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topological insulator nanostructures： Materials synthesis, Raman spectroscopy, and transport properties

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Frontiers of physics 2012年第2期7卷 208-217页

作者：李辉彭海琳党文辉余力立刘忠范 1. Center for Nanochemistry Beijing National Laboratory for Molecular Sciences (BNLMS) State Key Laboratory for Structural Chemistry of Unstable and Stable Species College of Chemistry and Molecular Engineering Peking University Beijing 100871 China

Nanostructured topological insulator materials such as ultrathin films, nanoplates, nanowires, and nanoribbons are attracting much attention for fundamental research as well as potential applications in low-energy dissipation electronics, spintronics, thermoelectrics, magnetoelectrics, and quantum computing due to their extremely large surface-to-volume ratios and exotic metallic edge/surface states. Layered Bi2Se3 and Bi2Te3 serve as reference topological insulator materials with a large nontrivial bulk gap up to 0.3 eV （equivalent to 3600 K） and simple single-Dirac-cone surface states. In this mini-review, we present an overview of recent advances in nanostructured topological in- sulator Bi2Se3 and Bi3Te3 from the viewpoints of controlled synthesis and physical properties. We summarize our recent achievements in the vapor-phase synthesis and structural characteriza- tion of nanostructured topological insulator Bi2Se3 and Bi2Te3, such as nanoribbons and ultrathin nanoplates. We also demonstrate the evolution of Raman spectra with the number of few-layer topo- logical insulators, as well as the transport measurements that have succeeded in accessing the surface conductance and surface state manipulations in the device of topological insulator nanostructures.

关键词： topological insulator nanostructure synthesis Raman transport surface state manip-ulation

Higher-order topological Anderson insulator on the Sierpiński lattice

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Chinese Physics B 2024年第1期33卷 218-222页

作者：陈焕刘峥嵘陈锐周斌 Department of Physics Hubei UniversityWuhan 430062China Key Laboratory of Intelligent Sensing System and Security of Ministry of Education Hubei UniversityWuhan 430062China

Disorder effects on topological materials in integer dimensions have been extensively explored in recent years. However, its influence on topological systems in fractional dimensions remains unclear. Here, we investigate the disorder effects on a fractal system constructed on the Sierpiński lattice in fractional dimensions. The system supports the second-order topological insulator phase characterized by a quantized quadrupole moment and the normal insulator phase. We find that the second-order topological insulator phase on the Sierpiński lattice is robust against weak disorder but suppressed by strong disorder. Most interestingly, we find that disorder can transform the normal insulator phase to the second-order topological insulator phase with an emergent quantized quadrupole moment. Finally, the disorder-induced phase is further confirmed by calculating the energy spectrum and the corresponding probability distributions.

关键词： fractal system topological insulator

Electronic states and spin-filter effect in three-dimensional topological insulator Bi_2Se_3 nanoribbons

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Chinese Physics B 2018年第1期27卷 526-534页

作者：刘根华肖平国徐飘荣周慧英周光辉 College of Computer and Information Engineering Central South University of Forestry and Technology Department of Physics and Key Laboratory for Low-Dimensional Quantum Structures and Manipulation (Ministry of Education) Hunan Normal University

We study the electronic band structure, density distribution, and transport of a Bi2Se3 nanoribbon, We find that the density distribution of the surface states is dependent on not only the shape and size of the transverse cross section of the nanoribbon, but also the energy of the electron. We demonstrate that a transverse electric field can eliminate the coupling between surface states on the walls of the nanoribbon, remove the gap of the surface states, and restore the quantum spin Hall effects. In addition, we study the spin-dependent transport property of the surface states transmitting from top and bottom surfaces （x-y plane） to the side surfaces （z-x plane） of a Bi2Se3 nanoribbon. We find that transverse electric fields can open two surface channels for spin-up and -down Dirac electrons, and then switch off one channel for the spin-up Dirac electron. Our results may provide a simple way for the design of a spin filter based on topological insulator nanostructures.

