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Showing papers on "Resonance published in 2017"


Journal ArticleDOI
Yurui Qu1, Qiang Li1, Kaikai Du1, Lu Cai1, Jun Lu1, Min Qiu1 
TL;DR: In this paper, an ultrathin metal-insulator-metal plasmonic metamaterial-based zero-static-power mid-infrared thermal emitter incorporating phase-changing material GST is experimentally demonstrated to dynamically control the thermal emission.
Abstract: Dynamic thermal emission control has attracted growing interest in a broad range of fields, including radiative cooling, thermophotovoltaics and adaptive camouflage. Previous demonstrations of dynamic thermal emission control present disadvantages of either large thickness or requiring sustained electrical or thermal excitations. In this paper, an ultrathin (∼0.023λ, λ is the emission peak wavelength) metal-insulator-metal plasmonic metamaterial-based zero-static-power mid-infrared thermal emitter incorporating phase-changing material GST is experimentally demonstrated to dynamically control the thermal emission. The electromagnetic modes can be continuously tuned through the intermediate phases determined by controlling the temperature. A typical resonance mode, which involves the coupling between the high-order magnetic resonance and anti-reflection resonance, shifts from 6.51 to 9.33 μm while GST is tuned from amorphous to crystalline phase. This demonstration will pave the way towards the dynamical thermal emission control in both the fundamental science field and a number of energy-harvesting applications.

187 citations


Journal ArticleDOI
TL;DR: It is shown thatFerromagnetic resonance caused by injecting SAWs was observed in a Ni-Fe film attached to a Cu film, with the resonance further found to be suppressed through the insertion of a SiO_{2} film into the interface.
Abstract: We demonstrate the generation of alternating spin current (SC) via spin-rotation coupling (SRC) using a surface acoustic wave (SAW) in a Cu film. Ferromagnetic resonance caused by injecting SAWs was observed in a Ni-Fe film attached to a Cu film, with the resonance further found to be suppressed through the insertion of a SiO_{2} film into the interface. The intensity of the resonance depended on the angle between the wave vector of the SAW and the magnetization of the Ni-Fe film. This angular dependence is explicable in terms of the presence of spin transfer torque from a SC generated via SRC.

140 citations


Journal ArticleDOI
TL;DR: An explicit Förster-type expression for the rate of plasmon-coupled resonance energy transfer (PC-RET) is derived and the concept of a generalized spectral overlap (GSO) J̃ is developed for understanding the wavelength dependence of PC-RET.
Abstract: In this study, we overview resonance energy transfer between molecules in the presence of plasmonic structures and derive an explicit Forster-type expression for the rate of plasmon-coupled resonance energy transfer (PC-RET). The proposed theory is general for energy transfer in the presence of materials with any space-dependent, frequency-dependent, or complex dielectric functions. Furthermore, the theory allows us to develop the concept of a generalized spectral overlap (GSO) J (the integral of the molecular absorption coefficient, normalized emission spectrum, and the plasmon coupling factor) for understanding the wavelength dependence of PC-RET and to estimate the rate of PC-RET WET. Indeed, WET = (8.785 × 10–25 mol) ϕDτD–1J, where ϕD is donor fluorescence quantum yield and τD is the emission lifetime. Simulations of the GSO for PC-RET show that the most important spectral region for PC-RET is not necessarily near the maximum overlap of donor emission and acceptor absorption. Instead a significant p...

138 citations


Journal ArticleDOI
TL;DR: In this paper, the authors theoretically and experimentally report subwavelength resonant panels for low-frequency quasiperfect sound absorption including transmission by using the accumulation of cavity resonances due to the slow sound phenomenon.
Abstract: We theoretically and experimentally report subwavelength resonant panels for low-frequency quasiperfect sound absorption including transmission by using the accumulation of cavity resonances due to the slow sound phenomenon. The subwavelength panel is composed of periodic horizontal slits loaded by identical Helmholtz resonators (HRs). Due to the presence of the HRs, the propagation inside each slit is strongly dispersive, with near-zero phase velocity close to the resonance of the HRs. In this slow sound regime, the frequencies of the cavity modes inside the slit are down-shifted and the slit behaves as a subwavelength resonator. Moreover, due to strong dispersion, the cavity resonances accumulate at the limit of the band gap below the resonance frequency of the HRs. Near this accumulation frequency, simultaneously symmetric and antisymmetric quasicritical coupling can be achieved. In this way, using only monopolar resonators quasiperfect absorption can be obtained in a material including transmission.

