arXiv subjects

Maksim Grechko

Publications and source records attributed to Maksim Grechko.

3 recordsLinked to original sources

arXiv2023

Signatures of Mode-Resolved, Nonlocal Electron-Phonon Coupling in Two-Dimensional Spectroscopy

Electron-phonon coupling (EPC) is foundational in condensed matter physics, determining intriguing phenomena and properties in both conventional and quantum materials. In this manuscript, we propose and demonstrate a novel two dimensional (2D) EPC spectroscopy which allows for direct extraction of EPC matrix elements for specific phonon modes and different electron energies, simultaneously. Using this technique, we are able to measure the electron-energy dependence of the EPC strength for individual phonon modes. This capability allows us to identify unique signatures distinguishing nonlocal Su-SchriefferHeeger (SSH)-type couplings from local Holstein-type couplings. In application to a methylammonium lead iodide (MAPI) perovskite, we find that two pronounced phonon modes at room temperature exhibit highly distinctive EPC behaviors, concerning strength, anisotropy, and temperature-dependence across the structural phase transition. Our approach paves the way for unraveling the microscopic origin of EPC, the change of the phonon-mode-specific EPC with external conditions, and phonon-mediated ultrafast control of condensed materials.

cond-mat.mtrl-sci↗

arXiv2023

Controlling the electro-optic response of a semiconducting perovskite coupled to a phonon-resonant cavity

Optical cavities, resonant with vibrational or electronic transitions of material within the cavity, enable control of light-matter interaction. Previous studies have reported cavity-induced modifications of chemical reactivity, fluorescence, phase behavior, and charge transport. Here, we explore the effect of resonant cavity-phonon coupling on the transient photoconductivity in a hybrid organic-inorganic perovskite. To this end, we measure the ultrafast photoconductivity response of perovskite in a tunable Fabry-Perot terahertz cavity, designed to be transparent for optical excitation. The terahertz-cavity field-phonon interaction causes apparent Rabi splitting between the perovskite phonon mode and the cavity mode. We explore whether the cavity-phonon interaction affects the material electron-phonon interaction by determining the charge carrier mobility through the photoconductivity. Despite the apparent hybridization of cavity and phonon modes, we show that the perovskite properties, in both ground (phonon response) and excited (photoconductive response) states, remain unaffected by the tunable light-matter interaction. Yet the response of the integral perovskite-terahertz optical cavity system depends critically on the interaction strength of the cavity with the phonon: the transient terahertz response to optical excitation can be increased up to 3-fold by tuning the cavity-perovskite interaction strength. These results enable tunable switches and frequency-controlled induced transparency devices.

physics.app-ph↗

arXiv2022

Extracting the sample response function from experimental two-dimensional terahertz-infrared-visible spectra

Terahertz molecular motions are often probed by high-frequency molecular oscillators in different types of non-linear vibrational spectroscopy. Recently developed two-dimensional terahertz-infrared-visible spectroscopy allows direct measuring of this coupling and, thus, obtaining site-specific terahertz vibrational spectrum. However, these data are affected by the intensity and phase of the employed laser pulses. In this work, we develop a method of extracting sample response - representing solely physical properties of a material - from experimental spectra. Using dimethyl sulfoxide (DMSO) as a model molecule to verify this method, we measure the coupling between C-H stretch vibration of its methyl groups and terahertz intramolecular twist and wagging modes.

physics.chem-ph↗