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The Quest for Zero Loss: Unconventional Materials for Plasmonics
摘要： There has been an ongoing quest to optimize the materials used to build plasmonic devices: first the elements were investigated, then alloys and intermetallic compounds, later semiconductors were considered, and, most recently, there has been interest in using more exotic materials such as topological insulators and conducting oxides. The quality of the plasmon resonances in these materials is closely correlated with their structure and properties. In general gold and silver are the most commonly specified materials for these applications but they do have weaknesses. Here, it is shown how, in specific circumstances, the selection of certain other materials might be more useful. Candidate alternatives include TixN, VO2, Al, Cu, Al-doped ZnO, and Cu–Al alloys. The relative merits of these choices and the many pitfalls and subtle problems that arise are discussed, and a frank perspective on the field is provided.
关键词： plasmonics,conducting oxides,topological insulators,intermetallic compounds,figure-of-merit,material selection
更新于2025-09-11 14:15:04
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Epitaxial Growth of Topological Insulators on Semiconductors (Bi <sub/>2</sub> Se <sub/>3</sub> /Te@Se) toward High-Performance Photodetectors
摘要： Heterojunctions, composed of different materials, are widely explored in optoelectronic devices thanks to their unique advantages, such as high carrier mobility and excellent photoelectronic characteristics. In this work, Bi2Se3/Te@Se heterojunctions (Bi2Se3/Te@Se) are synthesized through the epitaxial growth of Bi2Se3 nanosheets (Bi2Se3 NTs) on tellurium@selenium nanotubes (Te@Se NTs) by using a low-cost and facile solvothermal process. Bi2Se3/Te@Se are further applied in high-performance photoelectrochemical (PEC)-type photodetection due to the advantages of broadband optical response and fast carrier relaxation time. The PEC results demonstrate that the as-prepared photodetectors have pronounced photoresponse behavior from the ultraviolet to visible band with self-driven ability and excellent long-term stability. It is anticipated that this work provides a new strategy for epitaxial growth of topological insulators on semiconductors for designing new heterojunctions toward high-performance optoelectronic devices.
关键词： photodetectors,self-driven,topological insulators,epitaxial growth,heterojunctions
更新于2025-09-11 14:15:04
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Proximity-induced supercurrent through topological insulator based nanowires for quantum computation studies
摘要： Proximity-induced superconducting energy gap in the surface states of topological insulators has been predicted to host the much wanted Majorana fermions for fault-tolerant quantum computation. Recent theoretically proposed architectures for topological quantum computation via Majoranas are based on large networks of Kitaev’s one-dimensional quantum wires, which pose a huge experimental challenge in terms of scalability of the current single nanowire based devices. Here, we address this problem by realizing robust superconductivity in junctions of fabricated topological insulator (Bi2Se3) nanowires proximity-coupled to conventional s-wave superconducting (W) electrodes. Milling technique possesses great potential in fabrication of any desired shapes and structures at nanoscale level, and therefore can be effectively utilized to scale-up the existing single nanowire based design into nanowire based network architectures. We demonstrate the dominant role of ballistic topological surface states in propagating the long-range proximity induced superconducting order with high IcRN product in long Bi2Se3 junctions. Large upper critical magnetic fields exceeding the Chandrasekhar-Clogston limit suggests the existence of robust superconducting order with spin-triplet cooper pairing. An unconventional inverse dependence of IcRN product on the width of the nanowire junction was also observed.