131 citations


Journal ArticleDOI
TL;DR: In this article, Zhang et al. analyzed the stability of a hypersonic boundary layer on a flared cone for the same flow conditions as in earlier experiments, and the nonlinear parabolized stability equations (NPSE) were used in an extensive parametric study of the interactions between the second mode and the single low-frequency mode (the Gortler mode or the first mode).
Abstract: The stability of a hypersonic boundary layer on a flared cone was analysed for the same flow conditions as in earlier experiments (Zhang et al., Acta Mech. Sinica, vol. 29, 2013, pp. 48–53; Zhu et al., AIAA J., vol. 54, 2016, pp. 3039–3049). Three instabilities in the flared region, i.e. the first mode, the second mode and the Gortler mode, were identified using linear stability theory (LST). The nonlinear-parabolized stability equations (NPSE) were used in an extensive parametric study of the interactions between the second mode and the single low-frequency mode (the Gortler mode or the first mode). The analysis shows that waves with frequencies below 30 kHz are heavily amplified. These low-frequency disturbances evolve linearly at first and then abruptly transition to parametric resonance. The parametric resonance, which is well described by Floquet theory, can be either a combination resonance (for non-zero frequencies) or a fundamental resonance (for steady waves) of the secondary instability. Moreover, the resonance depends only on the saturated state of the second mode and is insensitive to the initial low-frequency mode profiles and the streamwise curvature, so this resonance is probably observable in boundary layers over straight cones. Analysis of the kinetic energy transfer further shows that the rapid growth of the low-frequency mode is due to the action of the Reynolds stresses. The same mechanism also describes the interactions between a second-mode wave and a pair of low-frequency waves. The only difference is that the fundamental and combination resonances can coexist. Qualitative agreement with the experimental results is achieved.

107 citations


Journal ArticleDOI
TL;DR: In this article, a defect-induced planar meta-atom that supports multiple Fano resonances in a defective corrugated metallic disk (CMD) structure is proposed.
Abstract: A novel defect-induced planar meta-atom that supports multiple Fano resonances in a defective corrugated metallic disk (CMD) structure is proposed. Numerical and experimental results reveal that multiple Fano resonances can be excited at terahertz frequencies when the symmetry of the CMD is broken by introducing a small angular defect. These multiple Fano resonances result from mutual coupling between the bright dipolar mode evoked by the edge of the wedge-shaped slice and dark multipole spoof localized surface plasmon modes. Furthermore, the influence of the angle of defect on the Q-factor and the resonance intensity of the quadrupolar resonance peak is investigated. Large values of figure of merit are obtained due to higher Fano resonance intensity and Q-factor. Results from two defective slices in the CMD structure validate the mechanism of the observed phenomenon. The findings of this work would enable a defect-induced Fano resonance platform for biosensing, terahertz domain filtering, and strong light–matter interactions.

106 citations


Journal ArticleDOI
TL;DR: Simulation results indicate that the six-band or nine-band absorber possesses nine distinct resonance bands, and average absorptivities of them are larger than 94.03%.
Abstract: This paper reports on a numerical study of the six-band metamaterial absorber composed of two alternating stack of metallic-dielectric layers on top of a continuous metallic plane. Six obvious resonance peaks with high absorption performance (average larger than 99.37%) are realized. The first, third, fifth, and the second, fourth, sixth resonance absorption bands are attributed to the multiple-order responses (i.e., the 1-, 3- and 5-order responses) of the bottom- and top-layer of the structure, respectively, and thus the absorption mechanism of six-band absorber is due to the combination of two sets of the multiple-order resonances of these two layers. Besides, the size changes of the metallic layers have the ability to tune the frequencies of the six-band absorber. Employing the results, we also present a six-band polarization tunable absorber through varying the sizes of the structure in two orthogonal polarization directions. Moreover, nine-band terahertz absorber can be achieved by using a three-layer stacked structure. Simulation results indicate that the absorber possesses nine distinct resonance bands, and average absorptivities of them are larger than 94.03%. The six-band or nine-band absorbers obtained here have potential applications in many optoelectronic and engineering technology areas.

