Nonreciprocal Effects Research Articles

Integrated Photonic Nonreciprocal Devices Based on Susceptibility‐Programmable Medium

AbstractThe switching and control of optical fields based on nonlinear optical effects are often limited by relatively weak nonlinear susceptibility, which requiring strong optical pump fields. Here, an optical medium with programmable susceptibility tensor based on polarizable atoms is proposed. Under a structured optical pump, the population of atoms in the ground state could be efficiently controlled by tuning the chirality and intensity of optical fields, and thus the optical response of the medium is programmable in both space and time. The potential of this approach is demonstrated by engineering the spatial distribution of the complex susceptibility tensor of the medium in photonic structures, which enables the realization of nonreciprocal optical effects. Specifically, the advantages of chiral interaction between atoms and photons are investigated in an atom‐cladded waveguide, theoretically showing that strong, rapidly switchable, and reconfigurable isolation of optical signals in a selected optical mode is possible. The susceptibility‐programmable medium provides a promising way to efficiently control the optical field, opening up a wide range of applications for integrated photonic devices and structured optics.

Automated design of nonreciprocal thermal emitters via Bayesian optimization

Nonreciprocal thermal emitters that break Kirchhoff’s law of thermal radiation promise exciting applications for thermal and energy applications. The design of the bandwidth and angular range of the nonreciprocal effect, which directly affects the performance of nonreciprocal emitters, typically relies on physical intuition. In this study, we present a general numerical approach to maximize the nonreciprocal effect. We choose doped magneto-optic materials and magnetic Weyl semimetal materials as model materials and focus on pattern-free multilayer structures. The optimization randomly starts from a less effective structure and incrementally improves the broadband nonreciprocity through the combination of Bayesian optimization and reparameterization. Optimization results show that the proposed approach can discover structures that can achieve broadband nonreciprocal emission at wavelengths from 5 to 40 μm using only a fewer layers, significantly outperforming current state-of-the-art designs based on intuition in terms of both performance and simplicity.

A wavelength-division-multiplex depolarized Sagnac-based interferometer for noise suppression

The Sagnac-based interferometer (SI) has been developed over several decades and is widely recognized for its sensitivity and stability. Most SIs utilize polarization-maintaining (PM) fiber and polarizers to ensure polarization reciprocity, or depolarizers to mitigate the effects of polarization non-reciprocity. The depolarizing method was considered more promising from a marketability standpoint. Additionally, broadband optical sources were typically used in SIs to eliminate the Kerr effect and backscatter. However, broadband light source SIs are hindered by high excess relative intensity noise (excess RIN) generated by the self-interference of different spectral components. To enhance the performance of SIs, it is crucial to suppress the excess RIN. In this study, we demonstrate a wavelength-division-multiplex depolarized Sagnac-based interferometer and suppress the excess RIN by utilizing the overlap of two interfering lights, which shifts the primary frequency of noise outside the detection range. Experimental results show that the noise equivalent displacement at a light intensity of 42 μW achieves 170.18 fm/√Hz, which encompasses both shot noise and non-optical noise, indicating successful suppression of excess RIN.

Magneto-optical Particles in Isotropic Spinning Fields Mimic Magnetic Monopoles.

In contrast with the typical electric currents accelerated under the influence of a Coulombic force, there are only a few condensed matter examples of particles experiencing a force proportional to a constant, external magnetic field. In this Letter, we present a new alternative, based on an isotropic radiation spinning field and the magneto-optical effect, in which a particle is propelled by a magnetic field just like a magnetic monopole will do. This is a purely nonreciprocal effect as the reciprocal equivalent (a chiral dipole), despite presenting a dichroic response, does not experience any force when illuminated by the spinning field. The "magnetic charge" induced by impinging radiation on the magneto-optical dipole is found to depend linearly on the helicity of the field. In addition, this artificial monopole experiences a dichroic permanent optical torque and does not interact with an external electric field.

Picosecond Trajectory of Two-Dimensional Vortex Motion in FeSe_{0.5}Te_{0.5} Visualized by Terahertz Second Harmonic Generation.