关键词： Topological insulators,Quantum computation,Nanowires,Majorana fermions,Ballistic topological surface states,Proximity-induced superconductivity,Spin-triplet cooper pairing
更新于2025-09-11 14:15:04
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Half-Metallic Ferromagnetism Character in Cr-Doped CaS Diluted Magnetic Insulator and Semiconductor: an Ab Initio Study
摘要： The overall aim of this study is to investigate theoretically the structural, electronic, and magnetic properties of calcium sulfide (CaS) doped with chromium (Cr) impurity, in order to conduct a new search dilute magnetic semiconductors (DMS) suitable for different applications in electronics and spintronics. For measuring, the physical property of this compound is implemented using the first principles approach employed in WIEN2K code. The structural characteristics are optimized using the Generalized Gradient Approximation established by Perdew-Burk-Ernzerhof (PBE-GGA). We calculate and minimize the total energy of the three ternary compounds (Ca0.75Cr0.25S, Ca0.50Cr0.50S, and Ca0.25Cr0.75S) in the paramagnetic (PM), ferromagnetic (FM), and antiferromagnetic (AFM) phase. We find all compounds stable in (FM) structure, whereas the modified Becke and Johnson local density approximation (mBJ-LDA) functional has been employed to evaluate the electronic and magnetic properties. Based on our findings, indicate that this system revealed a half-metallic ferromagnetic behavior with half-metallic gap (HM) and 100% spin-polarized at the fermi level for all chromium (Cr) concentrations. This advantageous set of properties is due to the half-metallic behavior, where the majority spin and minority spin exhibit metallic and semiconducting behaviors respectively. The chromium atom is the most important source of the total magnetic moment in these compounds (4 μβ) by comparison with magnetic moments produced by Ca and S atoms, which have minor contribution. Finally, our prediction results require an experimental confirmation in the future.
关键词： Diluted magnetic insulators (DMI),Spintronics,CaS,HM ferromagnetism,Density functional theory (DFT)
更新于2025-09-10 09:29:36
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Enhancement in surface mobility and quantum transport of Bi2?xSbxTe3?ySey topological insulator by controlling the crystal growth conditions
摘要： Despite numerous studies on three-dimensional topological insulators (3D TIs), the controlled growth of high quality (bulk-insulating and high mobility) TIs remains a challenging subject. This study investigates the role of growth methods on the synthesis of single crystal stoichiometric BiSbTeSe2 (BSTS). Three types of BSTS samples are prepared using three different methods, namely melting growth (MG), Bridgman growth (BG) and two-step melting-Bridgman growth (MBG). Our results show that the crystal quality of the BSTS depend strongly on the growth method. Crystal structure and composition analyses suggest a better homogeneity and highly-ordered crystal structure in BSTS grown by MBG method. This correlates well to sample electrical transport properties, where a substantial improvement in surface mobility is observed in MBG BSTS devices. The enhancement in crystal quality and mobility allow the observation of well-developed quantum Hall effect at low magnetic field.
关键词： two-step melting-Bridgman growth,three-dimensional topological insulators,surface mobility,quantum Hall effect,Bridgman growth,melting growth,BiSbTeSe2
更新于2025-09-10 09:29:36
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Investigation of the performance of strain-engineered silicon nanowire field effect transistors (?-Si-NWFET) on IOS substrates
摘要： In the current work, a design space for developing the performance enhanced strain-engineered Si nanowire field-effect-transistors has been provided. The fraction of insertion of the nanowire channel into the Insulator-on-Silicon substrate with judicious selection of high-k gate insulators is used as the key design parameter. The combined effect of fractional insertion and gate insulators results in inducing stress into the nanowire channel and, depending on their selection, it changes from tensile to compressive. Such induced-stress alters the existing inherent phononic-stress, leading to the modification of the carrier transport in the device channel. The carrier transport behavior in such partially embedded nanowire FETs has been modeled by incorporating the relevant stress-related effects into the indigenously developed self-consistent quantum-electrostatic framework. These equations are solved by employing the non-equilibrium Green’s function formalism. The study shows the phonon scattering under tensile strain to occur at the expense of electron energy; however, the electrons can also gain energy during such scattering in compressive stress. Thus, the device current has been observed to increase with tensile stress and it achieves relatively smaller values when the inherent tensile phononic stress is balanced by the induced compressive stress. However, the current is finally observed to increase once the compressive stress overcomes the inherent tensile phononic stress. In general, the present devices exhibit promising Ion/Ioff ratio for all of the fractional insertions and gate dielectrics with a maximum Ioff of <10 nA/μm, threshold voltage of sub-0.3 V, gm of ～104 μS/μm, sub-threshold swing of ～100 mV/dec, and drain-induced-barrier-lowering of ～100 mV/V.