105 citations


Journal ArticleDOI
TL;DR: The achieved atomic-scale spatial resolution in remote sensing of spins may ultimately allow the structural imaging of individual magnetic molecules, nanostructures and spin-labelled biomolecules.
Abstract: The dipole–dipole magnetic interaction between individual atoms on MgO surfaces is quantified by performing electron spin resonance by means of a scanning tunnelling microscope, opening new paths towards structural imaging with sub-nm resolution. Spin resonance provides the high-energy resolution needed to determine biological and material structures by sensing weak magnetic interactions1. In recent years, there have been notable achievements in detecting2 and coherently controlling3,4,5,6,7 individual atomic-scale spin centres for sensitive local magnetometry8,9,10. However, positioning the spin sensor and characterizing spin–spin interactions with sub-nanometre precision have remained outstanding challenges11,12. Here, we use individual Fe atoms as an electron spin resonance (ESR) sensor in a scanning tunnelling microscope to measure the magnetic field emanating from nearby spins with atomic-scale precision. On artificially built assemblies of magnetic atoms (Fe and Co) on a magnesium oxide surface, we measure that the interaction energy between the ESR sensor and an adatom shows an inverse-cube distance dependence (r−3.01±0.04). This demonstrates that the atoms are predominantly coupled by the magnetic dipole–dipole interaction, which, according to our observations, dominates for atom separations greater than 1 nm. This dipolar sensor can determine the magnetic moments of individual adatoms with high accuracy. The achieved atomic-scale spatial resolution in remote sensing of spins may ultimately allow the structural imaging of individual magnetic molecules, nanostructures and spin-labelled biomolecules.

104 citations


Journal ArticleDOI
TL;DR: It is demonstrated that by driving both modes nonlinearly and electrostatically near the veering regime, such that the first and third modes exhibit softening and hardening behavior, respectively, sharp roll off from the passband to the stopband is achievable.
Abstract: We experimentally demonstrate an exploitation of the nonlinear softening, hardening, and veering phenomena (near crossing), where the frequencies of two vibration modes get close to each other, to realize a bandpass filter of sharp roll off from the passband to the stopband. The concept is demonstrated based on an electrothermally tuned and electrostatically driven MEMS arch resonator operated in air. The in-plane resonator is fabricated from a silicon-on-insulator wafer with a deliberate curvature to form an arch shape. A DC current is applied through the resonator to induce heat and modulate its stiffness, and hence its resonance frequencies. We show that the first resonance frequency increases up to twice of the initial value while the third resonance frequency decreases until getting very close to the first resonance frequency. This leads to the phenomenon of veering, where both modes get coupled and exchange energy. We demonstrate that by driving both modes nonlinearly and electrostatically near the veering regime, such that the first and third modes exhibit softening and hardening behavior, respectively, sharp roll off from the passband to the stopband is achievable. We show a flat, wide, and tunable bandwidth and center frequency by controlling the electrothermal actuation voltage.

82 citations


Journal ArticleDOI
TL;DR: The amplitudes of the combination resonances are quantitatively compared with those of other traditional resonances (e.g. main resonances, harmonics) and the influences of several paramount parameters on nonlinear bubble oscillations are demonstrated.

80 citations


Journal ArticleDOI
TL;DR: In this paper, the authors proposed a low-noise, triply resonant, electro-optic (EO) scheme for quantum microwave-to-optical conversion based on coupled nanophotonics resonators integrated with a superconducting qubit.
Abstract: We propose a low-noise, triply resonant, electro-optic (EO) scheme for quantum microwave-to-optical conversion based on coupled nanophotonics resonators integrated with a superconducting qubit. Our optical system features a split resonance---a doublet---with a tunable frequency splitting that matches the microwave resonance frequency of the superconducting qubit. This is in contrast to conventional approaches, where large optical resonators with free-spectral range comparable to the qubit microwave frequency are used. In our system, EO mixing between the optical pump coupled into the low-frequency doublet mode and a resonance microwave photon results in an up-converted optical photon on resonance with high-frequency doublet mode. Importantly, the down-conversion process, which is the source of noise, is suppressed in our scheme as the coupled-resonator system does not support modes at that frequency. Our device has at least an order of magnitude smaller footprint than conventional devices, resulting in large overlap between optical and microwave fields and a large photon conversion rate ($g/2\ensuremath{\pi}$) in the range of $\ensuremath{\sim}5$--15 kHz. Owing to a large $g$ factor and doubly resonant nature of our device, microwave-to-optical frequency conversion can be achieved with optical pump powers in the range of tens of microwatts, even with moderate values for optical $\mathit{Q}$ ($\ensuremath{\sim}{10}^{6}$) and microwave $Q$ ($\ensuremath{\sim}{10}^{4}$). The performance metrics of our device, with substantial improvement over the previous EO-based approaches, promise a scalable quantum microwave-to-optical conversion and networking of superconducting processors via optical fiber communication.

