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Chern and Z2 topological insulating phases in perovskite-derived 4d and 5d oxide buckled honeycomb lattices
摘要： Based on density functional theory calculations including a coulomb repulsion parameter U, we explore the topological properties of (LaXo3)2/(LaAlo3)4 (111) with X = 4d and 5d cations. the metastable ferromagnetic phases of Latco3 and Lapto3 with preserved P321 symmetry emerge as Chern insulators (CI) with C = 2 and 1 and band gaps of 41 and 38 meV at the lateral lattice constant of LaAlo3, respectively. Berry curvatures, spin textures as well as edge states provide additional insight into the nature of the ci states. While for X = Tc the CI phase is further stabilized under tensile strain, for X = Pd and Pt a site disproportionation takes place when increasing the lateral lattice constant from aLAo to aLno. the ci phase of X = Pt shows a strong dependence on the Hubbard U parameter with sign reversal for higher values associated with the change of band gap opening mechanism. Parallels to the previously studied (X2o3)1/(Al2o3)5 (0001) honeycomb corundum layers are discussed. Additionally, non-magnetic systems with X = Mo and W are identified as potential candidates for Z2 topological insulators at aLAo with band gaps of 26 and 60 meV, respectively. The computed edge states and Z2 invariants underpin the non-trivial topological properties.
关键词： density functional theory,perovskite-derived oxides,Chern insulators,Z2 topological insulators,honeycomb lattices
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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Routine Microscopy in Quantum Dot Industry
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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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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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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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
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Surfaces of axion insulators
摘要： Axion insulators are magnetic topological insulators in which the nontrivial Z2 index is protected by inversion symmetry instead of time-reversal symmetry. The naturally gapped surfaces of axion insulators give rise to a half-quantized surface anomalous Hall conductivity (AHC), but the sign of the surface AHC cannot be determined from topological arguments. In this paper, we consider topological phenomena at the surface of an axion insulator. To be explicit, we construct a minimal tight-binding model on the pyrochlore lattice and investigate the all-in-all-out (AIAO) and ferromagnetic (FM) spin configurations. We also implement a recently proposed approach for calculating the surface AHC directly, which allows us to explore how the interplay between surface termination and magnetic ordering determines the sign of the half-quantized surface AHC. In the case of AIAO ordering, we show that it is possible to construct a topological state with no protected metallic states on boundaries of any dimension (surfaces, hinges, or corners), although chiral hinge modes do occur for many surface configurations. In the FM case, rotation of the magnetization by an external field offers promising means of control of chiral hinge modes, which can also appear on surface steps or where bulk domain walls emerge at the surface.
关键词： pyrochlore lattice,all-in-all-out,topological insulators,axion insulators,ferromagnetic,anomalous Hall conductivity
更新于2025-09-04 15:30:14