T > 0 transport properties in integrable quantum lattice systems

We show that a generalized charge SU(2) symmetry of the one-dimensional (1D) Hubbard model in an infinitesimal flux φ generates half-filling states from metallic states which lead to a finite charge stiffness D(T ) at finite temperature T , whose T dependence we study. Our results are of general nature for many integrable quantum lattice systems, reveal the microscopic mechanisms behind their exotic T > 0 transport properties and the interplay with T = 0 quantumphase transitions, and contribute to the further understanding of the transport of charge in systems of interacting ultracold fermionic atoms in 1D optical lattices, quasi-1D compounds, and 1D nanostructures. There has been a recent increasing interest in the unusual transport and spectral properties of systems of interacting ultracold fermionic atoms in one-dimensional (1D) optical lattices [1] and a renewed interest in those of quasi-1D carbon nanotubes, ballistic wires, and quasi-1D compounds [2, 3]. Quantum effects are strongest at low dimensionality leading to unusual phenomena such as charge-spin separation at all energies [3] and persistent currents in mesoscopic rings [4]. The ultracold atom technology can realize a 1D closed optical lattice experimentally with a tunable boundary phase twist capable of inducing atomic ”persistent currents” [1]. Thus, the further understanding of the microscopic mechanisms behind the transport of charge in low-dimensional correlated systems and materials is a topic of high scientific and technological interest. Recently there has been an enormous grow in the literature on the quantum phase transitions in such systems [5]. For instance, the relation of the unusual T > 0 charge-transport properties observed in low-dimensional correlated systems to their T = 0 quantum phase transitions is also a problem which is far of being fully understood. For the 1D Hubbard model [6] or any other interacting electronic quantum system defined in a 1D lattice of Na sites of length L = aNa = Na (kB = ~ = a = −e = 1) the T > 0 (a)E-mail: [email protected]