Ernest GrodnerMicha? KowalczykJulian SrebrnyLeszek Próchniak...
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查看更多>>摘要：We present results of a series of experiments aimed at finding the most direct fingerprints of a phenomenon of nuclear chirality.These experi-ments brought a detailed knowledge of the so called partner bands in 132La,128Cs and 126Cs including absolute values of E2 and M1 transition proba-bilities obtained through the DSA(Doppler Shift Attenuation)method.Considering the indirect character of observables such as energies and transition rates we proposed measurement of the g-factor of a chosen state as a direct,ultimate test of chirality.Our experiment on the bandhead of partner bands in 128Cs showed feasibility of this approach.Measured value of the g-factor which suggests non-chiral character of this state leads to another puzzle in the chirality studies—how the chirality emerges with increasing spin of levels along a partner band.
查看更多>>摘要：Recently,it was found that the vector field can be naturally localized on the thick brane in chameleon gravity.In this work,we extend this study to encompass de Sitter brane scenario.We focus on the localization of q-form fields.The scalar and vector fields can be localized on the de Sitter brane,while the KR field cannot be localized.The condition for localization of the scalar and vector fields is obtained.Furthermore,we investigate the localization characteristics in two examples with given conformal factor b(ψ).In the first case,the effective potentials and KK modes of the matter fields are obtained asymmetric even though the de Sitter brane has Z2 symmetry.In the second case,volcano-like effective potentials are gener-ated in the de Sitter brane model.
查看更多>>摘要：Two-dimensional(2D)materials exhibit exceptionally strong nonlinear optical responses,benefiting from their reduced dimensionality,relaxed phase-matching requirements,and enhanced light-matter interaction.With additional degrees of freedom in the modulation of the physical properties by stacking 2D layers together,nonlinear optics of 2D heterostructures becomes increasingly fascinating.In this perspective,we provide a brief overview of recent advances in the field of nonlinear optics of 2D heterostructures,with a particular focus on their remarkable capa-bilities in characterization and modulation.Given the recent advances and the emergence of novel heterostructures,combined with innovative tuning knobs and advanced nonlinear optical techniques,we anticipate deeper insights into the underlying mechanisms and more associated applications in this rapidly evolving field.
查看更多>>摘要：Two-dimensional hafnium-based semiconductors and their heterostruc-tures with native oxides have been shown unique physical properties and potential electronic and optoelectronic applications.However,the scalable synthesis methods for ultrathin layered hafnium-based semiconductor laterally epitaxy growth and its heterostructure are still restricted,also for the understanding of its formation mechanism.Herein,we report the stable sublimation of alkali halide vapor assisted synthesis strategy for high-quality 2D HfSe2 nanosheets via chemical vapor deposition.Single-crystalline ultrathin 2D HfSe2 nanosheets were systematically grown by tuning the growth parameters,reaching the lateral size of 6-40 μm and the thickness down to 4.5 nm.The scalable amorphous HfO2 and HfSe2 heterostructures were achieved by the controllable oxidation,which bene-fited from the approximate zero Gibbs free energy of unstable 2D HfSe2 templates.The crystal structure,elemental,and time dependent Raman characterization were carried out to understand surface precipitated Se atoms and the formation of amorphous Hf-O bonds,confirming the slow surface oxidation and lattice incorporation of oxygen atoms.The relatively smooth surface roughness and electrical potential change of HfO2-HfSe2 heterostructures indicate the excellent interface quality,which helps obtain the high performance memristor with high on/off ratio of 105 and long retention period over 9000 s.Our work introduces a new vapor cata-lysts strategy for the synthesis of lateral 2D HfSe2 nanosheets,also providing the scalable oxidation of the Hf-based heterostructures for 2D electronic devices.
查看更多>>摘要：A unique feature of non-Hermitian systems is the extreme sensitivity of the eigenspectrum to boundary conditions with the emergence of the non-Hermitian skin effect(NHSE).A NHSE originates from the point-gap topology of complex eigenspectrum,where an extensive number of eigen-states are anomalously localized at the boundary driven by nonreciprocal dissipation.Two different approaches to create localization are disorder and flat-band spectrum,and their interplay can lead to the anomalous inverse Anderson localization,where the Bernoulli anti-symmetric disorder induces mobility in a full-flat band system in the presence of Aharonov-Bohm(AB)Cage.In this work,we study the localization-delo-calization transitions due to the interplay of the point-gap topology,flat band and correlated disorder in the one-dimensional rhombic lattice,where both its Hermitian and non-Hermitian structures show AB cage in the presence of magnetic flux.Although it remains the coexistence of localization and delocalization for the Hermitian rhombic lattice in the presence of the random anti-symmetric disorder,it surprisingly becomes complete delocalization,accompanied by the emergence of NHSE.To further study the effects from the Bernoulli anti-symmetric disorder,we found the similar NHSE due to the interplay of the point-gap topology,correlated disorder and flat bands.Our anomalous localization-delocal-ization property can be experimentally tested in the classical physical plat-form,such as electrical circuit.
