The non-Hermitian skin effect has been applied in multiple fields.However,there are relatively few models in the field of thermal diffusion that utilize the non-Hermitian skin effect for achieving thermal regulation.H...The non-Hermitian skin effect has been applied in multiple fields.However,there are relatively few models in the field of thermal diffusion that utilize the non-Hermitian skin effect for achieving thermal regulation.Here,we propose two non-Hermitian Su-Schrieffer-Heeger(SSH)models for thermal regulation:one capable of achieving edge states,and the other capable of achieving corner states within the thermal field.By analyzing the energy band structures and the generalized Brillouin zone,we predict the appearance of the non-Hermitian skin effect in these two models.Furthermore,we analyze the time-dependent evolution results and assess the robustness of the models.The results indicate that the localized thermal effects of the models align with our predictions.In a word,this work presents two models based on the non-Hermitian skin effect for regulating the thermal field,injecting vitality into the design of non-Hermitian thermal diffusion systems.展开更多
The super-cell plane wave expansion method is employed to calculate band structures for the design of a siliconbased one-dimensional phononic crystal plate with large absolute forbidden bands. In this method, a low im...The super-cell plane wave expansion method is employed to calculate band structures for the design of a siliconbased one-dimensional phononic crystal plate with large absolute forbidden bands. In this method, a low impedance medium is introduced to replace the free stress boundary, which largely reduces the computational complexity. The dependence of band gaps on structural parameters is investigated in detail. To prove the validity of the super-cell plane wave expansion, the transmitted power spectra of the Lamb wave are calculated by using a finite element method. With the detailed computation, the band-gap of a one-dimensional plate can be designed as required with appropriate structural parameters, which provides a guide to the fabrication of a Lamb wave phononic crystal.展开更多
We propose a multi-layer structure for concealing an electromagnetic sensing system (a sensor is wrapped witha transparent protective layer),using single-negative (SNG) materials whose material parameters are complete...We propose a multi-layer structure for concealing an electromagnetic sensing system (a sensor is wrapped witha transparent protective layer),using single-negative (SNG) materials whose material parameters are completely independent of those of the host matrix as well as the concealed system.The numerical results show that only three different kinds of SNG materials are sufficient to yield the cloaking effect even in the presence of weak loss.This may significantly facilitate the experimental realization of a well-performing sensor-cloaking device.展开更多
We propose a design of tunable double-band perfect absorbers based on the resonance absorption in acoustic metasurfaces with nesting helical tracks and deep-subwavelength thicknesses(<λ/30 withλbeing the operatio...We propose a design of tunable double-band perfect absorbers based on the resonance absorption in acoustic metasurfaces with nesting helical tracks and deep-subwavelength thicknesses(<λ/30 withλbeing the operation wavelength).By rotating the cover cap with an open aperture on the nesting helical tracks,we can tailor the effective lengths of resonant tubular cavities in the absorber at will,while the absorption peak frequency is flexibly shifted in spectrum and the acoustic impedance is roughly matched with air.The simulated particle velocity fields at different configurations reveal that sound absorption mainly occurs at the open aperture.Our experiment measurements agree well with the theoretical analysis and simulation,demonstrating the wide-spectrum and tunable absorption performance of the designed flat acoustic device.展开更多
Since the first observation of parity-time（PT） symmetry in optics, varied interesting phenomena have been discovered in both theories and experiments, such as PT phase transition and unidirectional invisibility, whi...Since the first observation of parity-time（PT） symmetry in optics, varied interesting phenomena have been discovered in both theories and experiments, such as PT phase transition and unidirectional invisibility, which turns PT-symmetric optics into a hotspot in research. Here, we report on the one-way localized Fabry-Pérot（FP） resonance, where a welldesigned PT optical resonator may operate at exceptional points with bidirectional transparency but unidirectional field localization. Overtones of such one-way localized FP resonance can be classified into a blue shifted branch and a red shifted branch. Therefore, the fundamental resonant frequency is not the lowest one. We find that the spatial field distributions of the overtones at the same absolute order are almost the same, even though their frequencies are quite different.展开更多
