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1.
Matthew Brahlek 《Advanced materials (Deerfield Beach, Fla.)》2020,32(50):2005698
The unusual electronic states found in topological materials can enable a new generation of devices and technologies, yet a long-standing challenge has been finding materials without deleterious parallel bulk conduction. This can arise either from defects or thermally activated carriers. Here, the criteria that materials need to meet to realize transport properties dominated by the topological states, a necessity for a topological device, are clarified. This is demonstrated for 3D topological insulators, 3D Dirac materials, and 1D quantum anomalous Hall insulators, though this can be applied to similar systems. The key parameters are electronic bandgap, dielectric constant, and carrier effective mass, which dictate under what circumstances (defect density, temperature, etc.) the unwanted bulk state will conduct in parallel to the topological states. As these are fundamentally determined by the basic atomic properties, simple chemical arguments can be used to navigate the phase space to ultimately find improved materials. This will enable rapid identification of new systems with improved properties, which is crucial to designing new material systems and push a new generation of topological technologies. 相似文献
2.
Chun‐Wei Chen Natalia Lera Rajesh Chaunsali Daniel Torrent Jose Vicente Alvarez Jinkyu Yang Pablo San‐Jose Johan Christensen 《Advanced materials (Deerfield Beach, Fla.)》2019,31(51)
The discovery of topologically nontrivial electronic systems has opened a new age in condensed matter research. From topological insulators to topological superconductors and Weyl semimetals, it is now understood that some of the most remarkable and robust phases in electronic systems (e.g., quantum Hall or anomalous quantum Hall) are the result of topological protection. These powerful ideas have recently begun to be explored also in bosonic systems. Topologically protected acoustic, mechanical, and optical edge states have been demonstrated in a number of systems that recreate the requisite topological conditions. Such states that propagate without backscattering could find important applications in communications and energy technologies. Here, a topologically bound mechanical state, a different class of nonpropagating protected state that cannot be destroyed by local perturbations, is demonstrated. It is in particular a mechanical analogue of the well‐known Majorana bound states (MBSs) of electronic topological superconductor systems. The topological binding is implemented by creating a Kekulé distortion vortex on a 2D mechanical honeycomb superlattice that can be mapped to a magnetic flux vortex in a topological superconductor. 相似文献
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N. V. Tarakina S. Schreyeck M. Luysberg S. Grauer C. Schumacher G. Karczewski K. Brunner C. Gould H. Buhmann R. E. Dunin‐Borkowski L. W. Molenkamp 《Advanced Materials Interfaces》2014,1(5)
The microstructure of Bi2Se3 topological‐insulator thin films grown by molecular beam epitaxy on InP(111)A and InP(111)B substrates that have different surface roughnesses has been studied in detail using X‐ray diffraction, X‐ray reflectivity, atomic force microscopy and probe‐corrected scanning transmission electron microscopy. The use of a rough Fe‐doped InP(111)B substrate results in complete suppression of twin formation in the Bi2Se3 thin films and a perfect interface between the films and their substrates. The only type of structural defect that persists in the twin‐free films is an antiphase domain boundary, which is associated with variations in substrate height. We also show that the substrate surface termination influences which family of twin domains dominates. 相似文献
5.
Disorder, ubiquitously present in realistic structures, is generally thought to disturb the performance of analog wave devices, as it often causes strong multiple scattering effects that largely arrest wave transportation. Contrary to this general view, here, it is shown that, in some wave systems with nontrivial topological character, strong randomness can be highly beneficial, acting as a powerful stimulator to enable desired analog filtering operations. This is achieved in a topological Anderson sonic crystal that, in the regime of dominating randomness, provides a well-defined filtering response characterized by a Lorentzian spectral line-shape. The theoretical and experimental results, serving as the first realization of topological Anderson insulator phase in acoustics, suggest the striking possibility of achieving specific, nonrandom analog filtering operations by adding randomness to clean structures. 相似文献
6.
