Real-time exploration of exciton-phonon coupling to model photogeneration for photovoltaic applications

2D semiconducting materials host strongly bound excitons and play a key role in emerging applications, ranging from photovoltaics, opto-electronics and luminescence and material-based quantum information science. The TIMES Network will model the correlated exciton lattice dynamics and exciton-phonon scattering processes by treating the electron-electron and electron-nuclear interactions on the same footing. This methodology allows the prediction of exciton lifetime, transport mechanisms, and the resulting light-emission efficiency as a function of material structure and complexity. The coupling between excitons and phonons will be explored in real-time, to model coherent and non-coherent photogeneration in materials of interest for photovoltaic applications. 

Machine Learning and High-Performance Computing at the service of materials science

We further aim to construct a machine-learning based approach to relate structural complexities in 2D materials with their dielectric properties through electronic and excitonic states. Using High-Performance Computing (HPC) infrastructure, we will relate atomistic structural complexities to the parameter space determining the dielectric environment setting the electron-hole coupling. We seek to understand the change in the perturbative exciton-phonon coupling upon changes in the DFT-based electronic wavefunctions, through the construction of a learning algorithm. The aim is a feasible calculation of the exciton-phonon scattering dynamics in complex material structures as well as for a careful examination of disorder effects on the transport mechanisms.

Project: Exciton-ion dynamics in complex materials

The project will formulate the Ehrenfest dynamics to describe the exciton-ion coupling and simulate time-resolved angle-resolved photoemission spectroscopy in 2D materials.

More publications on exciton dynamics

Excitons and carriers in transient absorption and time-resolved ARPES spectroscopy: An ab initio approach
D. Sangalli
Phys. Rev. Materials 5, 083803 (2021)

First-principles ultrafast exciton dynamics and time-domain spectroscopies: Dark-exciton mediated valley depolarization in monolayer
H.-Y. Chen, D. Sangalli, M. Bernardi
Phys. Rev. Research 4, 043203 (2022)

PI: Davide Sangalli
CNR (Italy)

Project: Exciton transport in 2D materials

We aim to describe exception relaxation dynamics in 2D materials, exploring the effects of crystal packing, composition, atomic defects and spin polarisation.

More publications on exciton transport

Ultrafast exciton decomposition in transition metal dichalcogenide heterostructures
T. Amit, S. Refaely-Abramson
Phys. Rev. B 108, L220305 (2023)

Optical absorption of interlayer excitons in transition-metal dichalcogenide heterostructures
E. Barré, O. Karni, E. Liu, A. L. O’Beirne, X. Chen, H. B. Ribeiro, L. Yu, B. Kim, K. Watanabe, T. Taniguchi, K. Barmak, C. H. Lui, S. Refaely-Abramson, F. H. da Jornada, T. F. Heinz
Science 376, 406-410 (2022)

PI: Sivan Refaely-Abramson
Weizmann Institute (Israel)

Project: Ultrafast carrier and exciton dynamics in 2D materials

In this project many body techniques based on the GW+Fan-Migdal+Ehrenfest approximation will be employed to address the ultrafast dynamics of excitons, carriers and phonons in photo-excited 2D materials.

Unexplored phenomena like the elusive excitonic Mott transition and the dynamical formation of trions, biexcitons, and exciton polarons will be studied through advanced simulations of time-resolved optical and photoemission experiments.

More publications on out-of-equilibrium many body methods

Real-Time GW-Ehrenfest-Fan-Migdal Method for Nonequilibrium 2D Materials
E. Perfetto and G. Stefanucci
Nano Letters 23, 7029 (2023)

In- and out-of-equilibrium ab initio theory of electrons and phonons
G. Stefanucci, R. van Leeuwen, and E. Perfetto
Phys. Rev. X, 13, 031026 (2023)

Real-time GW : Toward an ab initio description of the ultrafast carrier and exciton dynamics in two-dimensional materials
E. Perfetto, Y. Pavlyukh, G. Stefanucci
Phys. Rev. Lett. 128, 016801 (2022)

PI: Enrico Perfetto
University Tor Vergata Roma (Italy)