arXiv subjects

Luisa Brenneis

Publications and source records attributed to Luisa Brenneis.

4 recordsLinked to original sources

arXiv2026

Nonlinear order separation in two-dimensional electronic spectroscopy quantifies properties of higher-excited states

Two-dimensional (2D) spectroscopy combines high temporal and spectral resolution, allowing the observation of ultrafast energy transfer and the separation of homogeneous and inhomogeneous broadening. Typically, 2D spectroscopy is dominated by the lowest-order nonlinear signal for a given phase-matching configuration while signals of higher order are present but difficult to access separately. Recently, we introduced a technique to separate nonlinear orders in 2D spectroscopy by systematically varying the intensity of the pump pulses and appropriate post-processing. Here, we unravel the full potential of higher-order 2D spectroscopy by separating multiple nonlinear orders at different multi-quantum positions. As an example, we investigate a squaraine dimer. Using a theoretical model, we find excellent qualitative and quantitative agreement throughout all nonlinear orders and multi-quantum positions. Our simulations demonstrate the sensitivity and information content hidden in the higher-order spectra such as transition dipole moments and energy levels even of highly excited states. Our results pave the way for establishing higher-order spectroscopy as a unique extension of multidimensional spectroscopy, providing access to highly excited states and their properties encoded in successive orders of nonlinearity.

physics.chem-ph↗

arXiv2026

Disentangling Single- and Biexciton Dynamics with Photoelectron-Detected Two-Dimensional Electronic Spectroscopy

Action-detected two-dimensional (2D) spectroscopy resolves the time-dependent nonlinear optical response of a quantum system by recording incoherently detected observables such as fluorescence, photoelectrons, or photocurrents which reflect the system's excited-state population. Processes such as exciton-exciton annihilation alter this population and obscure, for instance, energy transfer processes. This limits the information available from action-detected 2D spectra compared to their coherently detected counterparts. Here we investigate time gating and kinetic-energy filtering in photoelectron-detected 2D spectroscopy to disentangle various processes. We implement a numerical simulation protocol that allows us to calculate photoelectron-detected 2D spectra for various systems, demonstrating that time gating can extract the same information as coherently detected 2D spectroscopy, even when annihilation is present. Furthermore, we can directly infer annihilation dynamics. Kinetic-energy filtering additionally enables the isolation of specific excited-state dynamics. Our simulations demonstrate that time gating and kinetic-energy filtering are promising extensions for photoelectron-detected 2D spectroscopy.

physics.chem-ph↗

arXiv2025

Separating orders of response in transient absorption and coherent multi-dimensional spectroscopy by intensity variation

Interpretation of time-resolved spectroscopies such as transient absorption (TA) or two-dimensional (2D) spectroscopy often relies on the perturbative description of light-matter interaction. In many cases the third order of nonlinear response is the leading and desired term. When pulse amplitudes are high, higher orders of light-matter interaction can both distort lineshapes and dynamics and provide valuable information. Here, we present a general procedure to separately measure the nonlinear response orders in both TA and 2D spectroscopies, using linear combinations of intensity-dependent spectra. We analyze the residual contamination and random errors and show how to choose optimal intensities to minimize the total error in the extracted orders. For an experimental demonstration, we separate the nonlinear orders in the 2D electronic spectroscopy of squaraine polymers up to 11$^{th}$ order.

physics.chem-ph↗

arXiv2025

Plasmonic Su-Schrieffer-Heeger chains with strong coupling amplitudes

Plasmonic many-particle systems with precisely tuned resonances and coupling strengths can exhibit emergent collective properties governed by universal principles. In one-dimensional chains with alternating couplings, known as Su-Schrieffer-Heeger (SSH) systems, this includes the formation of topologically protected mid-gap modes whose intensities localize at the chain's ends. This subwavelength localization at optical frequencies is crucial for achieving strong coupling of mid-gap modes to two-level systems under ambient conditions, extending topological protection to hybrid light-matter states. Here, we have fabricated SSH chains from plasmonic nanoslit resonators with strong inter-resonator coupling. The alternating distance between the nanoslit resonators is controlled with sub-nanometer precision, enabling accurate prediction and experimental observation of topologically protected mid-gap modes via photoemission electron microscopy (PEEM). Our results open the path towards experimental realizations of two-dimensional photonic metasurfaces exhibiting higher-order topological modes that can be strongly coupled to single emitters and quantum materials at ambient conditions.

physics.optics↗