Charge-order states of broken symmetry, such as charge density wave (CDW), are able to induce exceptional physical properties, however, the precise understanding of the underlying physics is still elusive. Here, we combine fluctuational electrodynamics and density functional theory to reveal an unconventional thermophotonic effect in CDW-bearing TiSe2, referred to as thermophotonic-CDW (????⁢????-CDW). The interplay of plasmon polariton and CDW electron excitations give rise to an anomalous negative temperature dependency in thermal photons transport, offering an intuitive fingerprint for a transformation of the electron order. Additionally, the demonstrated nontrivial features of ????⁢????-CDW transition hold promise for a controllable manipulation of heat flow, which could be extensively utilized in various fields such as thermal science and electron dynamics, as well as in next-generation energy devices.

We investigate the near-field radiative heat transfer between a normally and/or laterally shifted nanoparticle and a planar fused silica slab coated with a strip graphene grating. For this study, we develop and use a scattering matrix approach derived from Fourier modal method augmented with local basis functions. We find that adding a graphene sheet coating on the slab can already enhance the heat flux by about 85%. We show that by patterning the graphene sheet coating into a grating, the heat flux is further increased, and this happens thanks to the a topological transition of the plasmonic modes from circular to hyperbolic one, which allows for more energy transfer. The lateral shift affects the accessible range of high-???? modes and thus affects the heat flux, too. By moving the nanoparticle laterally above the graphene grating, we can obtain an optimal heat flux with strong chemical potential dependence above the strips. For a fixed graphene grating period (????=1µ⁢m) and not too large normal shift (separation ????<800nm), two different types of lateral shift effects (e.g., enhancement and inhibition) on heat transfer have been observed. As the separation ???? is further increased, the lateral shift effect becomes less important. We show that the lateral shift effect is sensitive to the geometric factor ????/????. Two distinct asymptotic regimes are proposed: (1) the inhibition regime (????/????<0.85), where the lateral shift reduces the heat transfer and (2) the neutral regime (????/????≥0.85) where the effect of the lateral shift is negligible. In general, we can say that the geometric factor ????/????≈0.85 is a critical point for the lateral shift effect. Our predictions can have relevant implications to the radiative heat transfer and energy management at the nano/microscale.

Polariton manipulations introduce novel approaches to modulate the near-field radiative heat transfer (NFRHT). Our theoretical investigation in this study centers on NFRHT in graphene-covered Weyl semimetals (WSMs). Our findings indicate variable heat flux enhancement or attenuation, contingent on chemical potential of graphene. Enhancement or attenuation mechanisms stem from the coupling or decoupling of surface plasmon polaritons (SPPs) in the graphene/WSM heterostructure. The graphene-covered WSM photon tunneling probabilities variation is demonstrated in detail. This research enhances our comprehension of SPPs within the graphene/ WSM heterostructure and suggests methods for actively controlling NFRHT.