We have investigated the vortex dynamics in a thin film of an iron-based superconductor FeSe_{0.5}Te_{0.5} by observing second-harmonic generation (SHG) in the terahertz frequency range. We visualized the picosecond trajectory of two-dimensional vortex motion in a pinning potential tilted by Meissner shielding current. The SHG perpendicular to the driving field is observed, corresponding to the nonreciprocal nonlinear Hall effect under the current-induced inversion symmetry breaking, whereas the linear Hall effect is negligible. The estimated vortex mass, as light as a bare electron, suggests that the vortex core moves independently from quasiparticles at such a high frequency and large velocity ≈300 km/s.

Two-dimensional Su-Schrieffer-Heeger model with imaginary potentials and nonreciprocal couplings

We examine the 2D-SSH model and focus on its topological states and skin effects resulting from imaginary potentials and nonreciprocal couplings. Our calculations demonstrate that inducing topological edge and corner states allows for different topological phase transitions in the 2D-SSH model. The topological phase transition is achieved by adjusting the ratio of the intercell electron hopping to the intracell electron hopping. The PT symmetry of the system is destroyed when an imaginary potential is present. If non-reciprocal effects are introduced, then skin effects will be seen. This work contributes to understanding how the interplay between imaginary potentials and nonreciprocal couplings modulates the skin effects and topological states in 2D-SSH model.

Tunable nonreciprocal thermal emitter based on graphene/indium arsenide/silver microstructure

Nonreciprocal thermal radiation has been studied by people. However, previous research has mainly focused on TM waves. Therefore, this article investigates a nonreciprocal transmitter based on TE transverse waves. Nonreciprocal emitters completely violate Kirchhoff's law and can be applied to various thermal radiation devices. However, there is little research on tunable nonreciprocal thermal emitters. In this article, we innovatively replace the previous top metal grating structure with a graphene grating. The gate voltage of graphene can regulate the nonreciprocal radiation intensity of the device in this article, without the need to resimulate the structure, and can achieve tunable strong nonreciprocal radiation effects. When the incident angle is 30°, the azimuth angle is 72° and the external magnetic field is 3 T, the thermal emitter can obtain strong nonreciprocal thermal radiation at a wavelength of about 16.6 μm. The difference between emissivity and absorptivity is greater than 0.91, indicating the presence of significant strong nonreciprocal radiation. We explained the physical background of this effect by studying the electromagnetic field distribution at the resonance peak.

Relations between normal state nonreciprocal transport and the superconducting diode effect in the trivial and topological phases

Nonreciprocal transport effects can occur in the normal state of conductors and in superconductors when both inversion and time-reversal symmetry are broken. Here, we consider systems where magnetochiral anisotropy of the energy spectrum due to an externally applied magnetic field results in a rectification effect in the normal state and a superconducting (SC) diode effect when the system is proximitized by a superconductor. Focusing on nanowire systems, we obtain analytic expressions for both normal state rectification and SC diode effects that reveal the commonalities—as well as differences—between these two phenomena. Furthermore, we consider the nanowire brought into an (almost) helical state in the normal phase or a topological SC phase when proximitized. In both cases, this reveals that the topology of the system considerably modifies its nonreciprocal transport properties. Our results provide insights into how to determine the origin of nonreciprocal effects and further evince the strong connection of nonreciprocal transport with the topological properties of a system.

