Phonon-Mediated Quasiparticle Lifetime Renormalizations in Few-Layer Hexagonal Boron Nitride

Understanding thecollective behavior of the quasiparticles insolid-state systems underpins the field of nonvolatile electronics,including the opportunity to control many-body effects for well-desiredphysical phenomena and their applications. Hexagonal boron nitride(hBN) is a wide-energy-bandgap semiconductor, showing immense potentialas a platform for low-dimensional device heterostructures. It is aninert dielectric used for gated devices, having a negligible orbitalhybridization when placed in contact with other systems. Despite itsinertness, we discover a large electron mass enhancement in few-layerhBN affecting the lifetime of the & pi;-band states. We show thatthe renormalization is phonon-mediated and consistent with both single-and multiple-phonon scattering events. Our findings thus unveil aso-far unknown many-body state in a wide-bandgap insulator, havingimportant implications for devices using hBN as one of their buildingblocks.