Journal ArticleDOI
TL;DR: The ability to perform spectroscopy and dynamically monitor spin-dependent redox reactions at these scales enables the development of electron spin resonance and zepto-chemistry in the physical and life sciences.
Abstract: Magnetic resonance spectroscopy is one of the most important tools in chemical and bio-medical research. However, sensitivity limitations typically restrict imaging resolution to ~ 10 µm. Here we bring quantum control to the detection of chemical systems to demonstrate high-resolution electron spin imaging using the quantum properties of an array of nitrogen-vacancy centres in diamond. Our electron paramagnetic resonance microscope selectively images electronic spin species by precisely tuning a magnetic field to bring the quantum probes into resonance with the external target spins. This provides diffraction limited spatial resolution of the target spin species over a field of view of 50 × 50 µm2 with a spin sensitivity of 104 spins per voxel or ∼100 zmol. The ability to perform spectroscopy and dynamically monitor spin-dependent redox reactions at these scales enables the development of electron spin resonance and zepto-chemistry in the physical and life sciences.Electron paramagnetic resonance spectroscopy has important scientific and medical uses but improving the resolution of conventional methods requires cryogenic, vacuum environments. Simpson et al. show nitrogen vacancy centres can be used for sub-micronmetre imaging with improved sensitivity in ambient conditions.

Journal ArticleDOI
TL;DR: A new transmodal Fabry-Pérot resonance where one elastic-wave mode is maximally transmitted to another is discovered where the phase difference of two dissimilar modes through an anisotropic layer becomes odd multiples of π under the reflection-free and weak mode-coupling assumptions.
Abstract: We discovered a new transmodal Fabry-Perot resonance where one elastic-wave mode is maximally transmitted to another. It occurs when the phase difference of two dissimilar modes through an anisotropic layer becomes odd multiples of π under the reflection-free and weak mode-coupling assumptions. Unlike the well-established Fabry-Perot resonance, the transmodal resonance must involve two coupled elastic waves between longitudinal and shear modes. The investigation into the origin of wiggly transmodal transmission spectra suggests that efficient broadband mode conversion can be achieved if the media satisfy the structural stability condition to some degree. The new resonance mechanism, also experimentally characterized, opens up new possibilities for manipulating elastic wave modes as an effective alternative to generating shear-mode ultrasound.

Journal ArticleDOI
TL;DR: Active tuning of quantum size effects in SP resonances supported by a 20-nm-thick metallic film of indium tin oxide (ITO), a plasmonic material serving as a low-carrier-density Drude metal is shown.
Abstract: Surface plasmon (SP) excitations in metals facilitate confinement of light into deep-subwavelength volumes and can induce strong light-matter interaction. Generally, the SP resonances supported by noble metal nanostructures are explained well by classical models, at least until the nanostructure size is decreased to a few nanometres, approaching the Fermi wavelength λF of the electrons. Although there is a long history of reports on quantum size effects in the plasmonic response of nanometre-sized metal particles, systematic experimental studies have been hindered by inhomogeneous broadening in ensemble measurements, as well as imperfect control over size, shape, faceting, surface reconstructions, contamination, charging effects and surface roughness in single-particle measurements. In particular, observation of the quantum size effect in metallic films and its tuning with thickness has been challenging as they only confine carriers in one direction. Here, we show active tuning of quantum size effects in SP resonances supported by a 20-nm-thick metallic film of indium tin oxide (ITO), a plasmonic material serving as a low-carrier-density Drude metal. An ionic liquid (IL) is used to electrically gate and partially deplete the ITO layer. The experiment shows a controllable and reversible blue-shift in the SP resonance above a critical voltage. A quantum-mechanical model including the quantum size effect reproduces the experimental results, whereas a classical model only predicts a red shift.

