Theoretical Approach to Strongly Correlated Systems Based on the U(1) and SU(2) Symmetry Groups |
| T.K. Kopeć
Institute for Low Temperature and Structure Research, Polish Academy of Sciences, POB 1410, 50-950 Wroclaw 2, Poland |
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| The spin-rotationally invariant SU(2)×U(1) approach to the Hubbard model is extended to accommodate the charge degrees of freedom. Both U(1) and SU(2) gauge transformation are used to factorize the charge and spin contribution to the original electron operator in terms of the emergent gauge fields. By tracing out gauge bosons the form: of paired states is established and the role of antiferromagnetic correlations is explicated. We argue that in strongly correlated electron system collective instanton excitations of the phase field (dual to the charge) arise with a great degree of stability, governed by gauge flux changes by an integer multiple of 2π. Furthermore, it is shown that U(1) and SU(2) gauge fields play a similar role as phonons in the BCS theory: they act as the the "glue" for fermion pairing. |
| DOI: 10.12693/APhysPolA.121.738 PACS numbers: 74.20.-z, 74.20.Fg, 71.10.Pm |