Superconducting Transition and Critical Field of Pure Gallium Single Crystals

Gregory, W. D.; Sheahen, Thomas P.; Cochran, J. F.

doi:10.1103/physrev.150.315

Cited by 34 publications

(11 citation statements)

References 9 publications

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“…Therfore, Ga/GaN may possibly serve an ideal system to search for enhanced superconductivity near their interface. In this work, by in situ scanning tunneling microscopy/spectroscopy (STM/STS), ex situ electrical magneto-transport and magnetization measurements, we have unambiguously demonstrated that two-monolayer (ML) Ga films (as thin as 0.552 nm) grown on GaN form a hexagonal structure and exhibit superconductivity with a T c up to 5.4 K, which differs from any previously reported stable or crystalline Ga phases [18][19][20]. The anisotropy of critical magnetic field and Berezinski-Kosterlitz-Thouless (BKT)-like transition are observed, indicative of the 2D nature of superconductivity in 2 ML Ga/GaN(0001).…”

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confidence: 57%

“…, indicative of a strong coupling superconductor for 2 ML Ga/GaN(0001) [18]. Figure 2(c) illustrates the dI/dV spectra as a function of the applied magnetic field normal to the sample surface (B ⊥ ).…”

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confidence: 99%

“…GaN, as a wide band gap and high piezo-electric constant semiconductor [13,14], is commonly used in highspeed transistors, lasers for telecommunications, and light-emitting diodes for energy efficient displays. More significantly, it has been previously shown that GaN is often wetted with one to two atomic layers of Ga atoms [15][16][17], wherein Ga is intrinsically superconductive [18][19][20]. Therfore, Ga/GaN may possibly serve an ideal system to search for enhanced superconductivity near their interface.…”

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Detection of a Superconducting Phase in a Two-Atom Layer of Hexagonal Ga Film Grown on Semiconducting GaN(0001)

Zhang

Sun

et al. 2015

Phys. Rev. Lett.

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The recent observation of superconducting state at atomic scale has motivated the pursuit of exotic condensed phases in two-dimensional (2D) systems. Here we report on a superconducting phase in two-monolayer crystalline Ga films epitaxially grown on wide band-gap semiconductor GaN(0001). This phase exhibits a hexagonal structure and only 0.552 nm in thickness, nevertheless, brings about a superconducting transition temperature Tc as high as 5.4 K, confirmed by in situ scanning tunneling spectroscopy, and ex situ electrical magneto-transport and magnetization measurements. The anisotropy of critical magnetic field and Berezinski-Kosterlitz-Thouless-like transition are observed, typical for the 2D superconductivity. Our results demonstrate a novel platform for exploring atomic-scale 2D superconductor, with great potential for understanding of the interface superconductivity.PACS numbers: 68.37. Ef, 74.55.+v, Superconductivity has recently been observed in oneatomic-layer Pb [1][2][3][4][5] and In [6,7] films grown on Si(111) substrate, at the SrTiO 3 /LaAlO 3 interface [8], and in one-unit-cell thick FeSe films on SrTiO 3 [9,10]. This has been stimulating great attention and interest for both understanding the electron pairing in quantum confined systems and also the pursuit of emergent phases of matter in the two-dimensional (2D) systems, such as the enhancement of superconducting transition temperature T c . The recent discovery of electric field induced superconductivity at SrTiO 3 surface [11] and in 2D MoS 2 crystal [12] further demonstrates the feasibility of controlling 2D superconductivity via interface engineering. Thus far, however, the nature of interface or 2D superconductivity remains obscure. Preparing more hybird heterostructures with enhanced superconductivity is particularly required but experimentally challenging.GaN, as a wide band gap and high piezo-electric constant semiconductor [13,14], is commonly used in highspeed transistors, lasers for telecommunications, and light-emitting diodes for energy efficient displays. More significantly, it has been previously shown that GaN is often wetted with one to two atomic layers of Ga atoms [15][16][17], wherein Ga is intrinsically superconductive [18][19][20]. Therfore, Ga/GaN may possibly serve an ideal system to search for enhanced superconductivity near their interface. In this work, by in situ scanning tunneling microscopy/spectroscopy (STM/STS), ex situ electrical magneto-transport and magnetization measurements, we have unambiguously demonstrated that two-monolayer (ML) Ga films (as thin as 0.552 nm) grown on GaN form a hexagonal structure and exhibit superconductivity with a T c up to 5.4 K, which differs from any previously reported stable or crystalline Ga phases [18][19][20]. The anisotropy of critical magnetic field and BerezinskiKosterlitz-Thouless (BKT)-like transition are observed, indicative of the 2D nature of superconductivity in 2 ML Ga/GaN(0001).Our STM/STS experiments are conducted in a Unisoku ultrahigh vacuum low temperature STM ...