关键词： topological insulator Bi2Se3 nanoribbon density distribution electronic transport

Electron states scattering off line edges on the surface of topological insulator

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Chinese Physics B 2014年第10期23卷 477-482页

作者：邵怀华刘一曼周小英周光辉 Department of Physics and Key Laboratory for Low-Dimensional Structures and Quantum Manipulation (Ministry of Education) Hunan Normal University

We study the local density of states （LDOS） for electrons scattering off the line edge of an atomic step defect on the surface of a three-dimensional （3D） topological insulator （TI） and the line edge of a finite 3D TI, where the front surface and side surface meet with different Fermi velocities, respectively. By using a S-function potential to model the edges, we find that the bound states existed along the step line edge significantly contribute to the LDOS near the edge, but do not modify the exponential behavior away from it. In addition, the power-law decaying behavior for LDOS oscillation away from the step is understood from the spin rotation for surface states scattering off the step defect with magnitude depending on the strength of the potential. Furthermore, the electron refraction and total reflection analogous to optics occurred at the line edge where two surfaces meet with different Fermi velocities, which leads to the LDOS decaying behavior in the greater Fermi velocity side similar to that for a step line edge. However, in the smaller velocity side the LDOS shows a different decaying behavior as x-1/2, and the wavevector of LDOS oscillation is no longer equal to the diameter of the constant energy contour of surface band, but is sensitively dependent on the ratio of the two Fermi velocities. These effects may be verified by STM measurement with high precision.

关键词： topological insulator line defects local density of states

Charge transport and shot noise on the surface of a topological insulator with a magnetic modulation

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Chinese Physics B 2012年第4期21卷 461-466页

作者：袁建辉成泽张建军曾奇军张俊佩 School of Physics Huazhong University of Science and TechnologyWuhan 430074China

In this paper, we investigate the transport features and the Fano factor of Dirac electrons on the surface of a three-dimensional topological insulator with a magnetic modulation. We consider a hard wall bounding condition on the edge of the topological insulator, which implies that a surface state of the topological insulator is insulating. We find that a valley of conductivity at the Dirac point is associated with a Fano factor peak, and more interestingly, this topological metal changes from insulating to metallic by controlling the effective exchange field.

关键词： topological insulator electronic transport ferrimagnetic

Femtosecond Tm-Ho co-doped fiber laser using a bulk-structured Bi2Se3 topological insulator

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Chinese Physics B 2018年第9期27卷 137-143页

作者： Jinho Lee Ju Han Lee School of Electrical and Computer Engineering University of SeoulSeoul 02504Republic of Kore

We experimentally demonstrate a femtosecond mode-locked thulium-holmium（Tm-Ho） co-doped fiber laser incorporating a saturable absorber（SA） based on a bulk-structured bismuth selenide（Bi2Se3） topological insulator（TI）. The SA was prepared by depositing a mechanically exfoliated Bi2Se3 TI layer onto a side-polished optical fiber platform. Unlike high-quality nano-structured Bi2Se3 TI-based SA, bulk-structured Bi2Se3 with non-negligible oxidation was used as a saturable absorption material for this experimental demonstration due to its easy fabrication process. The saturation power and modulation depth of the prepared SA were measured to be -28.6 W and -13.4%, respectively. By incorporating the prepared SA into a Tm-Ho co-doped fiber ring cavity, stable soliton pulses with a temporal width of - 853 fs could be generated at 1912.12 nm. The 3-dB bandwidth of the mode-locked pulse was measured to be -4.87 nm. This experimental demonstration reaffirms that Bi2Se3 is a superb base material for mid-infrared passive mode-locking even under oxidation.

关键词： topological insulator mode-locked lasers femtosecond pulse fiber lasers

Molecular-beam epitaxy of topological insulator Bi_2Se_3(111) and (221) thin films

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Chinese Physics B 2013年第6期22卷 91-98页

作者：谢茂海郭欣徐忠杰何永健 Physics Department The University of Hong Kong

This paper presents an overview of the growth of Bi2Se3, a prototypical three-dimensional topological insulator, by molecular-beam epitaxy on various substrates. Comparison is made between the growth of Bi2 Se3 （111） on van der Waals （vdW） and non-vdW substrates, with attention paid to twin suppression and strain. Growth along the [221] direction of Bi2Se3 on InP （001） and GaAs （001） substrates is also discussed.

