Temperature-dependent periodicity of the persistent current in strongly interacting systems

Abstract

The persistent current in small isolated rings enclosing magnetic flux is the current circulating in equilibrium in the absence of an external excitation. While initially studied in superconducting and normal metals, recently, atomic persistent currents have been generated in ultracold gases spurring a new wave of theoretical investigations. Nevertheless, our understanding of the persistent currents in interacting systems is far from complete, especially at finite temperatures. Here we consider the fermionic one-dimensional Hubbard model and show that in the strong-interacting limit, the current can change its flux period and sign (diamagnetic or paramagnetic) as a function of temperature, features that cannot be explained within the single-particle or Luttinger liquid techniques. Also, the magnitude of the current can counterintuitively increase with temperature, in addition to presenting different rates of decay depending on the polarization of the system. Our work highlights the properties of the strongly-interacting multi-component systems which are missed by conventional approximation techniques, but can be important for the interpretation of experiments on persistent currents in ultracold gases.