arXiv subjects

Elizabeth Gutiérrez-Meza

Publications and source records attributed to Elizabeth Gutiérrez-Meza.

4 recordsLinked to original sources

arXiv2026

Collective Excitonic Structure Governs Anomalously Weak Thermal Optical Dephasing in Conjugated Polymers

Conjugated polymer aggregates exhibit optical decoherence in the presence of strong vibronic coupling and substantial diversity in chemical structure, solid-state organization, and excitonic character. Here, we use coherence-detected and population-detected two-dimensional electronic spectroscopies to examine the temperature dependence of the homogeneous optical linewidth across a series of semiconducting polymers. Despite substantial differences in molecular architecture and solid-state organization, all polymers studied exhibit remarkably weak thermal linewidth scaling over the measured temperature range. Comparison between complementary detection modalities further shows that, while this weak temperature dependence is obust, the absolute homogeneous linewidth depends on the measured observable. This behavior reflects the different ways in which coherence- and population-detected measurements project population relaxation and pure dephasing onto the spectroscopic response. These results establish the weak thermal scaling of optical decoherence across a diverse series of conjugated polymers and show that its experimental manifestation must be interpreted in the context of the detection observable.

cond-mat.mtrl-sci↗

arXiv2024

Quantum dynamics of photophysical aggregates in conjugated polymers

Photophysical aggregates are ubiquitous in many solid-state microstructures adopted by conjugated polymers, in which $π$ electrons interact with those in other polymer chains or those in other chromophores along the chain. These interactions fundamentally define the electronic and optical properties of the polymer film. While valuable insight can be gained from linear excitation and photoluminescence spectra, nonlinear coherent excitation spectral lineshapes provide intricate understanding on the electronic couplings that define the aggregate and their fluctuations. Here, we discuss the coherent two-dimensional excitation lineshape of a model hairy-rod conjugated polymer. At zero population waiting time, we find a $π/2$ phase shift between the 0-0 and 0-1 vibronic peaks in the real and imaginary components of the complex coherent spectrum, as well as a dynamic phase rotation with population waiting time over timescales that are longer than the optical dephasing time. We conjecture that these are markers of relaxation of the photophysical aggregate down the tight manifold of the exciton band. These results highlight the potential for coherent spectroscopy via analysis of the complex spectral lineshape to become a key tool to develop structure-property relationships in complex functional materials.

cond-mat.soft↗

arXiv2022

Multidimensional coherent spectroscopy of excitons in $π$-conjugated polymers

The photophysics of $π$-conjugated polymers has been of considerable interest over the last three decades because of their organic semiconductor properties. Primary photoexcitations, Frenkel excitons, can be probed optically by means of numerous linear spectroscopies, providing a wealth of information on the the strength of excitonic coupling, the exciton coherence length, and on the nature of the disordered energy landscape. Nonetheless, there are intrinsic limitations in the information that can be obtained with linear spectroscopy compared to non-linear coherent techniques. Examples of this are the separation of homogeneous and inhomogeneous broadening contributions to the total exciton spectral lineshape, the detailed spectral structure of exciton-vibrational coupling, and correlations between optical excitations, including exciton-charge and exciton-exciton correlations. In the present work, we discuss the role of two-dimensional coherent excitation spectroscopy and review its applications towards unravelling the basic photophysics of $π$-conjugated polymers as well as polymer:fullerene blends, and we argue that these techniques are now valuable mainstream materials optical probes.

physics.chem-ph↗

arXiv2022

Identifying incoherent mixing effects in the coherent two-dimensional photocurrent excitation spectra of semiconductors

We have previously demonstrated that in the context of two-dimensional (2D) coherent electronic spectroscopy measured by phase modulation and phase-sensitive detection, an \emph{incoherent} nonlinear response, due to pairs of photoexcitations produced via linear excitation pathways, contribute to the measured signal as unexpected background [Grégoire et al., J.\ Chem.\ Phys. \textbf{147}, 114201 (2017)]. Here, we simulate the effect of such incoherent population mixing in the photocurrent signal collected from a GaAs solar cell by acting externally on the transimpedance amplifier circuit used for phase-sensitive detection, and we identify an effective strategy to recognize the presence of incoherent population mixing in 2D data. While we find that incoherent mixing is reflected by cross-talk between the linear amplitude at the two time-delay variables in the four-pulse excitation sequence, we do not observe any strict phase correlations between the coherent and incoherent contributions, as expected from modelling of a simple system.

cond-mat.mtrl-sci↗