Journal ArticleDOI
TL;DR: It is shown that a single SDR can be used as an optical nanoantenna that provides strong unidirectional emission from an electric dipole source and achieves the first Kerker condition.
Abstract: Dielectric metasurfaces that exploit the different Mie resonances of nanoscale dielectric resonators are a powerful platform for manipulating electromagnetic fields and can provide novel optical behavior. In this work, we experimentally demonstrate independent tuning of the magnetic dipole resonances relative to the electric dipole resonances of split dielectric resonators (SDRs). By increasing the split dimension, we observe a blue shift of the magnetic dipole resonance toward the electric dipole resonance. Therefore, SDRs provide the ability to directly control the interaction between the two dipole resonances within the same resonator. For example, we achieve the first Kerker condition by spectrally overlapping the electric and magnetic dipole resonances and observe significantly suppressed backward scattering. Moreover, we show that a single SDR can be used as an optical nanoantenna that provides strong unidirectional emission from an electric dipole source.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the temperature-dependent microwave absorption spectrum of an yttrium iron garnet sphere as a function of temperature (5 to $300 ) and frequency (3 to $43.5 ) and showed that the magnetic resonance linewidth increases linearly with temperature and shows a Gilbert-like linear frequency dependence.
Abstract: We investigate the temperature-dependent microwave absorption spectrum of an yttrium iron garnet sphere as a function of temperature (5 to $300\phantom{\rule{4pt}{0ex}}\mathrm{K}$) and frequency (3 to $43.5\phantom{\rule{4pt}{0ex}}\mathrm{GHz}$). At temperatures above $100\phantom{\rule{4pt}{0ex}}\mathrm{K}$, the magnetic resonance linewidth increases linearly with temperature and shows a Gilbert-like linear frequency dependence. At lower temperatures, the temperature dependence of the resonance linewidth at constant external magnetic fields exhibits a characteristic peak which coincides with a non-Gilbert-like frequency dependence. The complete temperature and frequency evolution of the linewidth can be modeled by the phenomenology of slowly relaxing rare-earth impurities and either the Kasuya-LeCraw mechanism or the scattering with optical magnons. Furthermore, we extract the temperature dependence of the saturation magnetization, the magnetic anisotropy, and the $g$ factor.

Journal ArticleDOI
TL;DR: In this article, the twisted omega particle has been realized as a 3D chiral meta-atom, which consists of a loop-wire structure, leading to the separation of right-handed circularly polarized light and the left-handed one.
Abstract: The plasmonic version of a 3D chiral meta-atom which consists of a loop-wire structure, namely the so-called twisted omega particle, is experimentally realized. The structure is fabricated by direct laser writing and subsequent electroless silver plating, a novel technique capable of producing truly 3D photonic nanostructures. In this case, the metallic wire of finite length supports an electric dipole resonance, whereas the loop acts as a split-ring resonator which exhibits a magnetic dipole resonance, leading to the separation of right-handed circularly polarized light and the left-handed one. The arising optical activity is discussed in terms of a single oscillator model system used classically to describe the generation of natural optical activity in chiral media, and it is shown that the twisted omega particle acts as its exact plasmonic analogue.

Journal ArticleDOI
25 Jun 2017-Sensors
TL;DR: A plasmonic waveguide coupled system that uses a metal-insulator-metal (MIM) waveguide with two silver baffles and a coupled ring cavity with a maximum sensitivity of 718 nm/RIU and the maximum figure of merit of 4354 is proposed in this study.
Abstract: A plasmonic waveguide coupled system that uses a metal-insulator-metal (MIM) waveguide with two silver baffles and a coupled ring cavity is proposed in this study. The transmission properties of the plasmonic system were investigated using the finite element method. The simulation results show a Fano profile in the transmission spectrum, which was caused by the interaction of the broadband resonance of the Fabry-Perot (F-P) cavity and the narrow band resonance of the ring cavity. The Fabry-Perot (F-P) cavity in this case was formed by two silver baffles dividing the MIM waveguide. The maximum sensitivity of 718 nm/RIU and the maximum figure of merit of 4354 were achieved. Furthermore, the effects of the structural parameters of the F-P cavity and the ring cavity on the transmission properties of the plasmonic system were analyzed. The results can provide a guide for designing highly sensitive on-chip sensors based on surface plasmon polaritons.

