Topological thermal crystalline insulators

The disclination of a bulk crystalline lattice could host strongly localized states protected by quantized fractional charges, known as disclination states. Although disclination states of topological crystalline insulators have been extensively explored in wave systems, i.e., electromagnetic and acoustic wave systems, their experimental realizations in the diffusion process, particularly thermal diffusion, have remained underdeveloped. To bridge this gap, we theoretically model and experimentally measure topologically protected disclination states in C4, C5, and C7-symmetric thermal crystalline lattices composed of aluminum disks. The temperature evolution is tied to an effective Hamiltonian hosting topological disclination modes, which have a diffusion rate that is robust against defects. Our findings extend topological disclination phases and the physics of fractional charges from Hermitian to anti-Hermitian systems, opening new avenues for future research in thermal information processing and temperature management processes that are robust against disturbances.