Mode-resolved, non-local electron–phonon coupling in two-dimensional spectroscopy

Abstract

Electron-phonon coupling is fundamental to condensed-matter physics, governing various physical phenomena and properties in both conventional and quantum materials. Here we propose and demonstrate two-dimensional electron-phonon coupling spectroscopy that can directly extract the electron-phonon coupling matrix elements for specific phonon modes and different electron energies. Using this technique, we measure the electron energy dependence of the electron-phonon coupling strength for individual phonon modes. It allows us to identify distinct signatures distinguishing non-local Su-Schrieffer-Heeger-type couplings from local Holstein-type couplings. Applying this methodology to a methylammonium lead iodide perovskite, we reveal particularly different properties, for example, temperature dependence or anisotropy, of the electron-phonon couplings of two pronounced phonon modes. Our approach provides insights into the microscopic origin of the electron-phonon coupling and has potential applications in phonon-mediated ultrafast control material properties.