Journal ArticleDOI
TL;DR: Coupling of magnetically trapped ultracold Rb ground-state atoms to a coherently driven superconducting coplanar resonator on an integrated atom chip enables the preparation of coherent atomic superposition states, which are required for the implementation of an atomic quantum memory.
Abstract: Ensembles of trapped atoms interacting with on-chip microwave resonators are considered as promising systems for the realization of quantum memories, novel quantum gates, and interfaces between the microwave and optical regime. Here, we demonstrate coupling of magnetically trapped ultracold Rb ground-state atoms to a coherently driven superconducting coplanar resonator on an integrated atom chip. When the cavity is driven off-resonance from the atomic transition, the microwave field strength in the cavity can be measured through observation of the AC shift of the atomic hyperfine transition frequency. When driving the cavity in resonance with the atoms, we observe Rabi oscillations between hyperfine states, demonstrating coherent control of the atomic states through the cavity field. These observations enable the preparation of coherent atomic superposition states, which are required for the implementation of an atomic quantum memory.

Journal ArticleDOI
TL;DR: In this paper, photonic crystal nanobeam cavities with rectangular cross section were fabricated into bulk diamond and measured cavity resonances showed fundamental modes with spectrometer-limited Q factors ≥ 14×103 within 1'nm of the nitrogen vacancy centers zero phonon line at 637'nm.
Abstract: We demonstrate the fabrication of photonic crystal nanobeam cavities with rectangular cross section into bulk diamond. In simulation, these cavities have an unloaded quality (Q) factor of over 1 × 106. Measured cavity resonances show fundamental modes with spectrometer-limited Q factors ≥14×103 within 1 nm of the nitrogen vacancy centers zero phonon line at 637 nm. We find high cavity yield across the full diamond chip with deterministic resonance trends across the fabricated parameter sweeps.

Journal ArticleDOI
TL;DR: In this paper, the topological properties of a strongly coupled spin-photon system induced by damping were examined and it was shown that the boundary between weak and strong coupling should be based on the exceptional point (EP), rather than the cooperativity.
Abstract: We experimentally examine the topological nature of a strongly coupled spin-photon system induced by damping The presence of both spin and photonic losses results in a non-Hermitian system with a variety of exotic phenomena dictated by the topological structure of the eigenvalue spectra and the presence of an exceptional point (EP), where the coupled spin-photon eigenvectors coalesce By controlling both the spin resonance frequency and the spin-photon coupling strength we observe a resonance crossing for cooperativities above one, suggesting that the boundary between weak and strong coupling should be based on the EP location rather than the cooperativity Furthermore, we observe dynamic mode switching when encircling the EP and identify the potential to engineer the topological structure of coupled spin-photon systems with additional modes Our work therefore further highlights the role of damping within the strong coupling regime, and demonstrates the potential and great flexibility of spin-photon systems for studies of non-Hermitian physics

Journal ArticleDOI
TL;DR: In this paper, a sharp resonance in the tunnelling spectrum of a two-dimensional electron system was found to arise from vibrational modes, not involving ionic motion, but instead arising from vibrations of spatial ordering of the electrons themselves.
Abstract: Resonances in the tunnelling spectra of a two-dimensional electron system provide strong evidence that the electrons arrange themselves into a Wigner crystal lattice with long-range ordering. Photoemission and tunnelling spectroscopies measure the energies at which single electrons can be added to or removed from an electronic system1. Features observed in such spectra have revealed electrons coupling to vibrational modes of ions both in solids2 and in individual molecules3. Here we report the discovery of a sharp resonance in the tunnelling spectrum of a two-dimensional electron system. Its behaviour suggests that it originates from vibrational modes, not involving ionic motion, but instead arising from vibrations of spatial ordering of the electrons themselves. In a two-dimensional electronic system at very low temperatures and high magnetic fields, electrons can either condense into a variety of quantum Hall phases or arrange themselves into a highly ordered ‘Wigner’ crystal lattice4,5,6. Such spatially ordered phases of electrons are often electrically insulating and delicate, and have proven very challenging to probe with conventional methods. Using a pulsed tunnelling method capable of probing electron tunnelling into insulating phases, we observe a sharp peak with dependencies on energy and other parameters that fit to models for vibrations of a Wigner crystal7,8. The remarkable sharpness of the structure presents strong evidence of the existence of a Wigner crystal with long correlation length.

