Observation of spin-momentum locked surface states in amorphous Bi2Se3

Corbae, Paul; Ciocys, Samuel; Varjas, Dániel; Kennedy, Ellis; Molina-Ruiz, M.; Griffin, Sinéad M.; Chen, Zhanghui; Wang, Lin‐Wang; Minor, Andrew M.; Scott, Mary; Grushin, Adolfo G.; Lanzara, Alessandra; Hellman, F.

doi:10.1038/s41563-022-01458-0

Cited by 49 publications

(26 citation statements)

References 46 publications

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“…This intuition is supported by the past literature, where the insulating properties of amorphous Sb 2 Te 3 , both in the bulk and surface, have been established as a key property in its role as a phase change memory (PCM) material [37][38][39] . The collapse of the topological state has also recently been inferred in disordered Sb 2 Te 3 thin films 34,36 , although the growth-induced disorder makes it difficult to achieve topdown patterning in that case.…”

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confidence: 92%

“…In practice, it is unclear which conditions apply in real solids. Recent theories are divided on this point for the prototypical chalcogenide family of TIs 33,34 where experimental information on the glassy state is also limited 35,36 . This motivated a detailed systematic experimental study of the electronic properties of Sb 2 Te 3 as it transforms from the crystalline state into a glass.…”

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confidence: 99%

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Top-down patterning of topological surface and edge states using a focused ion beam

Bake

Zhang

et al. 2023

Nat Commun

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The conducting boundary states of topological insulators appear at an interface where the characteristic invariant ℤ2 switches from 1 to 0. These states offer prospects for quantum electronics; however, a method is needed to spatially-control ℤ2 to pattern conducting channels. It is shown that modifying Sb2Te3 single-crystal surfaces with an ion beam switches the topological insulator into an amorphous state exhibiting negligible bulk and surface conductivity. This is attributed to a transition from ℤ2 = 1 → ℤ2 = 0 at a threshold disorder strength. This observation is supported by density functional theory and model Hamiltonian calculations. Here we show that this ion-beam treatment allows for inverse lithography to pattern arrays of topological surfaces, edges and corners which are the building blocks of topological electronics.

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confidence: 92%

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confidence: 99%

Top-down patterning of topological surface and edge states using a focused ion beam

Bake

Zhang

et al. 2023

Nat Commun

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“…Besides, from a device technological perspective, it is of interest to determine if topological protection may suffice to reveal signatures of topological transport in systems with large disorder, such as textured, polycrystalline or even amorphous CoSi thin films. Concerning the latter, a new research direction has recently sparked the search for possible exotic topological phases in amorphous systems, despite the absence of crystal symmetries. − Notably, amorphous topological metals have been predicted but remain undetected …”

Section: Introductionmentioning

confidence: 99%

Disorder-Induced Magnetotransport Anomalies in Amorphous and Textured Co_1–xSi_x Semimetal Thin Films

Molinari

Balduini

Rocchino

et al. 2023

ACS Appl. Electron. Mater.

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In recent times the chiral semimetal cobalt monosilicide (CoSi) has emerged as a prototypical, nearly ideal topological conductor hosting giant, topologically protected Fermi arcs. Exotic topological quantum properties have already been identified in CoSi bulk single crystals. However, CoSi is also known for being prone to intrinsic disorder and inhomogeneities, which, despite topological protection, risk jeopardizing its topological transport features. Alternatively, topology may be stabilized by disorder, suggesting the tantalizing possibility of an amorphous variant of a topological metal, yet to be discovered. In this respect, understanding how microstructure and stoichiometry affect magnetotransport properties is of pivotal importance, particularly in case of low-dimensional CoSi thin films and devices. Here we comprehensively investigate the magnetotransport and magnetic properties of ≈25 nm Co 1−x Si x thin films grown on a MgO substrate with controlled film microstructure (amorphous vs textured) and chemical composition (0.40 < x < 0.60). The resistivity of Co 1−x Si x thin films is nearly insensitive to the film microstructure and displays a progressive evolution from metallic-like (dρ xx /dT > 0) to semiconducting-like (dρ xx /dT < 0) regimes of conduction upon increasing the silicon content. A variety of anomalies in the magnetotransport properties, comprising for instance signatures consistent with quantum localization and electron−electron interactions, anomalous Hall and Kondo effects, and the occurrence of magnetic exchange interactions, are attributable to the prominent influence of intrinsic structural and chemical disorder. Our systematic survey brings to attention the complexity and the challenges involved in the prospective exploitation of the topological chiral semimetal CoSi in nanoscale thin films and devices.

