Parity-time symmetry breaking physics of dissipative Mott insulators

An applied electric field causes dielectric breakdown to an insulator, leading to finite current after the field crosses a certain threshold value. This fact has been understood through the dissipative Landau-Zener tunneling mechanism which is analogous to the Schwinger mechanism for vacuum polarization in Quantum Electrodynamics. However, the problem becomes challenging in case of the correlated Mott insulators.
We propose a parity-time (PT) symmetric non-Hermitian Hubbard model which captures the effect of dissipation plus drive in such systems and solve it using Bethe ansatz for one dimension and dynamical mean-field theory (DMFT) for higher dimensions. We find universal critical insulator-to-metal phase transition, signaled by closing of spectral gap of the insulating phase near the PT-symmetry breaking point. We determine the critical exponents for such phase transitions. The 1-dimensional phase transition bears strong analogy with the vortex insulator-to-metal transition, with the same critical exponent found in a recent experiment on Nb superconducting islands. If time permits, I shall also discuss our recent results where disorder enters into the scenario.

References :

1. Tripathi, Galda, Barman, and Vinokur, Phys. Rev. B 94, 041104(R) (2016).
( arXiv:1510.08355v1)