Journal ArticleDOI
TL;DR: In this article, strong optical nonlinearity of monolayer MoS2(1-x)Se2x was investigated across the exciton resonance, which is directly tunable by Se doping.
Abstract: We have investigated strong optical nonlinearity of monolayer MoS2(1–x)Se2x across the exciton resonance, which is directly tunable by Se doping. The quality of monolayer alloys prepared by chemical vapor deposition is verified by atomic force microscopy, Raman spectroscopy, and photoluminescence analysis. The crystal symmetry of all of our alloys is essentially D3h, as confirmed by polarization-dependent second-harmonic generation (SHG). The spectral structure of the exciton resonance is sampled by wavelength-dependent SHG (λ = 1000–1800 nm), where the SHG resonance red-shifts in accordance with the corresponding optical gap. Surprisingly, the effect of compositional variation turns out to be much more dramatic owing to the unexpected increase of B-exciton-induced SHG, which indeed dominates over the A-exciton resonance for x ≥ 0.3. The overall effect is therefore stronger and broader SHG resonance where the latter arises from different degrees of red-shift for the two exciton states. We report the corre...

Journal ArticleDOI
TL;DR: Control dielectric gradient forces tune the resonance frequencies of the flexural in-plane and out-of-plane oscillation of the high stress silicon nitride string through their mutual avoided crossing to observe locking phenomena of two strongly coupled, high quality factor nanomechanical resonator modes to a common parametric drive.
Abstract: We study locking phenomena of two strongly coupled, high quality factor nanomechanical resonator modes to a common parametric drive at a single drive frequency in different parametric driving regimes. By controlled dielectric gradient forces we tune the resonance frequencies of the flexural in-plane and out-of-plane oscillation of the high stress silicon nitride string through their mutual avoided crossing. For the case of the strong common parametric drive signal-idler generation via nondegenerate parametric two-mode oscillation is observed. Broadband frequency tuning of the very narrow linewidth signal and idler resonances is demonstrated. When the resonance frequencies of the signal and idler get closer to each other, partial injection locking, injection pulling, and complete injection locking to half of the drive frequency occurs depending on the pump strength. Furthermore, satellite resonances, symmetrically offset from the signal and idler by their beat note, are observed, which can be attributed to degenerate four-wave mixing in the highly nonlinear mechanical oscillations.

Journal ArticleDOI
TL;DR: In this paper, quantum Monte-Carlo calculations of few-neutron systems confined in external potentials based on local chiral interactions at next to next-to-leading order in chiral effective field theory are presented.
Abstract: We present quantum Monte Carlo calculations of few-neutron systems confined in external potentials based on local chiral interactions at next-to-next-to-leading order in chiral effective field theory. The energy and radial densities for these systems are calculated in different external Woods-Saxon potentials. We assume that their extrapolation to zero external-potential depth provides a quantitative estimate of three- and four-neutron resonances. The validity of this assumption is demonstrated by benchmarking with an exact diagonalization in the two-body case. We find that the extrapolated trineutron resonance, as well as the energy for shallow well depths, is lower than the tetraneutron resonance energy. This suggests that a three-neutron resonance exists below a four-neutron resonance in nature and is potentially measurable. To confirm that the relative ordering of three- and four-neutron resonances is not an artifact of the external confinement, we test that the odd-even staggering in the helium isotopic chain is reproduced within this approach. Finally, we discuss similarities between our results and ultracold Fermi gases.

Journal ArticleDOI
TL;DR: The interaction of the toroidal dipolar resonance with monolayer graphene further highlights the ultrasensitive sensing characteristic of the planar metamaterial, which can be utilized for other graphene-like two-dimensional materials.
Abstract: A planar terahertz metamaterial consisting of square split ring resonators is proposed, and the excitation of toroidal dipolar resonance is demonstrated. Moreover, we theoretically investigate the strong interaction between graphene and toroidal dipolar resonance of the metamaterial. By varying its Fermi energy, the simulations show that graphene can actively modulate the transmission amplitude of toroidal dipolar resonance and even switch it off. The interaction of the toroidal dipolar resonance with monolayer graphene further highlights the ultrasensitive sensing characteristic of the planar metamaterial, which can be utilized for other graphene-like two-dimensional materials. These intriguing properties of the proposed metamaterial may have potential applications in terahertz modulators and ultrasensitive sensors.

