Abstract: Even though the one-dimensional (1D) Hubbard model is solvable by the Bethe ansatz, at half filling its finite-temperature T>0 transport properties remain poorly understood [1-4]. The zero-temperature finite-frequency dynamical properties of that half-filled model are also a problem of some complexity [5]. In this talk I combine that solution with symmetry to show that within that prominent 1D correlated model the charge Drude weight D (T) vanishes for T>0 and finite values of the on-site repulsion U, in the thermodynamic limit [5]. Hence there is no finite-temperature ballistic charge transport in the 1D half-filled Hubbard model. This result is exact and clarifies a long-standing open problem. It rules out that at half filling it is an ideal conductor in the thermodynamic limit. Whether at finite T and finite on-site repulsion U>0 it is an ideal insulator or a normal resistor remains though an open question. On the other hand, that at half filling the charge stiffness is finite at U=0 and vanishes for U>0 is found to result from a general transition from a conductor to an insulator or resistor occurring at U=0 for T>0. (At T=0 such a transition is the known quantum metal - Mott-Hubbard-insulator transition.) The interplay of the model eta-spin SU(2) symmetry with its hidden U(1) symmetry beyond SO(4) is found to play a central role in the unusual finite-temperature charge transport properties at half filling. The error source of the misleading predictions of Ref. [2] is shortly discussed and clarified.
[1] - X. Zotos and P. Prelovsek, Phys. Rev. B 53, 983 (1996).
[2] - Satoshi Fujimoto and Norio Kawakami, J. Phys. A 31, 465 (1998).
[3] - N. M. R. Peres, R. G. Dias, P. D. Sacramento, and J. M. P. Carmelo, Phys. Rev. B 61, 5169 (2000).
[4] - P. Prelovsek, S. El Shawish, X. Zotos, and M. Long, Phys. Rev. B 70, 205129 (2004).
[5] - R. G. Pereira, K. Penc, S. R. White, P. D. Sacramento, and J. M. P. Carmelo, Phys. Rev. B 85, 165132 (2012).
[6] - J. M. P. Carmelo, Shi-Jian Gu, and P. D. Sacramento, submitted to publication (2013).
About the Speaker: Jose Carmelo is a Professor of Physics in the University of Minho, Braga, Portugal. His research is on the interplay of correlations and low-dimensionality in condensed-matter systems and materials. He did his PhD in Physics in the University of Copenhagen in 1986 and besides his professorships in Portugal spent about twelve years in many institutions all over the world, including the Max-Planck Institute (MPI) for Condensed-Matter Research - Stuttgart, Rutgers University, University of Illinois at Urbana Champaign, CSIC - Madrid, NORDITA - Niels Bohr Institute, Los Alamos National Laboratory, MIT, University of California at Berkeley, and University of Stuttgart. He has been a Humboldt fellow (MPI) and a Senior Fulbright fellow (MIT). Since 2012 he is an associate member of CSRC in Beijing.
Date&Time: July 26, 2013 (Friday), 10:30 - 11:30 a.m.
Location: 606 Conference Room 
