title: Non-Hermitian degeneracies and unidirectional reflectionless atomic lattices.
abstract: Light propagation in optical lattices of driven cold atoms exhibits non-Hermitian degeneracies when the first-order modulation amplitudes of real and imaginary parts of the probe susceptibility are manipulated to be balanced. At these degeneracies, one may observe complete unidirectional reflectionless light propagation. This strictly occurs with no gain and can be easily tuned and fully reversed as supported by the transfer-matrix calculations and explained via a coupled-mode analysis.
authors.affiliation: Center for Quantum Sciences, Northeast Normal University, Changchun 130117, China.
authors.forename: Jin-Hui
authors.initials: JH
authors.lastname: Wu
authors.affiliation: European Laboratory for Nonlinear Spectroscopy, 50019 Firenze, Italy and Department of Engineering and Information Technology and INO-CNR Sensor Lab, Brescia University, 25133 Brescia, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Artoni
authors.affiliation: Scuola Normale Superiore and CNISM, 56126 Pisa, Italy.
authors.forename: G C
authors.initials: GC
authors.lastname: La Rocca