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Detection of a Superconducting Phase in a Two-Atom Layer of Hexagonal Ga Film Grown on Semiconducting GaN(0001)

Zhang

Sun

et al. 2015

Phys. Rev. Lett.

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“…Сопоставляя с теорией температурную зависимость Н к (при не очень низких температурах) Ga 81 обратной длины свободного пробега электрона 1~1 (не-зависимо от сорта примеси) в разбавленных твердых растворах сверхпроводников с немагнитными примесями (см., напри-мер, 19 ' 81 ). Идея о том, что учет изотропного рассеяния электронов на примесных центрах может привести к сглаживанию анизотропии щели по мере приближения к условию Ι ~ ξ (где ξ -длина когерентно-сти), впервые была предложена Андерсоном 21 .…”

Section: г = 2^(^) (-г)unclassified

Gap anisotropy in the energy spectrum of superconductors

Shepelev¹

1968

Usp. Fiz. Nauk

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Микроскопическая теория Бардина, Купера, Шриффера 1 и Боголю-бова 2 объяснила явление сверхпроводимости возникновением в энерге-тическом спектре металла вблизи поверхности Ферми области запрещен-ных электронных состояний, что связано с появлением в сверхпроводнике ниже температуры перехода электронных пар с противоположными импуль-сами и спинами. Образование пар происходит за счет обмена виртуальными фононами и наступает в том случае, когда связанное с этим электрон-фононным взаимодействием притяжение электронов гдев в -температура Дебая ме-Рпс _ t . теоретическая зависимость величины талла, N (0) -плотность элек-энергетической щели в спектре сверхпровод-тронных состояний на поверх-ника от температуры *. ности Ферми в нормальном со-стоянии металла, V -матричный элемент взаимодействия квазичастиц. Для возбуждения сверхпроводника при 0° К необходим разрыв пары квазичастиц с затратой энергии, минимальное значение которой равно 2Δ (0). В сверхпроводнике энергия квазичастиц, подчиняющихся стати-стике Ферми, равна E q = (е\ -f-Δη) 1 / 2 , где e q -энергия квазичастиц в нормальном металле, отсчитываемая от уровня Ферми, а Δ 4 -параметр энергетической щели, зависящий, в общем случае, от направления вол-нового вектора квазичастицы q и e q . На рис. 2 приведена зависимость Е^ в сверхпроводящем состоянии металла от волнового вектора q. Плот-ность одночастичных состояний в сверхпроводнике определяется сле-дующим соотношением:

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“…Many different gallium allotropes are known to harbor superconductivity. Both the bulk α-phase and the metastable β-phase are superconducting, with critical temperatures (T c ) of 1.1 and 6.0 K respectively [11,12]. Ultrathin Ga films grown epitaxially on GaN have also been found to be superconducting, with a T c of 4 − 5 K [13,14], and are notably the first system where a quantum Griffiths singularity, due to disorder, was observed at the superconductor-metal transition [14].…”

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Superconductivity in gallenene

Petrov¹,

Bekaert²,

Miloševıć³

2021

2D Mater.

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Among the large variety of two-dimensional (2D) materials discovered to date, elemental monolayers that host superconductivity are very rare. Using ab initio calculations we show that recently synthesized gallium monolayers, coined gallenene, are intrinsically superconducting through electron-phonon coupling. We reveal that Ga-100 gallenene, a planar monolayer isostructural with graphene, is the structurally simplest 2D superconductor to date, furthermore hosting topological edge states due to its honeycomb structure. Our anisotropic Eliashberg calculations show distinctly three-gap superconductivity in Ga-100, in contrast to the alternative buckled Ga-010 gallenene which presents a single anisotropic superconducting gap. Strikingly, the critical temperature (Tc) of gallenene is in the range of 7 − 10 K, exceeding the Tc of bulk gallium from which it is exfoliated. Finally we explore chemical functionalization of gallenene with hydrogen, and report induced multigap superconductivity with an enhanced Tc in the resulting gallenane compound.

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Superconducting Transition and Critical Field of Pure Gallium Single Crystals

Cited by 34 publications

References 9 publications

Detection of a Superconducting Phase in a Two-Atom Layer of Hexagonal Ga Film Grown on Semiconducting GaN(0001)

Detection of a Superconducting Phase in a Two-Atom Layer of Hexagonal Ga Film Grown on Semiconducting GaN(0001)

Gap anisotropy in the energy spectrum of superconductors

Superconductivity in gallenene

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