Parity-Time (PT) symmetry is an emerging concept in quantum mechanics where non-Hermitian Hamiltonians can exhibit real eigenvalues. Now, PT symmetric optical microresonators have been demonstrated to break the bandwidth-efficiency limit for nonlinear optical signal processing.
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http://dx.doi.org/10.1038/s41377-024-01577-0 | DOI Listing |
Phys Rev Lett
December 2024
School of Physics and Electronics, Hunan University, Changsha 410082, China.
Electron-hole exchange interaction in two-dimensional transition metal dichalcogenides is extremely strong due to the dimension reduction, which promises valley-superposed excitonic states with linearly polarized optical emissions. However, strong circular polarization reflecting valley-polarized excitonic states is commonly observed in helicity-resolved optical experiments. Here, we present a non-Hermitian theory of valley excitons by incorporating optical pumping and intrinsic decay, which unveils an anomalous valley-polarized excitonic state with elliptically polarized optical emission.
View Article and Find Full Text PDFJ Phys Condens Matter
December 2024
Department of Physics, AKPC Mahavidyalaya, Bengai, West Bengal 712611, India.
We study the effect of periodic hopping modulation in a Su-Schrieffer-Heeger (SSH) chain with an additional onsite staggered imaginary potential (of strength). Such dissipative, non-Hermitian (NH) extension amply modifies the features of the topological trivial phase (TTP) and the topological nontrivial phase (TNP) of the SSH chain, more so with the periodic hopping distribution. Generally a weak NH potential can respect the parity-time (PT) symmetry keeping the energy eigenvalues real, while a strong potential breaksPTconservation leading to imaginary edge state and complex bulk state energies in the system.
View Article and Find Full Text PDFSci Rep
November 2024
Guangdong Provincial Key Laboratory of Nanophotonic Functional Materials and Devices, School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou, 510006, China.
In this study, we propose a superior coherent perfect absorber and laser (CPA laser) constructed from the one-dimensional (1D) two-material (TM) parity-time (PT) symmetric periodic ring optical waveguide network (PROWN). A novel method based on seeking the exact extremum spontaneous PT-symmetric breaking points is used for determining the imaginary part of the refractive indices of the materials composed of waveguides. The minimal overall output coefficient [Formula: see text] and maximal transmissivity [Formula: see text] can reach [Formula: see text] and [Formula: see text], respectively, which are 9 orders of magnitude smaller and larger than the previously reported values, respectively.
View Article and Find Full Text PDFNat Commun
November 2024
Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA, USA.
Exceptional points in non-Hermitian systems have attracted considerable attention due to their novel applications in several fields such as optics, electronics, and mechanics. Typically, exceptional points are constructed through gain and loss modulation or dissipative coupling within the framework of parity-time symmetry or anti-parity-time symmetry. Recent demonstration of unidirectional coupling in optical resonators to create exceptional points has offered an alternative approach.
View Article and Find Full Text PDFSensors (Basel)
October 2024
Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing 210096, China.
With the rapid development in sensor network technology, the complexity and diversity of application scenarios have put forward more and more new requirements for inductor-capacitor () sensors, for instance, multi-parameter simultaneous monitoring. Here, the parity-time (PT) symmetry concept in quantum mechanics is applied to passive wireless sensing. Two or even three parameters can be monitored simultaneously by observing the frequency response of the reflection coefficient at the end of the readout circuit.
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