Experimental Observation of PT Symmetry Breaking near Divergent Exceptional Points

M. Sakhdari, University of Illinois at Chicago
M. Hajizadegan, University of Illinois at Chicago
Q. Zhong, Michigan Technological University
D. N. Christodoulides, University of Central Florida
R. El-Ganainy, Michigan Technological University
P. Y. Chen, University of Illinois at Chicago

© 2019 American Physical Society. Publisher’s version of record: https://doi.org/10.1103/PhysRevLett.123.193901


Standard exceptional pStandard oints (EPs) are non-Hermitian degeneracies that occur in open systems. At an EP, the Taylor series expansion becomes singular and fails to converge - a feature that was exploited for several applications. Here, we theoretically introduce and experimentally demonstrate a new class of parity-time symmetric systems [implemented using radio frequency (rf) circuits] that combine EPs with another type of mathematical singularity associated with the poles of complex functions. These nearly divergent exceptional points can exhibit an unprecedentedly large eigenvalue bifurcation beyond those obtained by standard EPs. Our results pave the way for building a new generation of telemetering and sensing devices with superior performance.