  We explore a novel approach to achieving anisotropic thermal photon
tunneling, inspired by the concept of parity-time symmetry in quantum physics.
Our method leverages the modulation of constitutive optical parameters,
oscillating between loss and gain regimes. This modulation reveals a variety of
distinct effects in thermal photon behavior and dispersion. Specifically, we
identify complex tunneling modes through gain-loss engineering, which include
thermal photonic defect states and Fermi-arc-like phenomena, which surpass
those achievable through traditional polariton engineering. Our research also
elucidates the laws governing the evolution of radiative energy in the presence
of gain and loss interactions, and highlights the unexpected inefficacy of gain
in enhancing thermal photon energy transport compared to systems characterized
solely by loss. This study not only broadens our understanding of thermal
photon tunneling but also establishes a versatile platform for manipulating
photon energy transport, with potential applications in thermal management,
heat science, and the development of advanced energy devices.
