查看更多>>摘要：The ohmic contact interface between diamond and metal is essential for the application of diamond detectors.Sur-face modification can significantly affect the contact performance and eliminate the interface polarization effect.However,the radiation stability of a diamond detector is also sensitive to surface modification.In this work,the influence of sur-face modification technology on a diamond ohmic contact under high-energy radiation was investigated.Before radiation,the specific contact resistivities(ρc)between Ti/Pt/Au-hydrogen-terminated diamond(H-diamond)and Ti/Pt/Au-oxygen-terminated diamond(O-diamond)were 2.0 × 10-4 Ω·cm2 and 4.3 × 10-3 Ω·cm2,respectively.After 10 MeV electron radiation,the ρc of Ti/Pt/Au H-diamond and Ti/Pt/Au O-diamond were 5.3 × 10-3 Ω·cm2 and 9.1 × 10-3 Ω·cm2,respec-tively.The rates of change of ρc of H-diamond and O-diamond after radiation were 2550％and 112％,respectively.The electron radiation promotes bond reconstruction of the diamond surface,resulting in an increase in ρc.
查看更多>>摘要：The interplay between topology and magnetism is vital for realizing exotic quantum phenomena,significant examples including quantum anomalous Hall effect,axion insulators,and high-order topological states.These states host great poten-tial for future applications in high-speed and low-consumption electronic devices.Despite being extensively investigated,practical platforms are still scarce.In this work,with molecular beam epitaxy(MBE),we provide the first experimental report on high-quality Bi(l10)/CrTe2 magnetic heterostructure.By employing in-situ high-resolution scanning tunneling microscopy,we are able to examine the interaction between magnetism and topology.There is a potential edge state at an energy level above the Fermi level,but no edge states observed near the Fermi level The absence of high-order topolog-ical corner states near EF highlights the importance of lattice matching and interface engineering in designing high-order topological states.Our study provides key insights into the interplay between two-dimensional magnetic and topological materials and offers an important dimension for engineering magnetic topological states.
查看更多>>摘要：Materials with kagome lattices have attracted significant research attention due to their nontrivial features in energy bands.We theoretically investigate the evolution of electronic band structures of kagome lattices in response to uniaxial strain using both a tight-binding model and an antidot model based on a periodic muffin-tin potential.It is found that the Dirac points move with applied strain.Furthermore,the flat band of unstrained kagome lattices is found to develop into a highly anisotropic shape under a stretching strain along y direction,forming a partially flat band with a region dispersionless along ky direction while dispersive along kx direction.Our results shed light on the possibility of engineering the electronic band structures of kagome materials by mechanical strain.
查看更多>>摘要：We investigate the electronic structure of NbGeSb with non-symmorphic symmetry.We employ angle-resolved pho-toemission spectroscopy(ARPES)to observe and identify the bulk and surface states over the Brillouin zone.By utilizing high-energy photons,we identify the bulk Fermi surface and bulk nodal line along the direction X-R,while the Fermi surface of the surface state is observed by using low-energy photons.We observe the splitting of surface bands away from the high-symmetry point(X).The density functional theory calculations on bulk and 1 to 5-layer slab models,as well as spin textures of NbGeSb,verify that the band splitting could be attributed to the Rashba-like spin-orbit coupling caused by space-inversion-symmetry breaking at the surface.These splitted surface bands cross with each other,form-ing two-dimensional Weyl-like crossings that are protected by mirror symmetry.Our findings provide insights into the two-dimensional topological and symmetry-protected band inversion of surface states.
查看更多>>摘要：For the past few years,germanium-based semiconductor spintronics has attracted considerable interest due to its po-tential for integration into mainstream semiconductor technology.The main challenges in the development of modern semi-conductor spintronics are the generation,detection,and manipulation of spin currents.Here,the transport characteristics of a spin current generated by spin pumping through a GeBi semiconductor barrier in Y3Fe5O12/GeBi/Pt heterostructures were investigated systematically.The effective spin-mixing conductance and inverse spin Hall voltage to quantitatively describe the spin transport characteristics were extracted.The spin-injection efficiency in the Y3Fe5O12/GeBi/Pt heterostructures is comparable to that of the Y3Fe5O12/Pt bilayer,and the inverse spin Hall voltage exponential decays with the increase in the barrier thickness.Furthermore,the band gap of the GeBi layer was tuned by changing the Bi content.The spin-injection efficiency at the YIG/semiconductor interface and the spin transportation within the semiconductor barrier are related to the band gap of the GeBi layer.Our results may be used as guidelines for the fabrication of efficient spin transmission structures and may lead to further studies on the impacts of different kinds of barrier materials.