Lei Pan Alexander Grutter Peng Zhang Xiaoyu Che Tomohiro Nozaki Alex Stern Mike Street Bing Zhang Brian Casas Qing Lin He Eun Sang Choi Steven M. Disseler Dustin A. Gilbert Gen Yin Qiming Shao Peng Deng Yingying Wu Xiaoyang Liu Xufeng Kou Sahashi Masashi Xiaodong Han Christian Binek Scott Chambers Jing Xia Kang L. Wang 《Advanced materials (Deerfield Beach, Fla.)》2020,32(34):2001460
Integration of a quantum anomalous Hall insulator with a magnetically ordered material provides an additional degree of freedom through which the resulting exotic quantum states can be controlled. Here, an experimental observation is reported of the quantum anomalous Hall effect in a magnetically-doped topological insulator grown on the antiferromagnetic insulator Cr2O3. The exchange coupling between the two materials is investigated using field-cooling-dependent magnetometry and polarized neutron reflectometry. Both techniques reveal strong interfacial interaction between the antiferromagnetic order of the Cr2O3 and the magnetic topological insulator, manifested as an exchange bias when the sample is field-cooled under an out-of-plane magnetic field, and an exchange spring-like magnetic depth profile when the system is magnetized within the film plane. These results identify antiferromagnetic insulators as suitable candidates for the manipulation of magnetic and topological order in topological insulator films. 相似文献
7.
Rui Sun Shijia Yang Xu Yang A. Kumar Eric Vetter Wenhua Xue Yan Li Na Li Yang Li Shihao Zhang Binghui Ge Xiang-qun Zhang Wei He Alexander F. Kemper Dali Sun Zhao-hua Cheng 《Advanced materials (Deerfield Beach, Fla.)》2020,32(49):2005315
Emergent topological insulators (TIs) and their design are in high demand for manipulating and transmitting spin information toward ultralow-power-consumption spintronic applications. Here, distinct topological states with tailored spin properties can be achieved in a single reduced-dimensional TI-superlattice, (Bi2/Bi2Se3)-(Bi2/Bi2Se3)N or (□/Bi2Se3)-(Bi2/Bi2Se3)N (N is the repeating unit, □ represents an empty layer) by controlling the termination via molecular beam epitaxy. The Bi2-terminated superlattice exhibits a single Dirac cone with a spin momentum splitting ≈0.5 Å−1, producing a pronounced inverse Edelstein effect with a coherence length up to 1.26 nm. In contrast, the Bi2Se3-terminated superlattice is identified as a dual TI protected by coexisting time reversal and mirror symmetries, showing an unexpectedly long spin lifetime up to 1 ns. The work elucidates the key role of dimensionality and dual topological phases in selecting desired spin properties, suggesting a promise route for engineering topological superlattices for high-performance TI-spintronic devices. 相似文献
8.
Qisheng Wang Feng Wang Jie Li Zhenxing Wang Xueying Zhan Jun He 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(36):4613-4624
Topological crystalline insulators (TCIs) are recently discovered topological phase with robust surface states residing on high‐symmetry crystal surfaces. Different from conventional topological insulators (TIs), protection of surface states on TCIs comes from point‐group symmetry instead of time‐reversal symmetry in TIs. The distinct properties of TCIs make them promising candidates for the use in novel spintronics, low‐dissipation quantum computation, tunable pressure sensor, mid‐infrared detector, and thermoelectric conversion. However, similar to the situation in TIs, the surface states are always suppressed by bulk carriers, impeding the exploitation of topology‐induced quantum phenomenon. One effective way to solve this problem is to grow low‐dimensional TCIs which possess large surface‐to‐volume ratio, and thus profoundly increase the carrier contribution from topological surface states. Indeed, through persistent effort, researchers have obtained unique quantum transport phenomenon, originating from topological surface states, based on controllable growth of low‐dimensional TCIs. This article gives a comprehensive review on the recent progress of controllable synthesis and topological surface transport of low‐dimensional TCIs. The possible future direction about low‐dimensional TCIs is also briefly discussed at the end of this paper. 相似文献
9.
Electromagnetic scattering from a topological insulator (TI) cylinder buried beneath a rough surface is considered. To account for the interactions of the scattered field and the rough surface, spectral plane wave representation of fields is used along with small perturbation method. Both time-reversal symmetry TI cylinder and time-reversal symmetry broken TI cylinder are considered to evaluate the scattered-transmitted field above the rough surface for different values of the periods of the rough surface and the size of the object. It is observed that co- and cross-polarized field components show a maximum before the time-reversal symmetry is broken. The co-polarized component remains almost constant while the cross-polarized component decreases for time-reversal symmetry broken case. 相似文献
10.
