Abstract
We propose an eigenoperator scheme to study the lattice model of interacting spinless fermions at half filling and show that this model possesses a hidden form of reflection positivity in its Majorana fermion representation. Based on this observation, we prove rigourously that the ground state of this model is either unique or doubly degenerate if the lattice size is even, and is always doubly degenerate if is odd. This proof holds in all dimensions with arbitrary lattice structures.
- Received 23 December 2014
- Revised 17 August 2015
DOI:https://doi.org/10.1103/PhysRevB.92.161105
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