Terahertz topological plasmon polaritons for robust temperature sensing

We theoretically investigate the application of topological plasmon polaritons (TPPs) to achieving robust temperature sensing. Based on an analogy of the topological edge states in the Su-Schrieffer-Heeger model, TPPs are realized in a one-dimensional intrinsic indium antimonide (InSb) microsphere chain. The existence of TPPs is demonstrated by analyzing the topology of the photonic band structures and the eigenmode distribution. Due to the temperature dependence of the permittivity of InSb in the terahertz range, the resonance frequency of TPPs can be largely tuned by the temperature. The temperature susceptibility of the TPP resonance frequency can be as high as $0.0264\phantom{\rule{0.28em}{0ex}}\mathrm{THz}$/K at room temperature, leading to a figure of merit over 150. Based on calculations on the optical local density of states (LDOS) near the chain, it is shown that the temperature susceptibility of TPPs is experimentally detectable via near-field probing techniques. Numerical results also indicate the sensing performance is immune to disorder. We further propose a robust and practical calibration method to correctly obtain the peak frequency of the LDOS spectrum due to the TPPs and then the temperature susceptibility, which is based on the ratio between the LDOS of a topological chain and that of a nontopological one. These TPPs can be potential candidates for robust temperature sensing, for which several experimental considerations are further discussed.