Hannes Herrmann Peter Hlawenka Konrad Siemensmeyer Eugen Weschke Jaime Sánchez-Barriga Andrei Varykhalov Natalya Y. Shitsevalova Anatoliy V. Dukhnenko Volodymyr B. Filipov Slavomir Gabáni Karol Flachbart Oliver Rader Martin Sterrer Emile D. L. Rienks 《Advanced materials (Deerfield Beach, Fla.)》2020,32(10):1906725
SmB6 has recently attracted considerable interest as a candidate for the first strongly correlated topological insulator. Such materials promise entirely new properties such as correlation-enhanced bulk bandgaps or a Fermi surface from spin excitations. Whether SmB6 and its surface states are topological or trivial is still heavily disputed however, and a solution is hindered by major disagreement between angle-resolved photoemission (ARPES) and scanning tunneling microscopy (STM) results. Here, a combined ARPES and STM experiment is conducted. It is discovered that the STM contrast strongly depends on the bias voltage and reverses its sign beyond 1 V. It is shown that the understanding of this contrast reversal is the clue to resolving the discrepancy between ARPES and STM results. In particular, the scanning tunneling spectra reflect a low-energy electronic structure at the surface, which supports a trivial origin of the surface states and the surface metallicity of SmB6. 相似文献
11.
Yanjun Ma Anthony Edgeton Hanjong Paik Brendan D. Faeth Christopher T. Parzyck Betül Pamuk Shun-Li Shang Zi-Kui Liu Kyle M. Shen Darrell G. Schlom Chang-Beom Eom 《Advanced materials (Deerfield Beach, Fla.)》2020,32(34):2000809
Topological materials are derived from the interplay between symmetry and topology. Advances in topological band theories have led to the prediction that the antiperovskite oxide Sr3SnO is a topological crystalline insulator, a new electronic phase of matter where the conductivity in its (001) crystallographic planes is protected by crystallographic point group symmetries. Realization of this material, however, is challenging. Guided by thermodynamic calculations, a deposition approach is designed and implemented to achieve the adsorption-controlled growth of epitaxial Sr3SnO single-crystal films by molecular-beam epitaxy (MBE). In situ transport and angle-resolved photoemission spectroscopy measurements reveal the metallic and electronic structure of the as-grown samples. Compared with conventional MBE, the used synthesis route results in superior sample quality and is readily adapted to other topological systems with antiperovskite structures. The successful realization of thin films of Sr3SnO opens opportunities to manipulate topological states by tuning symmetries via strain engineering and heterostructuring. 相似文献
12.
Xiaoyu Che Quanjun Pan Božo Vareskic Jingyi Zou Lei Pan Peng Zhang Gen Yin Hao Wu Qiming Shao Peng Deng Kang L. Wang 《Advanced materials (Deerfield Beach, Fla.)》2020,32(16):1907661
The topological surface states (TSS) in topological insulators (TIs) can exert strong spin–orbit torque (SOT) on adjacent magnetization, offering great potential in implementing energy-efficient magnetic memory devices. However, there are large discrepancies among the reported spin Hall angle values in TIs, and its temperature dependence still remains elusive. Here, the spin Hall angle in a modulation-doped Cr-BixSb2−xTe3 (Cr-BST) film is quantitatively determined via both transport and optic approaches, where consistent results are obtained. A large spin Hall angle of ≈90 in the modulation-doped Cr-BST film is demonstrated at 2.5 K, and the spin Hall angle drastically decreases to 0.3–0.5 as the temperature increases. Moreover, by tuning the top TSS carrier concentration, a competition between the top and bottom TSS in contributing to SOT is observed. The above phenomena can account for the large discrepancies among the previously reported spin Hall angle values and reveal the unique role of TSS in generating SOT. 相似文献
13.
