Topological edge states in a high-temperature superconductor FeSe/SrTiO3(001) film

Wang, Z. F.; Zhang, Huimin; Liu, Defa; Liu, Chong; Tang, Chenjia; Song, Canli; Zhong, Yong; Peng, Junping; Li, Fangsen; Nie, Caina; Wang, Lili; Zhou, X. J.; Ma, Xucun; Xue, Q. K.; Liu, Feng

doi:10.1038/nmat4686

Cited by 165 publications

(167 citation statements)

References 33 publications

(22 reference statements)

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“…4e. With the Fermi level aligned relative to the included ARPES map 28 , the gap is indicated by the two vertical red dashed lines. Also shown is a reference red curve C taken from a point deep inside the island.…”

Section: Resultsmentioning

confidence: 99%

Large quantum-spin-Hall gap in single-layer 1T′ WSe2

et al. 2018

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Two-dimensional (2D) topological insulators (TIs) are promising platforms for low-dissipation spintronic devices based on the quantum-spin-Hall (QSH) effect, but experimental realization of such systems with a large band gap suitable for room-temperature applications has proven difficult. Here, we report the successful growth on bilayer graphene of a quasi-freestanding WSe2 single layer with the 1T′ structure that does not exist in the bulk form of WSe2. Using angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy/spectroscopy (STM/STS), we observe a gap of 129 meV in the 1T′ layer and an in-gap edge state located near the layer boundary. The system′s 2D TI characters are confirmed by first-principles calculations. The observed gap diminishes with doping by Rb adsorption, ultimately leading to an insulator–semimetal transition. The discovery of this large-gap 2D TI with a tunable band gap opens up opportunities for developing advanced nanoscale systems and quantum devices.

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Section: Resultsmentioning

confidence: 99%

Large quantum-spin-Hall gap in single-layer 1T′ WSe2

et al. 2018

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“…Monolayer FeSe grown on a SrTiO 3 substrate has also emerged as a model system to support both QSH and superconductivity. However, due to doping from the substrate, the Fermi energy (E F ) is more than 500 meV higher than the non-trivial gap, making it less practical for applications 18 . 1T phase monolayer TMDCs MX 2 , M = (W, Mo) and X = (Te, Se, S), are theoretically predicted to be a promising new class of QSH insulators with large bandgap 10 .…”

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confidence: 99%

Quantum spin Hall state in monolayer 1T'-WTe2

et al. 2017

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A quantum spin Hall (QSH) insulator is a novel twodimensional quantum state of matter that features quantized Hall conductance in the absence of a magnetic field, resulting from topologically protected dissipationless edge states that bridge the energy gap opened by band inversion and strong spin-orbit coupling 1,2 . By investigating the electronic structure of epitaxially grown monolayer 1T'-WTe 2 using angle-resolved photoemission (ARPES) and first-principles calculations, we observe clear signatures of topological band inversion and bandgap opening, which are the hallmarks of a QSH state. Scanning tunnelling microscopy measurements further confirm the correct crystal structure and the existence of a bulk bandgap, and provide evidence for a modified electronic structure near the edge that is consistent with the expectations for a QSH insulator. Our results establish monolayer 1T'-WTe 2 as a new class of QSH insulator with large bandgap in a robust two-dimensional materials family of transition metal dichalcogenides (TMDCs).A two-dimensional (2D) topological insulator (TI), or a quantum spin Hall insulator, is characterized by an insulating bulk and a conductive helical edge state, in which carriers with different spins counter-propagate to realize a geometry-independent edge conductance 2e 2 /h (refs 1,2). The only scattering channel for such helical edge current is back scattering, which is prohibited by time reversal symmetry, making QSH insulators a promising material candidate for spintronic and other applications.The prediction of the QSH effect in HgTe quantum wells sparked intense research efforts to realize the QSH state [3][4][5][6][7][8][9][10][11] . So far only a handful of QSH systems have been fabricated, mostly limited to quantum well structures of three-dimensional (3D) semiconductors such as HgTe/CdTe (ref.3) and InAs/GaSb (ref. 6). Edge conduction consistent with a QSH state has been observed 3,6,12 . However, the behaviour under a magnetic field, where time reversal symmetry is broken, cannot be explained within our current understanding of the QSH effect 13,14 . There have been continued efforts to predict and investigate other material systems to further advance the understanding of this novel quantum phenomenon 5,[7][8][9]15 . So far, it has been difficult to make a robust 2D material with a QSH state, a platform needed for widespread study and application. The small bandgaps exhibited by many candidate systems, as well as their vulnerability to strain, chemical adsorption, and element substitution, make them impractical for advanced spectroscopic studies or applications. For example, a QSH insulator candidate stanene, a monolayer analogue of graphene for tin, grown on Bi 2 Se 3 becomes topologically trivial due to the modification of its band structure by the underlying substrate 11,16 . Free-standing Bi film with 2D bonding on a cleaved surface has shown edge conduction 9 , but its topological nature is still debated 17 . It takes 3D out-of-plane bonding with the substrate and large stra...

