Isolating Many-Particle Correlations in Time and Space

Introduction

Electronic excitations are crucial in many fields of science and engineering. Time-resolved spectroscopy is widely used to detect the dynamics of excited particles (electrons) and quasiparticles (e.g., excitons or plasmons). In the scheme of “femtochemistry” established for decades, one excitation is placed into the system by a pump pulse, and its evolution is observed by a time-delayed probe pulse. However, this does not resolve correlations between multiple excitations, making it impossible to understand important quantum phenomena.

Development of New Experimental Methods

We shall develop and apply new experimental methods to determine multi-particle correlations, based on isolating higher (than fourth) orders of perturbation theory systematically.

Separation of Contributions

• We will separate these contributions without requiring a-priori models.
• With tailored femtosecond laser pulse sequences, we circumvent the stochastic nature of light–matter interaction even though we use only classical light.
• We retrieve information from specific orders of a perturbative expansion, hitherto only accessible theoretically.

Consideration of Heterogeneous Materials

We also consider that many materials are heterogeneous. Thus, we isolate multi-particle correlations in space by combining high nonlinear orders with fluorescence microscopy and photoemission electron microscopy.

Advantages of Our Approach

• This enables us to avoid ensemble averaging.
• We obtain information for specific domains down to the single-molecule limit.

Applications of Our Methods

Our methods will be applied to determine:

1. Exciton diffusion in organic materials
2. Chiral excitonic couplings
3. Plexciton–plexciton interactions
4. Quantum coherence in multi-exciton generation
5. Phonon–phonon couplings in quantum dots
6. The role of dark states in correlated materials

Expected Impact

We expect IMPACTS to change how complex systems are studied with ultrafast spectroscopy. By overcoming the limitations of single-particle models, we seek a holistic picture of correlated dynamics, impacting our understanding and application of:

• Solar energy conversion
• Transport in functional materials
• Quantum technologies