Non-monotonic temperature dependence of light-matter interaction in hyperbolic metamaterial due to interplay of electron-phonon scattering

Hyperbolic metamaterials (HMM) are artificially engineered materials that are congenial for light-matter interaction studies and nanophotonic applications with the hyperbolic dispersion of light propagating through them, which offers a large photonic density of states. We have explored HMM's broadband cavity-like modes and ultrasmall mode volumes, even though the system has lossy plasmonic constituents. The light-matter interaction properties of plasmonic materials strongly depend on different internal damping mechanisms. Temperature is a macroscopic parameter that controls these internal mechanisms and is reflected in their corresponding interaction behaviors. In this work, we investigated the light-matter interaction properties of the HMM system with temperature. We studied the HMM system weakly coupled to quantum emitters. This weakly coupled system shows a non-monotonicity in its broadband absorption and the emission from near-field coupling with quantum emitters. This is determined by the interplay between the electron-phonon and the phonon-phonon scatterings occurring in the metal nanowire array, effectively providing the damping with temperature. Theoretically, we confirmed the increased presence of the phonon-phonon scattering in nanowires compared to bulk metals, which plays an instrumental role in the observed light-matter interaction effects. This study could efficiently predict the use of the HMM in optics and photonics applications, with precise tuning and availability of control parameters with temperature. Also, this study could help identify the effect of increased phonon-phonon scattering in nanostructures and explore the possibility of quantifying and applying it by optical measurements.