Public Abstract

DE-SC0022004: Momentum-Space Imaging of Excited-State Dynamics in Molecular Materials

Award Status: Active

Institution: Research Foundation for the State University of New York d/b/a RFSUNY - Stony Brook University, Stony Brook, NY
UEI: M746VC6XMNH9
PM: El-Khoury, Patrick

Most Recent Award Date: 05/14/2026
Number of Support Periods: 5
PI: Allison, Thomas

Current Budget Period: 07/15/2026 - 07/14/2027
Current Project Period: 07/15/2025 - 07/14/2028

Public Abstract

Many current technological ambitions hinge on our ability to engineer and control the light-driven dynamics of energy, charge, and spin at the nanoscale. However, the underlying nonequilibrium dynamics initiated by the absorption of light presents major challenges to both theory and experiments. Recent breakthroughs in the field of time- and angle-resolved photoemission spectroscopy (tr-ARPES), funded by the DOE AMOS program, have now provided access to the first momentum-space images of exciton wave functions in 2D materials undergoing ultrafast dynamics. Initial studies have focused on Wannier excitons in transition metal dichalcogenides (TMDs), which are delocalized in real space over many unit cells of the crystal lattice and produce sharp features in momentum space easily discernible in ARPES measurements. In molecular systems, excitons are more localized and thus produce more diffuse momentum maps. However, these more diffuse signals still contain an enormous amount of information, and can allow one to determine the participating molecular orbitals. In this research we will apply tr-ARPES to the study of exciton dynamics in molecular materials and molecule/TMD hybrid systems. In applications, these systems have attracted substantial interest due to the large library of molecular systems one can employ in materials design and the ability to combine the strengths of inorganic 2D materials and molecular films. A series of experiments are proposed on polyacene crystals, polyacene/TMD heterostructures, and metallopthalocyanine/TMD heterostructures. Our tr-ARPES data will report on all the participating electronic states with high fidelity. The experimental data produced in this work will guide fundamental theory in the area of excited electronic states and their nonequilibrium dynamics in these complex, next generation materials, with the ultimate goal of realizing robust ab initio materials design for new energy technologies, optoelectronics, and photon-based quantum communication. Additionally, we expect the work proposed herein to continue to advance the state of the art in tr-ARPES and ultrafast spectroscopy.

Many current technological ambitions hinge on our ability to engineer and control the light-driven dynamics of energy, charge, and spin at the nanoscale. However, the underlying nonequilibrium dynamics initiated by the absorption of light presents major challenges to both theory and experiments.

Recent breakthroughs in the field of time- and angle-resolved photoemission spectroscopy (tr-ARPES), funded by the DOE AMOS program, have now provided access to the first momentum-space images of exciton wave functions in 2D materials undergoing ultrafast dynamics. Initial studies have focused on Wannier excitons in transition metal dichalcogenides (TMDs), which are delocalized in real space over many unit cells of the crystal lattice and produce sharp features in momentum space easily discernible in ARPES measurements. In molecular systems, excitons are more localized and thus produce more diffuse momentum maps. However, these more diffuse signals still contain an enormous amount of information, and can allow one to determine the participating molecular orbitals.

In this research we will apply tr-ARPES to the study of exciton dynamics in molecular materials and molecule/TMD hybrid systems. In applications, these systems have attracted substantial interest due to the large library of molecular systems one can employ in materials design and the ability to combine the strengths of inorganic 2D materials and molecular films. A series of experiments are proposed on polyacene crystals, polyacene/TMD heterostructures, and metallopthalocyanine/TMD heterostructures. Our tr-ARPES data will report on all the participating electronic states with high fidelity. The experimental data produced in this work will guide fundamental theory in the area of excited electronic states and their nonequilibrium dynamics in these complex, next generation materials, with the ultimate goal of realizing robust ab initio materials design for new energy technologies, optoelectronics, and photon-based quantum communication. Additionally, we expect the work proposed herein to continue to advance the state of the art in tr-ARPES and ultrafast spectroscopy.