Two-Dimensional Superconductor with a Giant Rashba Effect: One-Atom-Layer Tl-Pb Compound on Si(111)

Matetskiy, A. V.; Ichinokura, Satoru; Bondarenko, L. V.; Tupchaya, A. Y.; Грузнев, Д. В.; Зотов, А. В.; Саранин, А. А.; Hobara, Rei; Takayama, A.; Hasegawa, Shuji

doi:10.1103/physrevlett.115.147003

Cited by 117 publications

(113 citation statements)

References 42 publications

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“…1 c and e). In addition, we estimate electron-phonon coupling constant to be 0.5±0.2 for the hole band [35], which agrees with our transport result by fitting the upper critical field data ( Fig. 2 b).…”

supporting

confidence: 89%

“…d, Energy width of the hole band as a function of temperature for a 3-Sn/10-PbTe sample. The electron-phonon coupling constant is estimated from a linear fitting (solid line) to the data points[35]. The estimated electron phonon coupling constant is 0.5±0.2 with the uncertainty obtained by taking into account both the Lorentzian and the linear fittings involved (see Extended DataFigure 4).…”

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confidence: 96%

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Superconductivity in few-layer stanene

et al. 2018

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A single atomic slice of α -tin-stanene-has been predicted to host the quantum spin Hall effect at room temperature, offering an ideal platform to study low-dimensional and topological physics. Although recent research has focused on monolayer stanene, the quantum size effect in few-layer stanene could profoundly change material properties, but remains unexplored. By exploring the layer degree of freedom, we discover superconductivity in few-layer stanene down to a bilayer grown on PbTe, while bulk α -tin is not superconductive. Through substrate engineering, we further realize a transition from a single-band to a two-band superconductor with a doubling of the transition temperature. In situ angleresolved photoemission spectroscopy (ARPES) together with first-principles calculations elucidate the corresponding band structure. The theory also indicates the existence of a topologically non-trivial band. Our experimental findings open up novel strategies for constructing two-dimensional topological superconductors.Confining superconductivity to a two-dimensional (2D) plane engenders a variety of quantum phenomena 1,2 . Of late, the realization of highly crystalline and atomically thin superconductors has triggered a flurry of discoveries, including the Griffiths singularity behavior 3 and a quantum metallic phase 4,5 , as well as an extremely large critical magnetic field in the plane 6,7 . One strategy for achieving 2D superconductors is to epitaxially grow superconductive single elements, such as Pb, In and Ga, for just one or two atomic layers 3,8,9 . Among the single elements, tin (Sn) is the very material in which the Meissner effect was first discovered 10 , but realizing ultrathin Sn in the superconductive β -phase, known as white tin 11 , remains challenging. The epitaxially grown Sn in the ultrathin limit tends to fall instead in the α -phase 12 , whose bulk is semi-metallic and non-superconductive.Recently, however, intensive research has been devoted to investigate the thinnest possible slice of α -tin (111) ) is the focus of current research. On the other hand, few-layer stanene is expected to show significant thicknessdependent properties due to the strong quantum confinement 20 , but its exploration is still lacking.In this Letter, by going from monolayer to few-layer stanene, surprisingly, we discover superconductivity. We report the stable superconducting properties of uncapped few-layer stanene films on PbTe (111)/Bi 2 Te 3 substrates. The superconducting transition temperature (T c ) can be effectively enhanced by varying the thickness of the PbTe buffer layer. Concomitantly with a doubling of T c , we observe a single-band to two-band transition, which is further elucidated by photoemission spectroscopy and theoretical calculations. The calculated band structure further indicates the existence of inverted bands in our system. Our results therefore underscore the potential of an in-plane integration of 2Dtopological insulator and superconductor-of the same material. The heterostructure, vertically...

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confidence: 96%

Superconductivity in few-layer stanene

et al. 2018

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“…This state is called the helical state [98]. The FFLO-like state and the helical state compete with each other [99], but the helical state is more robust against the [52]. The same surface also showed a superconducting transition at 2.25 K, opening a route for investigating exotic superconducting state as stated above.…”

Section: Metal Atomic Layers On Semiconductor Surfacesmentioning

confidence: 75%

Two-dimensional superconductors with atomic-scale thickness

Uchihashi

2016

Supercond. Sci. Technol.