Acoustic bands are studied numerically for a Lamb wave propagating in an anti-symmetric structure of a one- dimensional periodic plate by using the method of supercell plane-wave expansion. The results show that all t...Acoustic bands are studied numerically for a Lamb wave propagating in an anti-symmetric structure of a one- dimensional periodic plate by using the method of supercell plane-wave expansion. The results show that all the bands are pinned in pairs at the Brillouin zone boundary as long as the anti-symmetry remains and acoustic band gaps （ABGs） only appear between certain bands. In order to reveal the relationship between the band pinning and the anti-symmetry, the method of eigenmode analysis is introduced to calculate the displacement fields of different plate structures. Further, the method of harmony response analysis is employed to calculate the reference spectra to verify the accuracy of numerical calculations of acoustic band map, and both the locations and widths of ABGs in the acoustic band map are in good agreement with those of the reference spectra. The investigations show that the pinning effect is very sensitive to the anti-symmetry of periodic plates, and by introducing different types of breakages, more ABGs or narrow pass bands will appear, which is meaningful in band gap engineering.展开更多
Parity-time (PT) symmetry/anti-parity-time (APT) symmetry in non-Hermitian systems reveal profound physics andspawn intriguing effects. Recently, it has been introduced into diffusive systems together with the concept...Parity-time (PT) symmetry/anti-parity-time (APT) symmetry in non-Hermitian systems reveal profound physics andspawn intriguing effects. Recently, it has been introduced into diffusive systems together with the concept of exceptionalpoints (EPs) from quantum mechanics and the wave systems. With the aid of convection, we can generate complex thermalconductivity and imitate various wavelike dynamics in heat transfer, where heat flow can be “stopped” or moving against thebackground motion. Non-Hermitian diffusive systems offer us a new platform to investigate the heat wave manipulation.In this review, we first introduce the construction of APT symmetry in a simple double-channel toy model. Then we showthe phase transition around the EP. Finally, we extend the double-channel model to the four-channel one for showing thehigh-order EP and the associated phase transition. In a general conclusion, the phase difference of adjacent channels isalways static in the APT symmetric phase, while it dynamically evolves or oscillates when the APT symmetry is broken.展开更多
We explore the exceptional point(EP)induced phase transition and amplitude/phase modulation in thermal diffusion systems.We start from the asymmetric coupling double-channel model,where the temperature field is unbala...We explore the exceptional point(EP)induced phase transition and amplitude/phase modulation in thermal diffusion systems.We start from the asymmetric coupling double-channel model,where the temperature field is unbalanced in the amplitude and locked in the symmetric phase.By extending into the one-dimensional tight-binding non-Hermitian lattice,we study the convection-driven phase locking and the asymmetric-couplinginduced diffusive skin effect with the high-order EPs in static systems.Combining convection and asymmetric couplings,we further show the phase-locking diffusive skin effect.Our work reveals the mechanism of controlling both the amplitude and phase of temperature fields in thermal coupling systems and has potential applications in non-Hermitian topology in thermal diffusion.展开更多
The paradigm shift of Hermitian systems into the non-Hermitian regime profoundly modifies inherent property of the topological systems, leading to various unprecedented effects such as the nonHermitian skin effect(NHS...The paradigm shift of Hermitian systems into the non-Hermitian regime profoundly modifies inherent property of the topological systems, leading to various unprecedented effects such as the nonHermitian skin effect(NHSE). In the past decade, the NHSE has been demonstrated in quantum, optical and acoustic systems. Beside those wave systems, the NHSE in diffusive systems has not yet been observed, despite recent abundant advances in the study of topological thermal diffusion. In this work,we design a thermal diffusion lattice based on a modified Su-Schrieffer-Heeger model and demonstrate the diffusive NHSE. In the proposed model, the asymmetric temperature field coupling inside each unit cell can be judiciously realized by appropriate configurations of structural parameters. We find that the temperature fields trend to concentrate toward the target boundary which is robust against initial excitation conditions. We thus experimentally demonstrated the NHSE in thermal diffusion and verified its robustness against various defects. Our work provides a platform for exploration of non-Hermitian physics in the diffusive systems, which has important applications in efficient heat collection, highly sensitive thermal sensing and others.展开更多
基金Supported by National Natural Science Foundation of China (No .60577040) Shanghai Foundation of Applied Ma-terials Research and Development ( No .0404) +1 种基金Nano-technology Project of Shanghai ( No .0452nm051 , No .0552nm046) Shanghai Leading Academic Disciplines (No .T0101)
基金the National Natural Science Foundation of China (60577040)Shanghai Foundation of Applied Materials Research and Development (0404)+1 种基金Nano-technology project of Shanghai (0452nm051,0552nm046)Shanghai Leading Academic Disciplines (T0101) .
