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Biexciton formation and exciton coherent coupling in layered GaSe



Prasenjit Dey, Jagannath Paul, Galan Moody, Christopher Stevens, Neil Glikin, Zakhar Kovalyuk, Zakhar Kudrynskyi, Aldo Romero, Andres Cantarero, David Hilton


Nonlinear two-dimensional Fourier transform (2DFT) and linear absorption spectra of layered GaSe exhibit two peaks at the direct 1s exciton energy. The doublet is assigned to a splitting of the excitonic ground state into the singlet and triplet. The 2DFT measurements reveal coherent energy transfer between the triplet and the singlet. Polarization dependent 2DFT spectra expose an additional peak likely originating from bound biexcitons. The polarization dependent 2DFT spectra are well reproduced by simulations using the optical Bloch equations for a four level system, where many-body eff ects are included phenomenologically. Although biexciton e ffects are thought to be strong in this material, only moderate contributions from bound biexciton formation can be observed in the 2DFT spectra. The biexciton binding energy of 2 meV was estimated from the separation of the peaks in the 2DFT spectra. Temperature dependent absorption and 2DFT measurements, combined with 'ab initio' theoretical calculations of the phonon spectra, indicate strong interaction with the A1' phonon mode. Excitation density dependent 2DFT measurements reveal excitation induced dephasing and provide a lower limit for the homogeneous linewidth of the excitons in the present GaSe crystal.
Journal of Chemical Physics


exciton, many-body interactions, nonlinear spectroscopy, two-dimensional materials, GaSe


Dey, P. , Paul, J. , Moody, G. , Stevens, C. , Glikin, N. , Kovalyuk, Z. , Kudrynskyi, Z. , Romero, A. , Cantarero, A. and Hilton, D. (2015), Biexciton formation and exciton coherent coupling in layered GaSe, Journal of Chemical Physics, [online], (Accessed May 26, 2024)


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Created April 13, 2015, Updated October 12, 2021