Physical systems with gain and loss can be described by a non-Hermitian Hamiltonian,which is degenerated at the exceptional points(EPs).Many new and unexpected features have been explored in the non-Hermitian systems ...Physical systems with gain and loss can be described by a non-Hermitian Hamiltonian,which is degenerated at the exceptional points(EPs).Many new and unexpected features have been explored in the non-Hermitian systems with a great deal of recent interest.One of the most fascinating features is that chiral state conversion appears when one EP is encircled dynamically.Here,we propose an easy-controllable levitated microparticle system that carries a pair of EPs and realize slow evolution of the Hamiltonian along loops in the parameter plane.Utilizing the controllable rotation angle,gain and loss coefficients,we can control the structure,size and location of the loops in situ.We demonstrate that,under the joint action of topological structure of energy surfaces and nonadiabatic transitions,the chiral behavior emerges both along a loop encircling an EP and even along a straight path away from the EP.This work broadens the range of parameter space for the chiral state conversion,and proposes a useful platform to explore the interesting properties of exceptional points physics.展开更多
Fluidics is one of the most historic subjects that are well-established over centuries on the macroscopic scale.In recent years,fluid detection using a number of micro/nano scale devices has been achieved.However,the ...Fluidics is one of the most historic subjects that are well-established over centuries on the macroscopic scale.In recent years,fluid detection using a number of micro/nano scale devices has been achieved.However,the interaction of microfluid and solid devices on micro/nano-meter scale still lacks in-depth research.We demonstrate a practical nanomechanical detector for microfluidics via a string resonator with high Q-factor,suspended over a hole.This device is placed under a jet nozzle with several microns of diameter,and the interaction between the micro-gas flow and the resonator is observed by monitoring the variation of the fundamental frequency and the quality factor.Moreover,we manage to measure the fluctuations of the micro-gas flow on the nanomechanical resonator by means of stochastic resonance.This work manifests a potential platform for detecting dynamical fluid behaviors at microscopic scale for novel fluid physics.展开更多
基金Supported by the Fundamental Research Funds for the Central Universities(Grant No.WK2030000032)the National Key R&D Program of China(Grant No.2018YFA0306600)+1 种基金the CAS(Grant Nos.GJJSTD20170001 and QYZDY-SSW-SLH004)Anhui Initiative in Quantum Information Technologies(Grant No.AHY050000).
文摘Physical systems with gain and loss can be described by a non-Hermitian Hamiltonian,which is degenerated at the exceptional points(EPs).Many new and unexpected features have been explored in the non-Hermitian systems with a great deal of recent interest.One of the most fascinating features is that chiral state conversion appears when one EP is encircled dynamically.Here,we propose an easy-controllable levitated microparticle system that carries a pair of EPs and realize slow evolution of the Hamiltonian along loops in the parameter plane.Utilizing the controllable rotation angle,gain and loss coefficients,we can control the structure,size and location of the loops in situ.We demonstrate that,under the joint action of topological structure of energy surfaces and nonadiabatic transitions,the chiral behavior emerges both along a loop encircling an EP and even along a straight path away from the EP.This work broadens the range of parameter space for the chiral state conversion,and proposes a useful platform to explore the interesting properties of exceptional points physics.
基金Supported by the National Key R&D Program of China(Grant No.2018YFA0306600)the Chinese Academy of Sciences(Grant Nos.GJJSTD20170001 and QYZDY-SSW-SLH004)Anhui Initiative in Quantum Information Technologies(Grant No.AHY050000).
文摘Fluidics is one of the most historic subjects that are well-established over centuries on the macroscopic scale.In recent years,fluid detection using a number of micro/nano scale devices has been achieved.However,the interaction of microfluid and solid devices on micro/nano-meter scale still lacks in-depth research.We demonstrate a practical nanomechanical detector for microfluidics via a string resonator with high Q-factor,suspended over a hole.This device is placed under a jet nozzle with several microns of diameter,and the interaction between the micro-gas flow and the resonator is observed by monitoring the variation of the fundamental frequency and the quality factor.Moreover,we manage to measure the fluctuations of the micro-gas flow on the nanomechanical resonator by means of stochastic resonance.This work manifests a potential platform for detecting dynamical fluid behaviors at microscopic scale for novel fluid physics.