关键词： topological insulator molecular-beam epitaxy Bi2Se3 twin domain strain

Sb2Te3 topological insulator for 52 nm wideband tunable Yb-doped passively Q-switched fiber laser

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Frontiers of Information Technology & Electronic Engineering 2021年第3期22卷 287-295页

作者： Tao WANG Qiang YU Kun GUO Xinyao SHI Xuefen KAN Yijun XU Jian WU Kai ZHANG Pu ZHOU College of Advanced Interdisciplinary Studies National University of Defense TechnologyChangsha 410073China i-Lab Suzhou Institute of Nano-Tech and Nano-BionicsChinese Academy of SciencesSuzhou 215123China Jiangsu Key Laboratory of Power Transmission and Distribution Equipment Technology Hohai UniversityChangzhou 213022China Key Laboratory of Nano-Devices and Applications Suzhou Institute of Nano-Tech and Nano-BionicsChinese Academy of SciencesSuzhou 215123China Vacuum Interconnected Nanotech Workstation Suzhou Institute of Nano-Tech and Nano-BionicsChinese Academy of SciencesSuzhou 215123China

topological insulator Sb2Te3 has the advantage of broadband saturable absorption from the visible to the infrared ***,the two-dimensional material Sb2Te3 saturable absorber(SA)of the topological insulator family was first applied experimentally in a wideband tunable passively Q-switched Yb-doped fiber ***-quality Sb2Te3 crystals were synthesized by the flux zone *** Sb2Te3 SA with fewer layers was further prepared via a modified mechanical exfoliation ***,stable wavelength-tunable passive Q-switching pulse operation was obtained in a Yb-doped fiber ring cavity based on the Sb2Te3 SA,where the central wavelength can be continuously tuned from 1040.89 to 1092.85 *** suggest that Sb2Te3 has wideband saturable absorption properties,and that the tunable pulse laser can provide a convenient and simple source for practical applications.

关键词： topological insulator Sb2Te3 Fiber laser Passive Q-switching laser Wavelength-tunable laser

Growth and transport properties of topological insulator Bi2Se3 thin film on a ferromagnetic insulating substrate

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Chinese Physics B 2018年第7期27卷 431-437页

作者： Shanna Zhu Gang Shi Peng Zhao Dechao Meng Genhao Liang Xiaofang Zhai Yalin Lu Yongqing Li Lan Chen Kehui Wu Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China Hefei National Laboratory for Physical Sciences at the Microscale University of Science and Technology of ChinaHefei 230026China Microsystem and Terahertz Research Center ＆ Institute of Electronic Engineering CAER Mianyang 621900China Synergy Innovation Center of Quantum Information and Quantum Physics University of Science and Technology of ChinaHefei 230026China National Synchrotron Radiation Laboratory University of Science and Technology of ChinaHefei 230026China Collaborative Innovation Center of Quantum Matter.Beijing 100871 China

Exchange coupling between topological insulator and ferromagnetic insulator through proximity effect is strongly attractive for both fundamental physics and technological applications. Here we report a comprehensive investigation on the growth behaviors of prototype topological insulator Bi2Se3 thin film on a single-crystalline LaCoO3 thin film on SrTiO3 substrate, which is a strain-induced ferromagnetic insulator. Different from the growth on other substrates, the Bi2Se3 films with highest quality on LaCoO3 favor a relatively low substrate temperature during growth. As a result, an inverse dependence of carrier mobility with the substrate temperature is found. Moreover, the magnetoresistance and coherence length of weak antilocalization also have a similar inverse dependence with the substrate temperature, as revealed by the magnetotransport measurements. Our experiments elucidate the special behaviors in Bi2Se3/LaCoO3 heterostructures, which provide a good platform for exploring related novel quantum phenomena, and are inspiring for device applications.

关键词： topological insulator ferromagnetic insulator molecular beam epitaxy magnetotransport proper-ties