查看更多>>摘要：As an intrinsic magnetic topological insulator with magnetic order and non-trivial topological structure,MnBi2Te4 is an ideal material for studying exotic topological states such as quantum anomalous Hall effect and topo-logical axion insulating states.Here,we carry out magnetic and electrical transport measurements on(Mn1-xGex)Bi2Te4(x=0,0.15,0.30,0.45,0.60,and 0.75)single crystals.It is found that with increasing x,the dilution of magnetic moments gradually weakens the antiferromagnetic exchange interaction.Moreover,Ge doping reduces the critical field of ferromagnetic ordering,which may provide a possible way to implement the quantum anomalous Hall effect at lower magnetic field.Electrical transport measurements suggest that electrons are the dominant charge carriers,and the carrier density increases with the Ge doping ratio.Additionally,the Kondo effect is observed in the samples with x=0.45,0.60,and 0.75.Our results suggest that doping germanium is a viable way to tune the magnetic and electrical transport properties of MnBi2Te4,opening up the possibility of future applications in magnetic topological insulators.
查看更多>>摘要：The discovery of nickelates superconductor creates exciting opportunities to unconventional superconductivity.However,its synthesis is challenging and only a few groups worldwide can obtain samples with zero-resistance.This problem becomes the major barrier for this field.From plume dynamics perspective,we found the synthesis of superconducting nicke-lates is a complex process and the challenge is twofold,i.e.,how to stabilize an ideal infinite-layer structure Nd0.8Sr0.2NiO2,and then how to make Nd0.8Sr0.2NiO2 superconducting?The competition between perovskite Nd0.8Sr0.2NiO3 and Ruddlesden-Popper defect phase is crucial for obtain-ing infinite-layer structure.Due to inequivalent angular distributions of condensate during laser ablation,the laser energy density is critical to obtain phase-pure Nd0,8Sr0.2NiO3.However,for obtaining superconductivi-ty,both laser energy density and substrate temperature are very important.We also demonstrate the superconducting Nd0.8Sr0.2NiO2 epitaxial film is very stable in ambient conditions up to 512 days.Our results provide important insights for fabrication of superconducting infinite-layer nicke-lates towards future device applications.
查看更多>>摘要：We study how to use the surface states in a Bi2Se3 topological insulator ultra-thin film that are affected by finite size effects for the purpose of quantum computing.We demonstrate that:(ⅰ)surface states under the finite size effect can effectively form a two-level system where their energy levels lie in between the bulk energy gap and a logic qubit can be constructed,(ⅱ)the qubit can be initialized and manipulated using electric pulses of simple forms,(ⅲ)two-qubit entanglement is achieved through a√SWAP operation when the two qubits are in a parallel setup,and(ⅳ)alternatively,a Floquet state can be exploited to construct a qubit and two Floquet qubits can be entangled through a Controlled-NOT operation.The Floquet qubit offers robustness to background noise since there is always an oscillating electric field applied,and the single qubit operations are controlled by amplitude modulation of the oscillating field,which is convenient experimentally.
查看更多>>摘要：High-order nonlinear multiphoton absorption is usually inefficient,but can be enhanced by designing resonant excitations between occupied and unoccupied energy levels.We conducted angle-resolved multi-photon photoemission(mPPE)studies on the SnSe2(001)surfaces excited by ultra-short laser pulses.By tuning photon energy and light polarization,we demonstrate the presence of a resonant four-photon photoemission(4PPE)process involving the occupied valence band(VB),the unoccupied second conduction band(CB2)and the unoccupied image-potential state(IPs)of SnSe2.In this 4PPE process,VB electrons of SnSe2 are resonantly excited into CB2 by adsorbing two photons,followed by the adsorption of another photon to populate the n=1 IPs before being emitted out to the vacuum by adsorbing one more photon.This results in a double-resonant 4PPE process,which exhibits approximately a 40 times enhancement in photoe-mission yields compared to cases where one of the resonant pathways,CB2 →IPs,is inhibited by involving a virtual state instead of the IPs in the 4PPE.The double-resonant 4PPE process efficiently excite the bulk VB electrons outside the vacuum,like taking advantage of resonant"ladders"through two real empty electronic states of SnSe2.Our results highlight the important applications of mPPE in probing the band-structure,partic-ularly the unoccupied states,of recently emerging main group dichalco-genide semiconductors.Furthermore,the discovered resonant mPPE process contributes to the exploration of their promising optoelectronic applications.
查看更多>>摘要：We present a novel method to achieve the decoupling between the trans-mission and reflection waves of non-Hermitian doped epsilon-near-zero(ENZ)media by inserting a dielectric slit into the structure.Our method also allows for independent control over the amplitude and the phase of both the transmission and reflection waves through few dopants,enabling us to achieve various optical effects,such as perfect absorption,high-gain reflection without transmission,reflectionless high-gain transmission and reflectionless total transmission with different phases.By manipulating the permittivity of dopants with extremely low loss or gain,we can realize these effects in the same configuration.We also extend this principle to multi-port doped ENZ structures and design a highly reconfigurable and reflectionless signal distributor and generator that can split,amplify,decay and phase-shift the input signal in any desired way.Our method overcomes limitations of optical manipulation in doped ENZ caused by the interde-pendent nature of the transmission and reflection,and has potential appli-cations in novel photonic devices.
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