120

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Recent progress in two-dimensional superconductors with atomic-scale thicknesses is reviewed mainly from the experimental point of view. The superconducting systems treated here involve a variety of materials and forms: elemental-metal ultrathin films and atomic layers on semiconductor surfaces; interfaces and superlattices of heterostructures made of cuprates, perovskite oxides, and rareearth metal heavy-fermion compounds; interfaces of electric-double-layer transistors; graphene and atomic sheets of transition-metal dichalcogenide; iron selenide and organic conductors on oxide and metal surfaces, respectively. Unique phenomena arising from the ultimate two-dimensionality of the system and the physics behind them are discussed.Contents in the atomic-scale limit has been a technical challenge for a long time. This is because, in this limit, the whole system consists entirely of surfaces and interfaces, which are vulnerable to structural and chemical disorder in general. For this purpose, therefore, it is demanded that samples with highly ordered and controlled surfaces and interfaces should be fabricated and their superconducting properties probed through advanced techniques.During this decade, the studies on ultrathin 2D superconductors have seen remarkable progress beyond the traditional experimental framework in various fields, and the existence of 2D superconductors with truly atomic-scale thicknesses has also been established. This was mostly driven by rapid advancements on nanotechnology in recent years, including molecular beam epitaxy (MBE), pulsed laser deposition (PLD), in-situ ultrahigh vacuum (UHV)-low temperature (LT) measurement, scanning tunneling microscopy/spectroscopy (STM/STS), etc. These technologies now allow various types of superconducting materials to be fabricated with the atomic-scale precision and to be characterized in unprecedented details, which will be the subject of the present review article. For example, ultrathin elemental metal films grown on silicon surfaces in a layer-by-layer fashion were found to exhibit robust superconductivity down the monolayer (ML) thickness regime [17,18]. This system also exhibits Tc oscillation as a function of film thickness due to the electron quantum confinement effects [19]. La2-xSrxCuO4, a representative cuprate high-Tc superconductor, also showed superconductivity at one-unit-cell (1-UC) thickness and was electrically tuned to an insulating state, revealing a S-I transition driven by quantum phase fluctuations [20]. Furthermore, the interface between LaAlO3 and SrTiO3, both of them being perovskite oxide insulators, was found to exhibit 2D superconductivity that can coexist or compete with ferromagnetism [21]. Recent technological breakthrough of field-effect transistors (FET) using an electric-double-layer (EDL) gate have enabled carrier doping with an unprecedentedly high level (n2D ~10 14 cm -2 ) at the subsurface region [22]. This led to the successful realization of field-induced 2D superconductivity in various insulating materials includi...

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“…The wide range of quantum metallic state under magnetic field observed in EDLT and exfoliated 2D superconductors has not been clearly observed in oxide interfaces 21,165 or MBEgrown ordered-metal atomic layers 86 . This may be because of the unintentional deficiencies, grain boundaries or surface atomic steps, which are inevitably included during the film growth process and can become strong pinning centers even in highly-crystalline materials.…”

Section: Quantum Metallic State In Highly-crystalline 2d Superconductorsmentioning

confidence: 96%

Highly crystalline 2D superconductors

2016

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Recent technological advances in controlling materials have developed methods to produce idealized two-dimensional (2D) electron systems such as heterogeneous interfaces, molecularbeam-epitaxy (MBE) grown atomic layers, exfoliated thin flakes and field-effect devices.These 2D electron systems are highly-crystalline with less disorder in common, some of which indeed show sheet resistance more than one order of magnitude lower even in atomic layers or single layers than that of conventional amorphous/granular thin films. Here, we present a review on the recent developments of highly-crystalline 2D superconductors and a series of unprecedented physical properties discovered in these systems. In particular, we highlight the quantum metallic state (or possible metallic ground state), the quantum Griffiths phase in outof-plane magnetic fields, and the superconducting state maintained in anomalously large inplane magnetic fields, which were observed in exfoliated 2D materials, MBE-grown atomiclayer thin films and electric-double-layer (ion-gated) interfaces. These phenomena are discussed on the basis of weakened disorder and/or broken spatial inversion symmetry. These novel aspects suggest that highly-crystalline 2D systems are promising platforms for exploring new quantum physics and superconductors.

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Two-Dimensional Superconductor with a Giant Rashba Effect: One-Atom-Layer Tl-Pb Compound on Si(111)

Cited by 117 publications

References 42 publications

Superconductivity in few-layer stanene

Superconductivity in few-layer stanene

Two-dimensional superconductors with atomic-scale thickness

Highly crystalline 2D superconductors

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