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“…34−37 Recently, Corbae et al have evidenced the TI surface states in an amorphous Bi x Se 1−x film by angle-resolved photoemission spectroscopy (ARPES). 38 amorphous bismuthene systems, 39 showing that these materials may present topological properties. Moreover, the effects of various dopants in TIs have also been extensively studied.…”

Section: ■ Introductionmentioning

confidence: 99%

Room Temperature Spin-to-Charge Conversion in Amorphous Topological Insulating Gd-Alloyed Bi_xSe_1–x/CoFeB Bilayers

Sahu

Yang

Fan

et al. 2023

ACS Appl. Mater. Interfaces

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Disordered topological insulator (TI) films have gained intense interest by benefiting from both the TI’s exotic transport properties and the advantage of mass production by sputtering. Here, we report on the clear evidence of spin-charge conversion (SCC) in amorphous Gd-alloyed Bi x Se1–x (BSG)/CoFeB bilayers fabricated by sputtering, which could be related to the amorphous TI surface states. Two methods have been employed to study SCC in BSG (t BSG = 6–16 nm)/CoFeB(5 nm) bilayers with different BSG thicknesses. First, spin pumping is used to generate a spin current in CoFeB and detect SCC by the inverse Edelstein effect (IEE). The maximum SCC efficiency (SCE) is measured to be as large as 0.035 nm (IEE length λ IEE) in a 6 nm thick BSG sample, which shows a strong decay when t BSG increases due to the increase of BSG surface roughness. The second method is THz time-domain spectroscopy, which reveals a small t BSG dependence of SCE, validating the occurrence of a pure interface state-related SCC. Furthermore, our angle-resolved photoemission spectroscopy data show dispersive two-dimensional surface states that cross the bulk gap until the Fermi level, strengthening the possibility of SCC due to the amorphous TI states. Our studies provide a new experimental direction toward the search for topological systems in amorphous solids.

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Observation of spin-momentum locked surface states in amorphous Bi2Se3

Cited by 49 publications

References 46 publications

Top-down patterning of topological surface and edge states using a focused ion beam

Top-down patterning of topological surface and edge states using a focused ion beam

Disorder-Induced Magnetotransport Anomalies in Amorphous and Textured Co_1–xSi_x Semimetal Thin Films

Room Temperature Spin-to-Charge Conversion in Amorphous Topological Insulating Gd-Alloyed Bi_xSe_1–x/CoFeB Bilayers

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Observation of spin-momentum locked surface states in amorphous Bi2Se3

Cited by 49 publications

References 46 publications

Top-down patterning of topological surface and edge states using a focused ion beam

Top-down patterning of topological surface and edge states using a focused ion beam

Disorder-Induced Magnetotransport Anomalies in Amorphous and Textured Co1–xSix Semimetal Thin Films

Room Temperature Spin-to-Charge Conversion in Amorphous Topological Insulating Gd-Alloyed BixSe1–x/CoFeB Bilayers

Contact Info

Product

Resources

About

Disorder-Induced Magnetotransport Anomalies in Amorphous and Textured Co_1–xSi_x Semimetal Thin Films

Room Temperature Spin-to-Charge Conversion in Amorphous Topological Insulating Gd-Alloyed Bi_xSe_1–x/CoFeB Bilayers