Temperature-dependent band structure of the Kondo insulator

We present a quantum Monte Carlo (QMC) study of the temperature dependent dynamics of the Kondo insulator. Working at the so-called symmetrical point allows us to perform minus-sign free QMC simulations and thus leach temperatures of less than 1% of the conduction-electron bandwidth. Study of the temperature dependence of the single-particle Green's function and dynamical spin-correlation function shows a surprisingly intricate low-temperature band structure and gives evidence for two characteristic temperatures, which we identify with the Kondo and coherence temperatures, respectively. In particular, the data show a temperature-induced metal-insulator transition at the coherence temperature.