B.A. in physics and chemistry from NYU in 2009 and his Ph.D. in chemical physics from Columbia University in 2014, where he was a Department of Energy Office of Science Graduate Research Fellow advised by David Reichman. Tim then spent two years as a fellow of the Princeton Center for Theoretical Science, working closely with Garnet Chan. Since starting his independent career, Tim has been named as a recipient of the AFOSR Young Investigator award, the Alfred P. Sloan Research Fellowship, the NSF CAREER award, the Hermann Kuemmel Early Achievement Award in Many-Body Physics, and the Presidential Early Career Award for Scientists and Engineers (PECASE).

Columbia University

3000 Broadway, 518 Havemeyer Hall, New York NY 10027

Flatiron Institute

162 Fifth Avenue, Office 901, New York NY 10010

1 646 876 5930

Join us!

Diverse problems require diverse teams. We welcome students and postdocs of all genders, races, ages, sexual orientations, and disability statuses. If you're interested in joining us in one of the most multicultural cities in the world, contact Tim for more information on the graduate program at Columbia or postdoctoral openings at Columbia or the Flatiron Institute.