Phonon polaritons in van der Waals polar heterostructures for broadband strong light–matter interactions

. Further, numerical calculations predict vibrational strong coupling for a few molecule monolayers with multiple molecular absorption modes and phonon polaritons in the heterostructure. Our findings suggest that broadband phonon polariton responses in van der Waals integrated heterostructures have the potential to pave the way for the development of broadband and integrated infrared devices of molecular sensing, signal processing, and energy control.