基金Supported by National Natural Science Foundation of China (No .60577040)Shanghai Foundation of Applied Ma-terials Research and Development ( No .0404)+1 种基金 Nano-technology Project of Shanghai ( No .0452nm051 , No .0552nm046)Shanghai Leading Academic Disciplines (No .T0101)
基金supported by the Key Research and Development Program of China(Grant No.2022YFA1405200)the National Natural Science Foundation of China(Grant Nos.92163123 and 52250191)。
文摘The non-Hermitian skin effect has been applied in multiple fields.However,there are relatively few models in the field of thermal diffusion that utilize the non-Hermitian skin effect for achieving thermal regulation.Here,we propose two non-Hermitian Su-Schrieffer-Heeger(SSH)models for thermal regulation:one capable of achieving edge states,and the other capable of achieving corner states within the thermal field.By analyzing the energy band structures and the generalized Brillouin zone,we predict the appearance of the non-Hermitian skin effect in these two models.Furthermore,we analyze the time-dependent evolution results and assess the robustness of the models.The results indicate that the localized thermal effects of the models align with our predictions.In a word,this work presents two models based on the non-Hermitian skin effect for regulating the thermal field,injecting vitality into the design of non-Hermitian thermal diffusion systems.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10874086 and 10834009)the National Basic Research Program of China (Grant No. 2010CB327803)
文摘The super-cell plane wave expansion method is employed to calculate band structures for the design of a siliconbased one-dimensional phononic crystal plate with large absolute forbidden bands. In this method, a low impedance medium is introduced to replace the free stress boundary, which largely reduces the computational complexity. The dependence of band gaps on structural parameters is investigated in detail. To prove the validity of the super-cell plane wave expansion, the transmitted power spectra of the Lamb wave are calculated by using a finite element method. With the detailed computation, the band-gap of a one-dimensional plate can be designed as required with appropriate structural parameters, which provides a guide to the fabrication of a Lamb wave phononic crystal.
基金Supported by the National Basic Research Program of China under Grant No 2011CB707900the National Natural Science Foundation of China under Grant Nos 10804050,10874086,10834009 and 10904068.
文摘We propose a multi-layer structure for concealing an electromagnetic sensing system (a sensor is wrapped witha transparent protective layer),using single-negative (SNG) materials whose material parameters are completely independent of those of the host matrix as well as the concealed system.The numerical results show that only three different kinds of SNG materials are sufficient to yield the cloaking effect even in the presence of weak loss.This may significantly facilitate the experimental realization of a well-performing sensor-cloaking device.
基金National Natural Science Foundation of China(Grant Nos.1167434611704284+2 种基金11690030and 11690032)Bird Nest Plan of HUST。
文摘We propose a design of tunable double-band perfect absorbers based on the resonance absorption in acoustic metasurfaces with nesting helical tracks and deep-subwavelength thicknesses(<λ/30 withλbeing the operation wavelength).By rotating the cover cap with an open aperture on the nesting helical tracks,we can tailor the effective lengths of resonant tubular cavities in the absorber at will,while the absorption peak frequency is flexibly shifted in spectrum and the acoustic impedance is roughly matched with air.The simulated particle velocity fields at different configurations reveal that sound absorption mainly occurs at the open aperture.Our experiment measurements agree well with the theoretical analysis and simulation,demonstrating the wide-spectrum and tunable absorption performance of the designed flat acoustic device.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674119,11404125,and 11574389)the financial support from the Bird Nest Plan of HUST,Chinasupported by One Hundred-Talent Plan of Chinese Academy of Sciences
文摘Since the first observation of parity-time（PT） symmetry in optics, varied interesting phenomena have been discovered in both theories and experiments, such as PT phase transition and unidirectional invisibility, which turns PT-symmetric optics into a hotspot in research. Here, we report on the one-way localized Fabry-Pérot（FP） resonance, where a welldesigned PT optical resonator may operate at exceptional points with bidirectional transparency but unidirectional field localization. Overtones of such one-way localized FP resonance can be classified into a blue shifted branch and a red shifted branch. Therefore, the fundamental resonant frequency is not the lowest one. We find that the spatial field distributions of the overtones at the same absolute order are almost the same, even though their frequencies are quite different.