Giant and nonreciprocal photonic spin hall effect in asymmetric multilayered structure with bulk dirac semimetal

Abstract The nonreciprocal photonic spin Hall effect features the different reflected or transmitted spin shifts along two opposite incident wave propagating directions. However, previous investigations have always focused on the features of the photonic spin Hall effect along one incident wave propagating direction. How to achieve the nonreciprocal photonic spin Hall effect remains obscure. Here, we theoretically study the nonreciprocal photonic spin Hall effect in the asymmetric multilayered structure containing the Bulk Dirac Semimetal and other dielectric materials. It is found that under the horizontal polarization the maximum reflected spin shift value along one direction is up to around times of the incident wavelength at , but it is only times of the incident wavelength at along the other direction, which reflects the nonreciprocity of photonic spin Hall effect and thus can act as the photonic spin Hall diode. Such a sizeable directional difference between the reflected spin shifts along these two opposite directions originates from the fact that this structure loses its mirror symmetry and becomes an asymmetrical one, and the obvious difference in the values of the reflected spin shifts along the two directions can be attributed to the large difference in the values of . At the same time, we find that the Fermi energy of the Bulk Dirac Semimetal can effectively tune the spin shift along the backward direction, as well as the difference between the spin shifts for two different propagating directions, which causes the controllable nonreciprocal photonic spin Hall effect. Our results establish the alternative configuration for realizing the nonreciprocal photonic spin Hall effect, which facilitates the potential applications in the spin photonic devices.

Programmable nonreciprocal Poynting effect enabled by lattice metamaterials.

Shear nonreciprocity, implying unequal shear forces in opposite shear directions, can be achieved by arranging structures asymmetrically. However, the nonreciprocal Poynting effect, i.e., unequal normal stresses induced by the same shear displacements to the left and right, has not been fully explored. We discover the nonreciprocal Poynting effect using a generalized directional truss model. Inspired by this discovery, the cylindrical lattice metamaterials constructed from antisymmetric curled microstructures are used as a case study to generate the nonreciprocal Poynting effect. We develop a design framework that integrates digital generation, finite deformation theory, finite element modeling, and three-dimensional printing to program the nonreciprocal Poynting effect. Applications such as bionic Poynting effect matching, wave energy converter, and unidirectional motion limitation are demonstrated. This framework allows the one-to-one mapping between the torque and normal forces, paving the way for designing soft devices with precise force transmission capabilities.

Electrical switching of Ising-superconducting nonreciprocity for quantum neuronal transistor

Nonreciprocal quantum transport effect is mainly governed by the symmetry breaking of the material systems and is gaining extensive attention in condensed matter physics. Realizing electrical switching of the polarity of the nonreciprocal transport without external magnetic field is essential to the development of nonreciprocal quantum devices. However, electrical switching of superconducting nonreciprocity remains yet to be achieved. Here, we report the observation of field-free electrical switching of nonreciprocal Ising superconductivity in Fe3GeTe2/NbSe2 van der Waals (vdW) heterostructure. By taking advantage of this electrically switchable superconducting nonreciprocity, we demonstrate a proof-of-concept nonreciprocal quantum neuronal transistor, which allows for implementing the XOR logic gate and faithfully emulating biological functionality of a cortical neuron in the brain. Our work provides a promising pathway to realize field-free and electrically switchable nonreciprocity of quantum transport and demonstrate its potential in exploring neuromorphic quantum devices with both functionality and performance beyond the traditional devices.

Superconducting Diode Effect in a Constricted Nanowire

AbstractDue to isotropic superconducting properties and the lack of breaking of inversion symmetry for conventional s‐wave superconductors, a nonreciprocal superconducting diode effect is absent. Recently, a series of superconducting structures, including superconducting superlattice, and quantum‐material‐based superconducting Josephson junction, have exhibited a superconducting diode effect in terms of polarity‐dependent critical current. However, due to complex structures, these composite systems are not able to construct large‐scale integrated superconducting circuits. Here, it is demonstrated that the minimal superconducting electric component‐superconducting nanowire‐based diode with a nonreciprocal transport effect under a perpendicular magnetic field, in which the superconducting to normal metallic phase transition relies on the polarity and amplitude of the bias current. These nanowire diodes can be reliably operated near at all temperatures below the critical temperature, and the rectification efficiency at 2 K can be more than 24%. Moreover, the superconducting nanowire diode is able to rectify both square wave and sine wave signals. Combining the superconducting nanowire‐based diodes and transistors, superconducting nanowires hold the possibility to construct novel low‐dissipation superconducting integrated circuits.

