My primary research interest lies in the fields of molecular quantum dynamics and non-linear spectroscopy. In particular, I focus on intermolecular energy, charge, and spin transfer processes, which are of central importance in various biological systems and optoelectronic devices, such as photosynthetic complexes and photovoltaic applications.
By means of first-principle quantum-chemical calculations and time-dependent quantum-mechanical simulations of such processes and their spectroscopic signatures, I aim to identify the essential molecular influence factors that either impede or enhance transfer efficiencies. A primary research objective is to provide precise guidelines for an improved rational design of functional materials. On a more fundamental level, I also investigate the potential of non-linear spectroscopic techniques to reveal sensitive dynamical information about photoactive systems and their molecular environment.
In both areas, transfer processes and spectroscopy, a rigorous treatment of quantum coherences is of paramount importance. Therefore, new simulation techniques are developed and employed, addressing quantum dynamics beyond the perturbative and secular approximation.
Huseyin Aksu, Alexander Schubert, Eitan Geva, and Barry D. Dunietz: Explaining spectral asymmetries and excitonic characters of the core pigment pairs in the bacterial reaction center using a screened range-separated hybrid functional, J. Phys. Chem B, (2019), 10.1021/acs.jpcb.9b07646
Ellen Mulvihill, Xing Gao, Yudan Liu, Alexander Schubert, Barry D. Dunietz, and Eitan Geva: Combining the mapping Hamiltonian linearized semiclassical approach withthe generalized quantum master equation to simulate electronically nonadiabatic molecular dynamics, J. Chem. Phys., 151, 074103 (2019), 10.1063/1.5110891
Yin Song, Alexander Schubert, Elizabeth Maret, Ryan K. Burdick, Barry D. Dunietz, Eitan Geva, and Jennifer P. Ogilvie: Vibronic structure of photosynthetic pigments probed by polarized two-dimensional electronic spectroscopy and ab initio calculations, Chem. Sci., 10, p.8143, (2019), https://doi.org/10.1039/C9SC02329A
Ellen Mulvihill, Alexander Schubert, Xiang Sun, Barry D. Dunietz, and Eitan Geva: A modified approach for simulating electronically nonadiabatic dynamics via the generalized quantum master equation, J. Chem. Phys., 150, p. 034101 (2019). https://doi.org/10.1063/1.5055756
Alexander Schubert, Cyril Falvo, Christoph Meier: Mixed quantum-classical simulation of the vibrational relaxation of photolyzed carbon monoxide in a hemoprotein, J. Chem. Phys., 145, p. 054108 (2016). http://dx.doi.org/10.1063/1.4959859
Alexander Schubert, Cyril Falvo, and Christoph Meier: Vibrational-coherence measurement of nonequilibrium quantum systems by four-wave mixing, Phys. Rev. A, 92, p. 053402 (2015).
Volker Settels, Alexander Schubert, Maxim Tafipolski, Wenlan Liu, Vera Stehr, Anna K. Topczak, Jens Pflaum, Carsten Deibel, Reinhold F. Fink, Volker Engel, and Bernd Engels: Identification of ultrafast relaxation processes as a major reason for inefficient diffusion in perylene-based organic semiconductors, J. Am. Chem. Soc., 136, p. 9327 (2014).http://dx.doi.org/10.1021/ja413115h
Alexander Schubert, Mirjam Falge, Martin Kess, Volker Settels, Stefan Lochbrunner, Walter T. Strunz, Frank Würthner, Bernd Engels, and Volker Engel: Theoretical analysis of the relaxation dynamics in perylene bisimide dimers excited by femtosecond laser pulses, J. Phys. Chem. A, 118, p. 1403 (2014). http://dx.doi.org/10.1021/jp412166a
Alexander Schubert, Volker Settels, Wenlan Liu, Frank Würthner, Christoph Meier, Reinhold F. Fink, Stefan Schindlbeck, Stefan Lochbrunner, Bernd Engels, and Volker Engel: Ultrafast exciton self-trapping upon geometry deformation in perylene-based molecular aggregates,J. Phys. Chem. Lett., 4 (5), p. 792 (2013). http://dx.doi.org/10.1021/jz4000752
Julian Albert, Alexander Schubert, and Volker Engel: Two-dimensional vibronic spectroscopy of molecular predissociation, New Journal of Physics, 15, p. 025008 (2013).http://dx.doi.org/10.1088/1367-2630/15/2/025008
Johannes Wehner, Alexander Schubert, and Volker Engel: Vibronic energy localization in weakly coupled small molecular aggregates, Chem. Phys. Lett., 541, p. 49 (2012).
Alexander Schubert and Volker Engel: Interference Effects in Vibronic 2D-Spectra of Diatomic Molecules, Z. Phys. Chem., 225, p. 703 (2011). https://doi.org/10.1524/zpch.2011.0087
Alexander Schubert and Volker Engel: Two-dimensional vibronic spectroscopy of coherent wave-packet motion, J. Chem. Phys., 134, p. 104304 (2011). http://dx.doi.org/10.1063/1.3560165
Alexander Schubert, Klaus Renziehausen, and Volker Engel: Mapping of quantum phases by two-dimensional vibronic spectroscopy of wave-packet revivals, Phys. Rev. A, 82, p. 013419 (2010). http://dx.doi.org/10.1103/PhysRevA.82.013419
Christof Walter, Robert Kritzer, Alexander Schubert, Christoph Meier, Otto Dopfer, and Volker Engel: Dissipative Wave Packet Dynamics of Hydrophobic→Hydrophilic Site Switching in Phenol-Ar Clusters, J. Phys. Chem. A, 114, 36, p. 9743 (2010). https://doi.org/10.1021/jp101964e