Minggang Xie Chunguang Li Siqi Zhang Zhe Zhang Yuxin Li Xiao-Bo Chen Zhan Shi Shouhua Feng 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(33):2301436
The development of fast charging materials offers a viable solution for large-scale and sustainable energy storage needs. However, it remains a critical challenge to improve the electrical and ionic conductivity for better performance. Topological insulator (TI), a topological quantum material that has attracted worldwide attention, hosts unusual metallic surface states and consequent high carrier mobility. Nevertheless, its potential in promising high-rate charging capability has not been fully realized and explored. Herein, a novel Bi2Se3-ZnSe heterostructure as excellent fast charging material for Na+ storage is reported. Ultrathin Bi2Se3 nanoplates with rich TI metallic surfaces are introduced as an electronic platform inside the material, which greatly reduces the charge transfer resistance and improves the overall electrical conductivity. Meanwhile, the abundant crystalline interfaces between these two selenides promote Na+ migration and provide additional active sites as well. As expected, the composite delivers the excellent high-rate performance of 360.5 mAh g−1 at 20 A g−1 and maintains its electrochemical stability of 318.4 mAh g−1 after 3000 long cycles, which is the record high for all reported selenide-based anodes. This work is anticipated to provide alternative strategies for further exploration of topological insulators and advanced heterostructures. 相似文献
14.
Zhibin Wu Gemeng Liang Wei Kong Pang Tengfei Zhou Zhenxiang Cheng Wenchao Zhang Ye Liu Bernt Johannessen Zaiping Guo 《Advanced materials (Deerfield Beach, Fla.)》2020,32(2):1905632
Topological insulators have spurred worldwide interest, but their advantageous properties have scarcely been explored in terms of electrochemical energy storage, and their high-rate capability and long-term cycling stability still remain a significant challenge to harvest. p-Type topological insulator SnSb2Te4 nanodots anchoring on few-layered graphene (SnSb2Te4/G) are synthesized as a stable anode for high-rate lithium-ion batteries and potassium-ion batteries through a ball-milling method. These SnSb2Te4/G composite electrodes show ultralong cycle lifespan (478 mAh g−1 at 1 A g−1 after 1000 cycles) and excellent rate capability (remaining 373 mAh g−1 even at 10 A g−1) in Li-ion storage owing to the rapid ion transport accelerated by the PN heterojunction, virtual electron highways provided by the conductive topological surface state, and extraordinary pseudocapacitive contribution, whose excellent phase reversibility is confirmed by synchrotron in situ X-ray powder diffraction. Surprisingly, durable lifespan even at practical levels of mass loading (>10 mg cm−2) for Li-ion storage and excellent K-ion storage performance are also observed. This work provides new insights for designing high-rate electrode materials by boosting conductive topological surfaces, atomic doping, and the interface interaction. 相似文献
15.
Yingxi Bai Ning Mao Runhan Li Ying Dai Baibiao Huang Chengwang Niu 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(14):2206574
The understanding and manipulate of the second-order corner states are central to both fundamental physics and future topotronics applications. Despite the fact that numerous second-order topological insulators (SOTIs) are achieved, the efficient engineering in a given material remains elusive. Here, the emergence of 2D multiferroics SOTIs in SbAs and BP5 monolayers is theoretically demonstrated, and an efficient and straightforward way for engineering the nontrivial corner states by ferroelasticity and ferroelectricity is remarkably proposed. With ferroelectric polarization of SbAs and BP5 monolayers, the nontrivial corner states emerge in the mirror symmetric corners and are perpendicular to orientations of the in-plane spontaneous polarization. And remarkably the spatial distribution of the corner states can be effectively tuned by a ferroelastic switching. At the intermediate states of both ferroelectric and ferroelastic switchings, the corner states disappear. These finding not only combines exotic SOTIs with multiferroics but also pave the way for experimental discovery of 2D tunable SOTIs. 相似文献
16.