Nonreciprocal Unconventional Photon Blockade with Kerr Magnons

AbstractNonreciprocal devices, allowing to manipulate one‐way signals, are crucial to quantum information processing and quantum networks. Here a nonlinear cavity‐magnon system is proposed, consisting of a microwave cavity coupled to one or two yttrium–iron–garnet (YIG) spheres supporting magnons with Kerr nonlinearity, to investigate nonreciprocal unconventional photon blockade. The nonreciprocity originates from the direction‐dependent Kerr effect, distinctly different from previous proposals with spinning cavities and dissipative couplings. For a single sphere case, nonreciprocal unconventional photon blockade can be realized by manipulating the nonreciprocal destructive interference between two active paths, via varying the Kerr coefficient from positive to negative, or vice versa. By optimizing the system parameters, the perfect and well‐tuned nonreciprocal unconventional photon blockade can be predicted. For the case of two spheres with opposite Kerr effects, only reciprocal unconventional photon blockade can be observed when two cavity‐magnon coupling strengths Kerr strengths are symmetric. However, when coupling strengths or Kerr strengths become asymmetric, nonreciprocal unconventional photon blockade appears. This implies that two‐sphere nonlinear cavity‐magnon systems can be used to switch the transition between reciprocal and nonreciprocal unconventional photon blockades. This study offers a potential platform for investigating the nonreciprocal photon blockade effect in nonlinear cavity magnonics.

Magnetic Nonreciprocity in a Hybrid Device of Asymmetric Artificial Spin-Ice-Superconductors

Controlling the size and distribution of potential barriers within a medium of interacting particles can unveil unique collective behaviors and innovative functionalities. We introduce a unique superconducting hybrid device using a novel artificial spin ice structure composed of asymmetric nanomagnets. This structure forms a distinctive superconducting pinning potential that steers unconventional motion of superconducting vortices, thereby inducing a magnetic nonreciprocal effect, in contrast to the electric nonreciprocal effect commonly observed in superconducting diodes. Furthermore, the polarity of the magnetic nonreciprocity is in situ reversible through the tunable magnetic patterns of artificial spin ice. Our findings demonstrate that artificial spin ice not only precisely modulates superconducting characteristics but also opens the door to novel functionalities, offering a groundbreaking paradigm for superconducting electronics.

Experimental demonstration of non-reciprocity effects on satellite-based two-way time-frequency transfer links

Experimental demonstration of non-reciprocity effects on satellite-based two-way time-frequency transfer links

Wide-angle and Fano-shape contrast between emission and absorption in hybrid polariton-involved planar structure

Nonreciprocal light propagation in planar structure has become a hot topic because of the pattern-free fabrication process and the potentials for exploring heat transfer and energy management. An effective strategy incorporated with natural van der Waals material (α-phase molybdenum trioxide, α-MoO3), ultra-thin polar crystal (silicon carbide, SiC) thin film and a Weyl semimetal interlayer sitting on a metal (silver, Ag) substrate is proposed. The emission and absorption of the suggested device is explored with electromagnetic simulations that utilize the 4×4 transfer matrix method. Angular-resolved emission shows that the Fano-shape of nonreciprocity can be maintained within wide angle range. Tunable Fano resonances with different line shapes are demonstrated by varying the structural parameters. Moreover, the enhanced nonreciprocal radiation effect can be observed for both s- and p-polarized incidence waves. The proposal allows simultaneous control of spectral distribution and polarization of radiation, which will facilitate the active design and application of mid-infrared emitters.

Phase Transition to Chaos in Complex Ecosystems with Nonreciprocal Species-Resource Interactions.

Nonreciprocal interactions between microscopic constituents can profoundly shape the large-scale properties of complex systems. Here, we investigate the effects of nonreciprocity in the context of theoretical ecology by analyzing a generalization of MacArthur's consumer-resource model with asymmetric interactions between species and resources. Using a mixture of analytic cavity calculations and numerical simulations, we show that such ecosystems generically undergo a phase transition to chaotic dynamics as the amount of nonreciprocity is increased. We analytically construct the phase diagram for this model and show that the emergence of chaos is controlled by a single quantity: the ratio of surviving species to surviving resources. We also numerically calculate the Lyapunov exponents in the chaotic phase and carefully analyze finite-size effects. Our findings show how nonreciprocal interactions can give rise to complex and unpredictable dynamical behaviors even in the simplest ecological consumer-resource models.

