Title:  The Role of Coherence in Materials Photophysics

Abstract: Coherence describes collective phenomena in a wide range of classical and quantum physics, and as such it is especially important to future quantum applications that involve light-matter interactions. Because laser pulses are comprised of vast numbers of photons oscillating in unison, laser coherence can be transferred into a photoexcitation of matter. The subsequent decoherence is as a measure of the memory of that excitation and elucidates the microscopic interactions and many-body effects that lead to any observed memory. Moreover, coherent excitations can be controlled through the application of multiple laser pulses. A simple two-pulse coherent-control scheme is demonstrated to inject photocurrents in semiconductors and topological insulators [1]. Yet the complexity of coherent interactions in real devices requires better measurement in order to determine the sources of decoherence and methods to overcome them. This can be achieved with multidimensional coherent spectroscopy (MDCS), which is discussed with respect to atomic resonances and semiconductor excitons (see Fig. 1) [2]. Coherence in these model systems accesses the microscopic inner-workings of the light-matter interactions that underpin the design of photonic/optoelectronic devices, such as quantum-information processing nodes or even artificial leaves that exploit plasmon-induced energy transfer to enhance photocatalysis [3].

1. D. A. Bas, R. A. Muniz, S. Babakiray, D. Lederman, J. E. Sipe, and A. D. Bristow, “Identification of photocurrents in topological insulators,” Opt. Express 24, 23583 (2016).
2. H. Li, A. D. Bristow, M. E. Siemens, G. Moody, and S. T. Cundiff, “Unraveling quantum pathways using optical 3D Fourier-transform spectroscopy,” Nat. Commun 4, 1390 (2013).
3. J. Li, S. K. Cushing, F. Meng, T. R. Senty, A. D. Bristow, and N. Wu, “Plasmon-induced resonance energy transfer for solar energy conversion,” Nat. Photon 9, 601–607 (2015).

Host: Lex Kemper