Parity-time-reversal symmetry-breaking transitions in polymeric systems.

We show that classical DNA unzipping transition, which is equivalently described by quantum mechanical localization-delocalization transition in the ground state of non-Hermitian single impurity Hatano-Nelson Hamiltonian, is underpinned by generalized parity (P)-time reversal (T) symmetry breaking transition. We also study one-dimensional discretized version of the Hatano-Nelson model in the presence of single impurity and random disorder on a finite-size lattice. These discrete models are useful to study unzipping of a single adsorbed polymer from a surface. Our results show that the discrete models also undergo a phase transition from a PT unbroken phase to a broken phase. Interestingly, the generalized PT phase transition points coincide with the localization-delocalization transition for continuum as well as lattice models.