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“…While the EPC cannot be fully excluded as the pairing glue for SC condensation, the replica anomaly beyond SC region at least implies that there exists the phononic component uninvolved in electron pairing in 1-UC FeSe. [38][39][40][41]. Among these proposals, the calculated band dispersions based on the checkerboard AFM order best match the ARPES results [41].…”

Section: Pairing Interactionsmentioning

confidence: 86%

“…[38][39][40][41]. Among these proposals, the calculated band dispersions based on the checkerboard AFM order best match the ARPES results [41]. Note that the double-TiO x termination of SrTiO 3 has not been considered throughout all the calculations.…”

Section: Pairing Interactionsmentioning

confidence: 91%

Heterostructural one-unit-cell FeSe/SrTiO₃: from high-temperature superconductivity to topological states

Liu

Wang

2020

2D Mater.

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High-temperature superconductivity in one-unit-cell (1-UC) FeSe/SrTiO 3 heterostructure has become a research frontier in condensed-matter physics and material science. The superconducting transition temperature (T c ) of ultrathin FeSe film is significantly enhanced compared to its bulk counterpart and possibly approaches the liquid-nitrogen region according to in situ spectroscopic measurements. Particularly, the Fermi-surface topology of 1-UC FeSe consists of no hole pockets at Brillouin-zone center, which poses a great challenge to the well-accepted s ± -wave pairing nesting the sign-different electron-hole Fermi pockets in iron-based superconductors. In this review, we present the explorations of T c enhancement, electron pairing and topological phases in 1-UC FeSe/SrTiO 3 . The potential coexistence of high-temperature superconductivity and topological electronic states promotes such two-dimensional heterostructure as the candidate of next-generation connate high-temperature topological superconductor and/or topological-quantum-computation platform.

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Topological edge states in a high-temperature superconductor FeSe/SrTiO3(001) film

Cited by 165 publications

References 33 publications

Large quantum-spin-Hall gap in single-layer 1T′ WSe2

Large quantum-spin-Hall gap in single-layer 1T′ WSe2

Quantum spin Hall state in monolayer 1T'-WTe2

Heterostructural one-unit-cell FeSe/SrTiO₃: from high-temperature superconductivity to topological states

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Topological edge states in a high-temperature superconductor FeSe/SrTiO3(001) film

Cited by 165 publications

References 33 publications

Large quantum-spin-Hall gap in single-layer 1T′ WSe2

Large quantum-spin-Hall gap in single-layer 1T′ WSe2

Quantum spin Hall state in monolayer 1T'-WTe2

Heterostructural one-unit-cell FeSe/SrTiO3: from high-temperature superconductivity to topological states

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Product

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Heterostructural one-unit-cell FeSe/SrTiO₃: from high-temperature superconductivity to topological states