Finite-Temperature Signatures of Spin Liquids in Frustrated Hubbard Model

Finite-temperature properties of the frustrated Hubbard model are theoretically examined by using the recently proposed thermal pure quantum state, which is an unbiased numerical method for finite-temperature calculations. By performing systematic calculations for the frustrated Hubbard model, we show that the geometrical frustration controls the characteristic energy scale of the metal-insulator transitions. We also find that entropy remains large even at moderately high temperature around the region where the quantum spin liquid is expected to appear at zero temperature. We propose that this is a useful criterion whether the target systems have a chance to be the quantum spin liquid or the non-magnetic insulator at zero temperature.