Journal ArticleDOI
TL;DR: This work opens up a new concept to design and fabricate the up-conversion core-shell structure based on semiconductor plasmon nanoparticles (NPs) and provides applications for up- Conversion nanocrystals (UCNPs), semiconductor Plasmon NPs in photonics.
Abstract: The ability to modulate the intensity of electromagnetic field by semiconductor plasmon nanoparticles is becoming attractive due to its unique doping-induced local surface plasmon resonance (LSPR) effect that is different from metals. Herein, we synthesized mCu2–xS@SiO2@Y2O3:Yb3+/Er3+ core–shell composites and experimentally and theoretically studied the semiconductor plasmon induced up-conversion enhancement and obtained 30-fold up-conversion enhancement compared with that of SiO2@Y2O3:Yb3+/Er3+ composites. The up-conversion enhancement was induced by the synthetic effect: the amplification of the excitation field and the increase of resonance energy transfer (ET) rate from Yb3+ ions to Er3+ ions. The experimental results were analyzed in the light of finite-difference time-domain (FDTD) calculations, confirming the effect of the amplification of the excitation field. In addition, up-conversion luminescence (UCL) spectra, up-conversion enhancement, and dynamics dependent on concentration (Yb3+ and Er3+ i...

Journal ArticleDOI
TL;DR: Applying angle-resolved electron spectroscopy, a large photon helicity dependence of the spectrum and the angular distribution of the electrons ejected from the resonance by NIR multiphoton absorption are found.
Abstract: Intense, circularly polarized extreme-ultraviolet and near-infrared (NIR) laser pulses are combined to double ionize atomic helium via the oriented intermediate He^{+}(3p) resonance state. Applying angle-resolved electron spectroscopy, we find a large photon helicity dependence of the spectrum and the angular distribution of the electrons ejected from the resonance by NIR multiphoton absorption. The measured circular dichroism is unexpectedly found to vary strongly as a function of the NIR intensity. The experimental data are well described by theoretical modeling and possible mechanisms are discussed.

Journal ArticleDOI
Gui-Dong Liu1, Xiang Zhai1, Sheng-Xuan Xia1, Qi Lin1, Chujun Zhao1, Ling-Ling Wang1 
TL;DR: Numerical simulation results show that the transmission amplitude of the toroidal dipolar resonance can be efficiently modulated by varying the Fermi energy EF when the graphene layer is integrated with the dielectric metasurface, and a max transmission coefficient difference up to 78% is achieved indicating that the proposed hybrid graphene/dielectric meetasurfaces shows good performance as an optical modulator.
Abstract: In this paper, we demonstrate the combination of a dielectric metasurface with a graphene layer to realize a high performance toroidal resonance based optical modulator. The dielectric metasurface consists of two mirrored asymmetric silicon split-ring resonators (ASSRRs) that can support strong toroidal dipolar resonance with narrow line width (~0.77 nm) and high quality (Q)-factor (~1702) and contrast ratio (~100%). Numerical simulation results show that the transmission amplitude of the toroidal dipolar resonance can be efficiently modulated by varying the Fermi energy EF when the graphene layer is integrated with the dielectric metasurface, and a max transmission coefficient difference up to 78% is achieved indicating that the proposed hybrid graphene/dielectric metasurface shows good performance as an optical modulator. The effects of the asymmetry degree of the ASSRRs on the toroidal dipolar resonance are studied and the efficiency of the transmission amplitude modulation of graphene is also investigated. Our results may also provide potential applications in optical filter and bio-chemical sensing.

Journal ArticleDOI
Haiyu Meng1, Ling-Ling Wang1, Gui-Dong Liu1, Xiongxiong Xue1, Qi Lin1, Xiang Zhai1 
TL;DR: The design approaches enable us to control the number of absorption spectra and such absorbers will benefit the easy-to-fabricate nanophotonic devices for optical filtering, thermal detectors, and electromagnetic wave energy storage.
Abstract: We numerically investigate the optical performance of a periodically patterned H-shaped graphene array by the finite-difference time-domain (FDTD) in the mid-infrared region. The simulated results reveal that absorption spectra of the proposed structure consist of two dramatic narrowband perfect absorption peaks located at 6.3 μm (Mode 1) and 8.6 μm (Mode 2) with high absorption coefficients of 99.65% and 99.80%, respectively. Two impressive absorption bandwidths that are the full width at half-maximum (FWHM) of the resonant frequency of 90 nm and 188 nm are obtained. The dipole resonance mode is supported by graphene ribbon at a wavelength of 6.3 μm. While the other absorption, attributed to the hybridized mode, is a new resonance that is different from the dipole resonance. The spectral position of the absorption peaks can be dynamically tuned by controlling the refractive index of the dielectric and the Fermi energy of graphene. Furthermore, we can obtain multispectral absorption peaks by applying multilayer graphene arrays. These design approaches enable us to control the number of absorption spectra and such absorbers will benefit the easy-to-fabricate nanophotonic devices for optical filtering, thermal detectors, and electromagnetic wave energy storage.