Thermal diodes, which allow heat to flow in a preferential direction, are an essential component of thermal circuitry and will find applications in many fields ranging from thermal photon controls to quantum information. The quality of a thermal diode is defined by the thermal rectification ratio (TRR). Here, an ultrahigh TRR exceeding 10 5 at a small temperature difference (1–5 K) is presented based on near‐field thermal photon (NFTP) manipulation, by utilizing asymmetric gap‐variated dual terminals based on graphene/Si heterostructures and materials with contrasting thermal expansion coefficients. Analyses of the photon tunneling probability show that the colossal TRR comes from coupled and decoupled graphene surface plasmon polaritons under opposite temperature biases, remaining robust across a wide operating temperature range. Further enhancement can be achieved by tuning the Fermi level of graphene. This work demonstrates the significance of asymmetry in NFTP manipulation for thermal diode performance, achieving an ultrahigh TRR, which is at least three orders higher than the state‐of‐the‐art structures at the same small temperature difference (1–5 K), and is comparable to state‐of‐the‐art electronic diodes.

We present a theoretical study of the interaction between an atom characterized by a degenerate ground state and a reciprocal environment, such as a semiconductor nanoparticle, without the presence of external bias. Our analysis reveals that the combined influence of the electron's intrinsic spin magnetic moment on the environment and the chiral atomic dipolar transitions may lead to either the spontaneous breaking of time-reversal symmetry or the emergence of time-crystal-like states with remarkably long relaxation times. The different behavior is ruled by the handedness of the precession motion of the atom's spin vector, which is induced by virtual chiral-dipolar transitions. Specifically, when the relative orientation of the precession angular velocity and the electron spin vector is as in a spinning top, the system manifests time-crystal-like states. Conversely, with the opposite relative orientation, the system experiences spontaneous symmetry breaking of time reversal symmetry. Our findings introduce a mechanism for the spontaneous breaking of time-reversal symmetry in atomic systems, and unveil an exciting opportunity to engineer a nonreciprocal response at the nanoscale, exclusively driven by the quantum vacuum fluctuations.

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 TiSe_{2}, referred to as thermophotonic-CDW (tp-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 tp-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.

We examine the near-field radiative heat transfer between graphene-based nanostructures including parallel and laterally shifted graphene gratings and between nanoparticles and graphene gratings. We use the scattering matrix formalism together with a Local Basis Function Fourier-based method to calculate the graphene grating electromagnetic scattering. We study how the lateral shift can effectively modulate the heat transfer for different filling factor and chemical potential, and the role played by different electromagnetic modes in these structures on the radiative energy transfer. This studies has the potential to unveil new avenues for harnessing the lateral shift effect on radiative heat transfer in graphene-based nanodevices.