Derek D. Scott, Yogesh N. Joglekar

We investigate the robustness of parity- and time-reversal PT-symmetric phase in an N-site lattice with position-dependent, parity-symmetric hopping function and a pair of imaginary, PT-symmetric impurities. We find that the “fragile” PT-symmetric phase in these lattices is stronger than its counterpart in a lattice with constant hopping. With an open system in mind, we explore the degrees of broken PT symmetry and their signatures in single-particle wavepacket evolution. We predict that when the PT-symmetric impurities are closest to each other, the time evolution of a wavepacket in an even-N lattice is remarkably different from that in an odd-$N$ lattice. Our results suggest that PT-symmetry breaking in such lattices is accompanied by rich, hitherto unanticipated, phenomena.

http://arxiv.org/abs/1104.1666

Quantum Physics (quant-ph); Quantum Gases (cond-mat.quant-gas)