Qile Li Iolanda Di Bernardo Johnathon Maniatis Daniel McEwen Amelia Dominguez-Celorrio Mohammad T. H. Bhuiyan Mengting Zhao Anton Tadich Liam Watson Benjamin Lowe Thi-Hai-Yen Vu Chi Xuan Trang Jinwoong Hwang Sung-Kwan Mo Michael S. Fuhrer Mark T. Edmonds 《Advanced materials (Deerfield Beach, Fla.)》2024,36(24):2312004
Quantum anomalous Hall (QAH) insulators transport charge without resistance along topologically protected chiral 1D edge states. Yet, in magnetic topological insulators to date, topological protection is far from robust, with zero-magnetic field QAH effect only realized at temperatures an order of magnitude below the Néel temperature TN, though small magnetic fields can stabilize QAH effect. Understanding why topological protection breaks down is therefore essential to realizing QAH effect at higher temperatures. Here a scanning tunneling microscope is used to directly map the size of exchange gap (Eg,ex) and its spatial fluctuation in the QAH insulator 5-layer MnBi2Te4. Long-range fluctuations of Eg,ex are observed, with values ranging between 0 (gapless) and 70 meV, appearing to be uncorrelated to individual surface point defects. The breakdown of topological protection is directly imaged, showing that the gapless edge state, the hallmark signature of a QAH insulator, hybridizes with extended gapless regions in the bulk. Finally, it is unambiguously demonstrated that the gapless regions originate from magnetic disorder, by demonstrating that a small magnetic field restores Eg,ex in these regions, explaining the recovery of topological protection in magnetic fields. The results indicate that overcoming magnetic disorder is the key to exploiting the unique properties of QAH insulators. 相似文献
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18.
Hao Wu Felix Groß Bingqian Dai David Lujan Seyed Armin Razavi Peng Zhang Yuxiang Liu Kemal Sobotkiewich Johannes Förster Markus Weigand Gisela Schütz Xiaoqin Li Joachim Gräfe Kang L. Wang 《Advanced materials (Deerfield Beach, Fla.)》2020,32(34):2003380
Magnetic skyrmions are topologically nontrivial chiral spin textures that have potential applications in next-generation energy-efficient and high-density spintronic devices. In general, the chiral spins of skyrmions are stabilized by the noncollinear Dzyaloshinskii–Moriya interaction (DMI), originating from the inversion symmetry breaking combined with the strong spin–orbit coupling (SOC). Here, the strong SOC from topological insulators (TIs) is utilized to provide a large interfacial DMI in TI/ferrimagnet heterostructures at room temperature, resulting in small-size (radius ≈ 100 nm) skyrmions in the adjacent ferrimagnet. Antiferromagnetically coupled skyrmion sublattices are observed in the ferrimagnet by element-resolved scanning transmission X-ray microscopy, showing the potential of a vanishing skyrmion Hall effect and ultrafast skyrmion dynamics. The line-scan spin profile of the single skyrmion shows a Néel-type domain wall structure and a 120 nm size of the 180° domain wall. This work demonstrates the sizable DMI and small skyrmions in TI-based heterostructures with great promise for low-energy spintronic devices. 相似文献
19.
Ye Zhang Feng Zhang Yiguo Xu Weichun Huang Leiming Wu Zhijun Dong Yupeng Zhang Biqing Dong Xiuwen Zhang Han Zhang 《Small Methods》2019,3(12)
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. 相似文献
20.
Yujing Liu Min Tang Mengmeng Meng Mingzhan Wang Jinxiong Wu Jianbo Yin Yubing Zhou Yunfan Guo Congwei Tan Wenhui Dang Shaoyun Huang H. Q. Xu Yong Wang Hailin Peng 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(18)
Nanostructures of ternary topological insulator (TI) Bi2Te2Se are, in principle, advantageous to the manifestation of topologically nontrivial surface states, due to significantly enhanced surface‐to‐volume ratio compared with its bulk crystals counterparts. Herein, the synthesis of 2D Bi2Te2Se crystals on mica via the van der Waals epitaxy method is explored and systematically the growth behaviors during the synthesis process are investigated. Accordingly, 2D Bi2Te2Se crystals with domain size up to 50 µm large and thickness down to 2 nm are obtained. A pronounced weak antilocalization effect is clearly observed in the 2D Bi2Te2Se crystals at 2 K. The method for epitaxial growth of 2D ternary Bi2Te2Se crystals may inspire materials engineering toward enhanced manifestation of the subtle surface states of TIs and thereby facilitate their potential applications in next‐generation spintronics. 相似文献