查看更多>>摘要：We investigate the chiral edge states-induced Josephson current-phase relation in a graphene-based Josephson junc-tion modulated by the off-resonant circularly polarized light and the staggered sublattice potential.By solving the Bogoliubov-de Gennes equation,a φ0 Josephson junction is induced in the coaction of the off-resonant circularly po-larized light and the staggered sublattice potential,which arises from the fact that the center of-mass wave vector of Cooper pair becomes finite and the opposite center of-mass wave vector to compensate is lacking in the nonsuperconducting re-gion.Interestingly,when the direction of polarization of light is changed,-φ0 to φ0 transition generates,which generalizes the concept of traditional 0-π transition.Our findings provide a purely optical way to manipulate a phase-controllable Josephson device and guidelines for future experiments to confirm the presence of graphene-based φ0 Josephson junction.
查看更多>>摘要：Disordered superconducting materials like NbTiN possess a high kinetic inductance fraction and an adjustable critical temperature,making them a good choice for low-temperature detectors.Their energy gap(4),critical temperature(Tc),and quasiparticle density of states(QDOS)distribution,however,deviate from the classical BCS theory due to the disorder effects.The Usadel equation,which takes account of elastic scattering,non-elastic scattering,and electro-phonon coupling,can be applied to explain and describe these deviations.This paper presents numerical simulations of the disorder effects based on the Usadel equation to investigate their effects on the Δ,Tc,QDOS distribution,and complex conductivity of the NbTiN film.Furthermore,NbTiN superconducting resonators with coplanar waveguide(CPW)structures are fabricated and characterized at different temperatures to validate our numerical simulations.The pair-breaking parameter α and the critical temperature in the pure state TcP of our NbTiN film are determined from the experimental results and numerical simulations.This study has significant implications for the development of low-temperature detectors made of disordered superconducting materials.
查看更多>>摘要：Dzyaloshinskii-Moriya interaction(DMI)is under extensive investigation considering its crucial status in chiral mag-netic orders,such as Néel-type domain wall(DW)and skyrmions.It has been reported that the interfacial DMI originating from Rashba spin-orbit coupling(SOC)can be linearly tuned with strong external electric fields.In this work,we experi-mentally demonstrate that the strength of DMI exhibits rapid fluctuations,ranging from 10％to 30％of its original value,as a function of applied electric fields in Pt/Co/MgO heterostructures within the small field regime(＜10-2 V/nm).Brillouin light scattering(BLS)experiments have been performed to measure DMI,and first-principles calculations show agreement with this observation,which can be explained by the variation in orbital hybridization at the Co/MgO interface in response to the weak electric fields.Our results on voltage control of DMI(VCDMI)suggest that research related to the voltage control of magnetic anisotropy for spin-orbit torque or the motion control of skyrmions might also have to consider the role of the external electric field on DMI as small voltages are generally used for the magnetoresistance detection.
查看更多>>摘要：Two-dimensional(2D)magnet/superconductor heterostructures can promote the design of artificial materials for ex-ploring 2D physics and device applications by exotic proximity effects.However,plagued by the low Curie temperature and instability in air,it is hard to realize practical applications for the reported layered magnetic materials at present.In this pa-per,we developed a space-confined chemical vapor deposition method to synthesize ultrathin air-stable ε-Fe2O3 nanosheets with Curie temperature above 350 K.The ε-Fe2O3/NbSe2 heterojunction was constructed to study the magnetic proximity effect on the superconductivity of the NbSe2 multilayer.The electrical transport results show that the subtle proximity effect can modulate the interfacial spin-orbit interaction while undegrading the superconducting critical parameters.Our work paves the way to construct 2D heterojunctions with ultrathin nonlayered materials and layered van der Waals(vdW)materials for exploring new physical phenomena.
查看更多>>摘要：Recently,significant experimental advancements in achieving topological phases have been reported in van der Waals(vdW)heterostructures involving graphene.Here,using first-principles calculations,we investigate graphene/CoBr2(Gr/CoBr2)heterostructures and find that an enhancement of in-plane magnetic anisotropy(IMA)energy in monolayer CoBr2 can be accomplished by reducing the interlayer distance of the vdW heterostructures.In addition,we clarify that the enhancement of IMA energy primarily results from two factors:one is the weakness of the Co-dvv and Co-dx2-y2 orbital hybridization and the other is the augmentation of the Co-dyz and Co-dz2 orbital hybridization.Meanwhile,calculation results suggest that the Kosterlitz-Thouless phase transition temperature(TKT)of a 2D XY magnet Gr/CoBr2(23.8 K)is higher than that of a 2D XY monolayer CoBr2(1.35 K).By decreasing the interlayer distances,the proximity effect is more pronounced and band splitting appears.Moreover,by taking into account spin-orbit coupling,a band gap of approx-imately 14.3 meV and the quantum anomalous Hall effect(QAHE)are attained by decreasing the interlayer distance by 1.0 Å.Inspired by the above conclusions,we design a topological field transistor device model.Our results support that the vdW interlayer distance can be used to modulate the IMA energy and QAHE of materials,providing a pathway for the development of new low-power spintronic devices.
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