data and computer codes for "Hyperbolic phonon-polariton electroluminescence in 2D heterostructures"

Phonon-polaritons are electromagnetic waves resulting from the coherent coupling of photons withoptical phonons in polar dielectrics. Due to their exceptional ability to confine electric fields to deepsubwavelength scales with low loss, they are uniquely poised to enable a suite of applications beyondthe reach of conventional photonics, such as sub-diffraction imaging and near-field energy transfer.The conventional approach to exciting phonon-polaritons through optical methods, however, in-volves costly mid-infrared and terahertz coherent light sources along with near-field scanning probes,and generally leads to low excitation efficiency due to substantial momentum mismatch betweenphonon-polaritons and free-space photons. Here, we demonstrate that under proper conditions,phonon-polaritons can be excited all-electrically by velocity-saturated charge carriers. Specifically,in hexagonal boron nitride (hBN)/graphene heterostructures, by electrically driving charge carriersin ultra-high-mobility graphene out of equilibrium, we observe bright electroluminescence of hBN’shyperbolic phonon-polaritons (HPhPs) at mid-IR frequencies. The HPhP electroluminescence showsa temperature and carrier density dependence distinct from black-body or super-Planckian thermalemission. Moreover, the carrier density dependence of HPhP electroluminescence spectra revealsthat HPhP electroluminescence can arise from both inter-band transition and intra-band Cherenkovradiation of charge carriers in graphene. The HPhP electroluminescence offers fundamentally newavenues for realizing electrically-pumped, tunable mid-IR and THz phonon-polariton light sources,and efficient cooling of electronic devices.