Photon Tunneling via Coupling Graphene Plasmons With Phonon Polaritons of Hexagonal Boron Nitride in Reststrahlen Bands

The photon tunneling probability is the most important thing in near-field radiative heat transfer (NFRHT). This work study the photon tunneling via coupling graphene plasmons with phonon polaritons in hexagonal boron nitride (hBN). We consider two cases of the optical axis of hBN along z-axis and x-axis, respectively. We investigate the NFRHT between graphene-covered bulk hBN, and compare it with that of bare bulk hBN. Our results show that in Reststrahlen bands, the coupling of graphene plasmons and phonon polaritons in hBN can either suppress or enhance the photon tunneling probability, depending on the chemical potential of graphene and frequency. This conclusion holds when the optiacal axis of hBN is either along z-axis or x-axis. The findings in this work not only deepen our understanding of coupling mechanism between graphene plasmons with phonon polaritons, but also provide a theoretical basis for controlling photon tunneling in graphene covered hyperbolic materials.

Whether or not the Maxwell theory works on the atomic level

In this paper, we have studied the Maxwell radiation from the electron orbiting the nucleus in an atom such as hydrogen atom. The orbiting electron is thought as two oscillating dipoles: one on [Formula: see text]-axis and the other on [Formula: see text]-axis with the same frequency. We have derived the electromagnetic wave and calculated powers of the radiation from these two oscillating dipoles, and then determined the time period it takes for the electron to change its energy levels from [Formula: see text] to [Formula: see text] due to the Maxwell radiation. Compared the time period due to the Maxwell radiation with the time period from the uncertainty principle, it is found that the two time periods are different from each other by about nine orders of magnitude. So, we are led to believe that the Maxwell theory could not be used in the quantum photo emission by the electron in an atom. Thus, we suggest that the quantum photo emission by the electron in an atom may be photon tunneling from the electron [Formula: see text] in an atom.

Enhancement of rotational vacuum friction by surface photon tunneling

When a neutral sphere is rotating near a surface in vacuum, it will experience a frictional torque due to quantum and thermal electromagnetic fluctuations. Such vacuum friction has attracted many interests but has been too weak to be observed. Here we investigate the vacuum frictional torque on a barium strontium titanate (BST) nanosphere near a BST surface. BST is a perovskite ferroelectric ceramic that can have large dielectric responses at GHz frequencies. At resonant rotating frequencies, the mechanical energy of motion can be converted to electromagnetic energy through resonant photon tunneling, leading to a large enhancement of the vacuum friction. The calculated vacuum frictional torques at resonances at sub-GHz and GHz frequencies are several orders larger than the minimum torque measured by an optically levitated nanorotor recently, and are thus promising to be observed experimentally. Moreover, we calculate the vacuum friction on a rotating sphere near a layered surface for the first time. By optimizing the thickness of the thin-film coating, the frictional torque can be further enhanced by several times.

Resonant photon emission during relative sliding of two dielectric plates

The effect of resonances in the photon emission rate in radiative heat generation and transfer, and Casimir friction at the relative sliding of two plates of polar dielectrics is studied. Resonances are of a different origin in the frequency range of the normal (NED) and anomalous (AED) Doppler effect. In the NED domain, resonances are associated with resonant photon tunneling between surface phonon/plasmon polaritons. In the AED domain resonances are associated with the instantaneous generation of excitations in both plates. While in the NED domain the resonances are finite, in the ADE domain singular resonances are possible even in the presence of dissipation in the system.