Direct detection of axion-like particles in Bismuth-based topological insulators

In recent years, a new field emerged in dark matter community and immediately attracted a multitude of theorists and experimentalists, that of light dark matter direct detection in electronic systems. The phenomenon is similar to nuclear recoil in elastic scattering between dark matter and nucleus but with different kinematics. Due to the small energy gap, the electronic system can probe sub-GeV dark matter rather than nucleus target. In particular, the absorption into materials can even detect ultralight dark matter within mass around meV. In terms of the equivalence between optical conductivity and absorption cross-section, axion detection can be computed in Bismuth-based topological insulators. It is found that topological insulator has strong sensitivity on axion and provides a complementary direct detection to superconductor and semiconductors. The novelty of topological insulator is that the thin film could even obtain the same sensitivity as a superconductor.