Hidden Dissipation in Topological Insulators: Near-field Radiation from Local Shot Noise.

Understanding dissipation in topological insulators is key to both fundamental physics and applications in spintronics, quantum computing, and low-power devices. Contrary to conventional expectations, dissipation in topological insulators need not rely on backscattering or dephasing: we show that finite-frequency local shot noise couples to the electromagnetic environment and generates near-field radiation, creating a nonlocal loss channel even at quantized conductance with vanishing global shot noise. Using a nonequilibrium Green's-function framework, we link the local noise tensor to the spectral Poynting vector and compute persistent local noise in realistic two- and three-probe quantum Hall/quantum anomalous Hall interfaces where inequivalent edge modes overlap. This produces near-field "hot spots" measurable by scanning microscopy. We also give a design criterion: enforce spin-sector orthogonality to eliminate edge-mode overlap, thereby suppressing this loss channel. Our results provide a microscopic mechanism for hidden dissipation and a practical blueprint for diagnosing and reducing energy loss in topological electronics.