https://doi.org/10.1140/epjst/e2016-60386-1
Regular Article
Non-local order parameters as a probe for phase transitions in the extended Fermi-Hubbard model
1 CNR-IOM DEMOCRITOS Simulation Center and SISSA, Via Bonomea 265, 34136 Trieste, Italy
2 Dipartimento di Fisica e Astronomia “Galileo Galilei”, Università di Padova, 35131 Padova, Italy
3 Institute for condensed matter physics and complex systems, DISAT, Politecnico di Torino, 10129 Torino, Italy
a e-mail: serena.fazzini@polito.it
Received: 7 December 2016
Revised: 18 January 2017
Published online: 26 July 2017
The Extended Fermi-Hubbard model is a rather studied Hamiltonian due to both its many applications and a rich phase diagram. Here we prove that all the phase transitions encoded in its one dimensional version are detectable via non-local operators related to charge and spin fluctuations. The main advantage in using them is that, in contrast to usual local operators, their asymptotic average value is finite only in the appropriate gapped phases. This makes them powerful and accurate probes to detect quantum phases. Our results indeed confirm that they are able to properly capture both the nature and the location of the transitions. Relevantly, this happens also for conducting phases with a spin gap, thus providing an order parameter for the identification of superconducting and paired superfluid phases.
© EDP Sciences, Springer-Verlag, 2017
