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

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.