关键词： IOS substrates,high-k gate insulators,strain-engineered,silicon nanowire,non-equilibrium Green’s function,quantum-electrostatic framework,field-effect transistors
更新于2025-09-10 09:29:36
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Electrically tunable valleytronics in quantum anomalous Hall insulating transition metal trihalides
摘要： We propose a different scheme for achieving valley splitting using an electric ?eld in the materials with inversion symmetry but without time-reversal symmetry, and apply this scheme to two-dimensional transition metal trihalides VX3 (X = Cl, Br). Based on ab initio calculations and the tight-binding model, we ?nd few layer VX3 can be readily tuned from intrinsic quantum anomalous Hall insulators to quantum valley Hall insulators by external electric ?elds. Especially, the electric-?eld-induced valley splitting of the bilayer VX3 is extremely large, about two orders of magnitude higher than that induced by a magnetic ?eld in the state-of-the-art valleytronic materials (e.g., MoS2 and WSe2). We further reveal rich topological phases of few layer VX3 and valley-polarized states at the phase boundary. These ?ndings may motivate further topology and valleytronics related researches in low-dimensional transition metal compounds.
关键词： quantum valley Hall insulators,valleytronics,quantum anomalous Hall insulators,transition metal trihalides,electric ?eld,topological phases
更新于2025-09-09 09:28:46
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Phase-coherent transport in selectively grown topological insulator nanodots
摘要： Oxidized Si(111) substrates were pre-structured by electron beam lithography and used as a substrate for the selective growth of three-dimensional topological insulators (TI) by molecular beam epitaxy. The patterned holes were filled up by the TI, i.e. Sb2Te3 and Bi2Te3, to form nanodots. Scanning electron microscopy and focused ion beam cross-sectioning was utilized to determine the morphology and depth profile of the nanodots. The magnetotransport measurements revealed universal conductance fluctuations originating from electron interference in phase-coherent loops. We find that these loops are oriented preferentially within the quintuple layers of the TI with only a small perpendicular contribution. Furthermore, we found clear indications of an conductivity anisotropy between different crystal orientations.
关键词： phase-coherent transport,magnetotransport,selective area growth,topological insulators,molecular beam epitaxy
更新于2025-09-09 09:28:46
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SU(3) topological insulators in the honeycomb lattice
摘要： We investigate realizations of topological insulators with spin-1 bosons loaded in a honeycomb optical lattice and subjected to a SU(3) spin-orbit coupling—a situation which can be realized experimentally using cold atomic gases. In this paper, we focus on the topological properties of the single-particle band structure, namely, Chern numbers (lattice with periodic boundary conditions) and edge states (lattice with strip geometry) and their connection to time-reversal symmetry and the sublattice symmetry. While SU(2) spin-orbit couplings always lead to time-reversal symmetric tight-binding models, and thereby to topologically trivial band structures, suitable SU(3) spin-orbit couplings can break time-reversal symmetry and lead to topologically nontrivial bulk band structures and to edge states in the strip geometry. In addition, we show that one can trigger a series of topological transitions (i.e., integer changes of the Chern numbers) that are speci?c to the geometry of the honeycomb lattice by varying a single parameter in the Hamiltonian.
关键词： sublattice symmetry,SU(3) spin-orbit coupling,honeycomb optical lattice,spin-1 bosons,time-reversal symmetry,edge states,topological insulators,Chern numbers
更新于2025-09-09 09:28:46
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Optical properties of helical edge channels in zinc-blende-type topological insulators: Selection rules, circular and linear dichroism, circular and linear photocurrents
摘要： We develop a theory of electron-photon interaction for helical edge channels in two-dimensional topological insulators based on zinc-blende-type quantum wells. It is shown that the lack of space inversion symmetry in such structures enables the electro-dipole optical transitions between the spin branches of the topological edge states. Further, we demonstrate the linear and circular dichroism associated with the edge states and the generation of edge photocurrents controlled by radiation polarization.
关键词： circular dichroism,edge photocurrents,topological insulators,electron-photon interaction,linear dichroism,helical edge channels
更新于2025-09-09 09:28:46