基金supported by the National Basic Research Program of China(Grant No.2010CB327803)the National Natural Science Foundation of China(Grant Nos.10874086,10834009,and 10904068)+1 种基金the Science Foundation of the Ministry of Education of China(Grant No.705017)the Fundamental Research Funds for the Central Universities,China(Grant No.1085020401)
文摘Acoustic bands are studied numerically for a Lamb wave propagating in an anti-symmetric structure of a one- dimensional periodic plate by using the method of supercell plane-wave expansion. The results show that all the bands are pinned in pairs at the Brillouin zone boundary as long as the anti-symmetry remains and acoustic band gaps （ABGs） only appear between certain bands. In order to reveal the relationship between the band pinning and the anti-symmetry, the method of eigenmode analysis is introduced to calculate the displacement fields of different plate structures. Further, the method of harmony response analysis is employed to calculate the reference spectra to verify the accuracy of numerical calculations of acoustic band map, and both the locations and widths of ABGs in the acoustic band map are in good agreement with those of the reference spectra. The investigations show that the pinning effect is very sensitive to the anti-symmetry of periodic plates, and by introducing different types of breakages, more ABGs or narrow pass bands will appear, which is meaningful in band gap engineering.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674119 and 11690032)the Fundamental Research Funds for the Central Universities,China(HUST:2019JYCXJJ038)X.F.Z.and P.C.C.acknowledge the financial support from the Bird Nest Plan of HUST.
文摘Parity-time (PT) symmetry/anti-parity-time (APT) symmetry in non-Hermitian systems reveal profound physics andspawn intriguing effects. Recently, it has been introduced into diffusive systems together with the concept of exceptionalpoints (EPs) from quantum mechanics and the wave systems. With the aid of convection, we can generate complex thermalconductivity and imitate various wavelike dynamics in heat transfer, where heat flow can be “stopped” or moving against thebackground motion. Non-Hermitian diffusive systems offer us a new platform to investigate the heat wave manipulation.In this review, we first introduce the construction of APT symmetry in a simple double-channel toy model. Then we showthe phase transition around the EP. Finally, we extend the double-channel model to the four-channel one for showing thehigh-order EP and the associated phase transition. In a general conclusion, the phase difference of adjacent channels isalways static in the APT symmetric phase, while it dynamically evolves or oscillates when the APT symmetry is broken.
基金supported by the National Natural Science Foundation of China(Grant Nos.92163123,11690030,and 11690032)。
文摘We explore the exceptional point(EP)induced phase transition and amplitude/phase modulation in thermal diffusion systems.We start from the asymmetric coupling double-channel model,where the temperature field is unbalanced in the amplitude and locked in the symmetric phase.By extending into the one-dimensional tight-binding non-Hermitian lattice,we study the convection-driven phase locking and the asymmetric-couplinginduced diffusive skin effect with the high-order EPs in static systems.Combining convection and asymmetric couplings,we further show the phase-locking diffusive skin effect.Our work reveals the mechanism of controlling both the amplitude and phase of temperature fields in thermal coupling systems and has potential applications in non-Hermitian topology in thermal diffusion.
基金supported by the National Key Research and Development Program of China (2023YFB4604100, and 2023YFB4604800)the National Natural Science Foundation of China (92163123, 12304492, and 52250191)+1 种基金Zhejiang Provincial Natural Science Foundation of China (LZ24A050002)the China Postdoctoral Science Foundation (2023M733120)。
文摘The paradigm shift of Hermitian systems into the non-Hermitian regime profoundly modifies inherent property of the topological systems, leading to various unprecedented effects such as the nonHermitian skin effect(NHSE). In the past decade, the NHSE has been demonstrated in quantum, optical and acoustic systems. Beside those wave systems, the NHSE in diffusive systems has not yet been observed, despite recent abundant advances in the study of topological thermal diffusion. In this work,we design a thermal diffusion lattice based on a modified Su-Schrieffer-Heeger model and demonstrate the diffusive NHSE. In the proposed model, the asymmetric temperature field coupling inside each unit cell can be judiciously realized by appropriate configurations of structural parameters. We find that the temperature fields trend to concentrate toward the target boundary which is robust against initial excitation conditions. We thus experimentally demonstrated the NHSE in thermal diffusion and verified its robustness against various defects. Our work provides a platform for exploration of non-Hermitian physics in the diffusive systems, which has important applications in efficient heat collection, highly sensitive thermal sensing and others.
