Extended SSH Model in Non-Hermitian Waveguides with Alternating Real and Imaginary Couplings

We studied the topological properties of an extended Su–Schrieffer–Heeger (SSH) model composed of a binary waveguide array with alternating real and imaginary couplings. The topological invariant of the periodic structures remained quantized with chiral symmetry even though the system was non-Hermitian. The numerical results indicated that phase transition arose when the absolute values of the two couplings were equal. The system supported a topological zero mode at the boundary of nontrivial structures when chiral symmetry was preserved. By adding onsite gain and loss to break chiral symmetry, the topological modes dominated in all supermodes with maximum absolute value of imaginary energy. This study enriches research on the SSH model in non-Hermitian systems and may find applications in optical routers and switches.

A dynamical mass and confinement in nucleon model

A possible dynamical softening of the Chiral bag is studied in connection with the chiral quark model and the Nambu–Jona–Lasinio (NJL) model. It is demonstrated that the bag functions constructed by the pion degrees is able to confine quark through generation of the rising effective mass of valence quark due to the pion dressing and break chiral symmetry dynamically. The tendency of the bag functions toward the MIT bag is illustrated in the large-n limit for a solitonic configuration of the chiral field Un(r) for which U1(r) is the Skyrmion profile. The mass running with the length scale agrees with that of the NJL Model for n ≥ 2.