Near-Field Radiative Heat Transfer in Multilayers with Thickness-Graded Transdimensional Films

Transdimensional (TD) plasmonic materials are characterized by confinement-induced nonlocality, resulting in a thickness-dependent optical response. Multilayer structures enhance near-field radiative heat transfer through a relay mechanism, and graded structures can broaden the spectral response. We consider two multilayer structures separated by a vacuum gap, each composed of alternating TD and dielectric films, with the TD films varying in thickness along the stacking direction. The nonlocal TD response produces a redshift of approximately 13.7% and raises the peak spectral heat-transfer coefficient to 5.54 times that of the uniform Drude case. The thickness gradient broadens the high-transmission regions and raises the peak to 8.82 times that of the uniform TD case. The thickness profile controls both interfacial coupling and the optical response of individual layers. This combined control provides a potential route for enhancing and spectrally tailoring near-field radiative heat transfer.