  Detecting trace molecules remains a significant challenge. Surface-enhanced
infrared absorption (SEIRA) based on plasmonic nanostructures, particularly
graphene, has emerged as a promising approach to enhance sensing sensitivity.
While graphene-based SEIRA offers advantages such as ultrahigh sensitivity and
active tunability, intrinsic molecular damping weakens the interaction between
vibrational modes and plasmons. Here, we demonstrate ultrahigh-sensitive
molecular sensing based on synthesized complex-frequency waves (CFW). Our
experiment shows that CFW can amplify the molecular signals (~1.2-nm-thick silk
protein layer) detected by graphene-based sensor by at least an order of
magnitude and can be universally applied to molecular sensing in different
phases. Our approach is highly scalable and can facilitate the investigation of
light-matter interactions, enabling diverse potential applications in fields
such as optical spectroscopy, metasurfaces, optoelectronics, biomedicine and
pharmaceutics.
