Correlations at PT-symmetric quantum critical point

Understand

We consider a PT-symmetric Fermi gas with an exceptional point, representing the critical point between PT-symmetric and symmetry broken phases.

• The low energy spectrum remains linear in momentum and is identical to that of a hermitian Fermi gas.
• The fermionic Green's function decays in a power law fashion for large distances, as expected from gapless excitations, albeit the exponent is reduced from $-1$ due to the quantum Zeno effect.
• In spite of the gapless nature of the excitations, the ground state entanglement entropy saturates to a finite value, independent of the subsystem size due to the non-hermitian correlation length intrinsic to the system.