Nonlinear and Nonreciprocal Transport Effects in Untwinned Thin Films of Ferromagnetic Weyl Metal SrRuO3

The identification of distinct charge transport features, deriving from nontrivial bulk band and surface states, has been a challenging subject in the field of topological systems. In topological Dirac and Weyl semimetals, nontrivial conical bands with Fermi-arc surface states give rise to negative longitudinal magnetoresistance due to chiral anomaly effect and unusual thickness dependent quantum oscillation from Weyl-orbit effect, which were demonstrated recently in experiments. In this work, we report the experimental observations of large nonlinear and nonreciprocal transport effects for both longitudinal and transverse channels in an untwinned Weyl metal of SrRuO3 thin film grown on a SrTiO3 substrate. From rigorous measurements with bias current applied along various directions with respect to the crystalline principal axes, the magnitude of nonlinear Hall signals from the transverse channel exhibits a simple sinα dependence at low temperatures, where α is the angle between bias current direction and orthorhombic [001]o, reaching a maximum when current is along orthorhombic [11¯0]o. On the contrary, the magnitude of nonlinear and nonreciprocal signals in the longitudinal channel attains a maximum for bias current along [001]o, and it vanishes for bias current along [11¯0]o. The observed α-dependent nonlinear and nonreciprocal signals in longitudinal and transverse channels reveal a magnetic Weyl phase with an effective Berry curvature dipole along [11¯0]o from surface states, accompanied by 1D chiral edge modes along [001]o. Published by the American Physical Society 2024

Nonreciprocal charge-density-wave proximity effect in a lateral heterojunction of NbSe2/TiSe2

Lateral heterostructures between two-dimensional (2D) transition metal dichalcogenides are highly interesting since they have potential applications for constructing monolayer electronic devices. Such in-plane heterostructures are also ideal systems for exploring the interfacial effects on quantum phases, such as charge-density wave (CDW) order in the true 2D limit. Here, we report on a lateral CDW heterojunction made of monolayer NbSe2 and TiSe2 with atomically sharp interface. Scanning tunneling microscopy reveals an unexpectedly nonreciprocal CDW proximity effect at the NbSe2 vicinity of the heterojunctions: the (2 × 2) CDW order of TiSe2 is found to propagate into the NbSe2 side of the heterostructure, while the (3 × 3) CDW order of NbSe2 resides in the NbSe2 side. Such a nonreciprocal CDW proximity effect indicates that the quantum phase of electrons in NbSe2 can be easily tuned by the adjacent TiSe2. Our study highlights the significance of quantum interfacial effect in lateral heterojunctions, which may help for constructing tunable 2D in-plane quantum devices based on proximity effects or in-plane interfaces.

Optical Tellegen metamaterial with spontaneous magnetization

The nonreciprocal magnetoelectric effect, also known as the Tellegen effect, promises a number of groundbreaking phenomena connected to fundamental (e.g., electrodynamics of axion and relativistic matter) and applied physics (e.g., magnetless isolators). We propose a three-dimensional metamaterial with an isotropic and resonant Tellegen response in the visible frequency range. The metamaterial is formed by randomly oriented bi-material nanocylinders in a host medium. Each nanocylinder consists of a ferromagnet in a single-domain magnetic state and a high-permittivity dielectric operating near the magnetic Mie-type resonance. The proposed metamaterial requires no external magnetic bias and operates on the spontaneous magnetization of the nanocylinders. By leveraging the emerging magnetic Weyl semimetals, we further show how a giant bulk effective magnetoelectric effect can be achieved in a proposed metamaterial, exceeding that of natural materials by almost four orders of magnitude.