Coalescence of nonreciprocal exceptional points in magnetized PT -symmetric systems

2018 ◽  
Vol 97 (1) ◽  
Author(s):  
Jin Wang ◽  
Hui Yuan Dong ◽  
Qian Yi Shi ◽  
Wenyan Wang ◽  
Kin Hung Fung
Keyword(s):  
Exceptional Points ◽  
Symmetric Systems

Fourth order exceptional points with spinning resonators

2022 ◽  
Author(s):  
Haoye Qin ◽  
Yiheng Yin ◽  
Ming Ding
Keyword(s):  
Fourth Order ◽  
Light Propagation ◽  
High Efficiency ◽  
Optical Resonators ◽  
Second Order ◽  
Exceptional Points ◽  
Enhanced Sensitivity ◽  
Order Case ◽  
Symmetric Systems

Abstract Investigation of exceptional points mostly focuses on the second order case and employs the gain-involved parity-time (PT) symmetric systems. Here, we propose an approach to implementing fourth order exceptional points (FOEPs) using directly coupled optical resonators with rotation. On resonance, the system manifests FOEP through tuning the spinning velocity to targeted values. Eigenfrequency bifurcation and enhanced sensitivity for nanoparticle have been presented. Also, near FOEP, nonreciprocal light propagation exhibits great boost and dramatic change, which may be applied to high-efficiency isolators and circulators.

scholarly journals EXCEPTIONAL POINTS IN OPEN AND PT-SYMMETRIC SYSTEMS

2014 ◽  
Vol 54 (2) ◽  
pp. 106-112 ◽  
Author(s):  
Hichem Eleuch ◽  
Ingrid Rotter
Keyword(s):  
Open Quantum Systems ◽  
Level Density ◽  
Quantum Systems ◽  
Point Of View ◽  
Eigenvalues And Eigenfunctions ◽  
Open Quantum ◽  
Exceptional Points ◽  
Characteristic Features ◽  
High Level ◽  
Symmetric Systems

Exceptional points (EPs) determine the dynamics of open quantum systems and cause also PT symmetry breaking in PT symmetric systems. From a mathematical point of view, this is caused by the fact that the phases of the wavefunctions (eigenfunctions of a non-Hermitian Hamiltonian) relative to one another are not rigid when an EP is approached. The system is therefore able to align with the environment to which it is coupled and, consequently, rigorous changes of the system properties may occur. We compare analytically as well as numerically the eigenvalues and eigenfunctions of a 2 × 2 matrix that is characteristic either of open quantum systems at high level density or of PT symmetric optical lattices. In both cases, the results show clearly the influence of the environment on the system in the neighborhood of EPs. Although the systems are very different from one another, the eigenvalues and eigenfunctions indicate the same characteristic features.

scholarly journals Rotation-time symmetry in bosonic systems and the existence of exceptional points in the absence of $${\mathscr{PT}}$$ symmetry

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Ewelina Lange ◽  
Grzegorz Chimczak ◽  
Anna Kowalewska-Kudłaszyk ◽  
Karol Bartkiewicz
Keyword(s):  
Symmetry Breaking ◽  
General Type ◽  
Energy Spectra ◽  
Exceptional Points ◽  
Rotation Time ◽  
Time Symmetry ◽  
Laser Pumping ◽  
Special Cases ◽  
New Applications ◽  
Symmetric Systems

AbstractWe study symmetries of open bosonic systems in the presence of laser pumping. Non-Hermitian Hamiltonians describing these systems can be parity-time ($${{\mathscr{PT}}}$$ PT ) symmetric in special cases only. Systems exhibiting this symmetry are characterised by real-valued energy spectra and can display exceptional points, where a symmetry-breaking transition occurs. We demonstrate that there is a more general type of symmetry, i.e., rotation-time ($${\mathscr{RT}}$$ RT ) symmetry. We observe that $${\mathscr{RT}}$$ RT -symmetric non-Hermitian Hamiltonians exhibit real-valued energy spectra which can be made singular by symmetry breaking. To calculate the spectra of the studied bosonic non-diagonalisable Hamiltonians we apply diagonalisation methods based on bosonic algebra. Finally, we list a versatile set rules allowing to immediately identifying or constructing $${\mathscr{RT}}$$ RT -symmetric Hamiltonians. We believe that our results on the $${\mathscr{RT}}$$ RT -symmetric class of bosonic systems and their spectral singularities can lead to new applications inspired by those of the $${{\mathscr{PT}}}$$ PT -symmetric systems.

scholarly journals Exceptional points in oligomer chains

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Charles Andrew Downing ◽  
Vasil Arkadievich Saroka
Keyword(s):  
Open Systems ◽  
Light Transport ◽  
Coupled Modes ◽  
Exceptional Points ◽  
Time Symmetry ◽  
Degree Of Coherence ◽  
Quantum Objects ◽  
Long Range Interactions ◽  
And Control ◽  
Symmetric Systems

AbstractSymmetry underpins our understanding of physical law. Open systems, those in contact with their environment, can provide a platform to explore parity-time symmetry. While classical parity-time symmetric systems have received a lot of attention, especially because of the associated advances in the generation and control of light, there is much more to be discovered about their quantum counterparts. Here we provide a quantum theory which describes the non-Hermitian physics of chains of coupled modes, which has applications across optics and photonics. We elucidate the origin of the exceptional points which govern the parity-time symmetry, survey their signatures in quantum transport, study their influence for correlations, and account for long-range interactions. We also find how the locations of the exceptional points evolve as a function of the chain length and chain parity, capturing how an arbitrary oligomer chain transitions from its unbroken to broken symmetric phase. Our general results provide perspectives for the experimental detection of parity-time symmetric phases in one-dimensional arrays of quantum objects, with consequences for light transport and its degree of coherence.

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