[1] A. Mostafazadeh. Physics of spectral singularities. Geometric Methods in Physics, 145-165(2015).
[4] E. Teller. The crossing of potential surfaces. J. Phys. Chem., 41, 109-116(1937).
[7] T. Kato. Perturbation Theory for Linear Operators, 132(2013).
[8] N. Moiseyev. Non-Hermitian Quantum Mechanics(2011).
[22] H. A. Haus, W. Huang. Coupled-mode theory. Proc. IEEE, 79, 1505-1518(1991).
[23] The most general non-Hermitian coupled mode theory could involve complex coupling coefficients [24]. In our heterostructure (involving two defect layers), however, the modeling of Eq. (1) is sufficient for capturing all transport features (see Section 3).
[32] D. Christodoulides, J. Yang. Parity-Time Symmetry and Its Applications, 280(2018).