Evidence for the Electron-Phonon Interaction in the Superconductivity of a Transition Metal-Tantalum

Shen, L. Y. L.

doi:10.1103/physrevlett.24.1104

Cited by 76 publications

(32 citation statements)

References 25 publications

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“…STS reveals a superconducting energy gap Δ sample ≈ 0.63 meV of the substrate [ Fig. 1(e)] with a critical temperature T c ≈ 4 K [27] slightly smaller than the previously determined values (Δ ¼ 0.71 AE 0.02 meV, T c ¼ 4.5 AE 0.03 K) from planar tunnel junctions and resistivity measurements [35,36].Cold deposition of Fe results in a statistical distribution of single Fe adatoms, mostly adsorbed on top of the center of the plaquettes [ Fig. 1(b)], which we will focus on in the following.…”

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confidence: 97%

Spin-Resolved Spectroscopy of the Yu-Shiba-Rusinov States of Individual Atoms

et al. 2017

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A magnetic atom in a superconducting host induces so-called Yu-Shiba-Rusinov (YSR) bound states inside the superconducting energy gap. By combining spin-resolved scanning tunneling spectroscopy with simulations we demonstrate that the pair of peaks associated with the YSR states of an individual Fe atom coupled to an oxygen-reconstructed Ta surface gets spin polarized in an external magnetic field. As theoretically predicted, the electron and hole parts of the YSR states have opposite signs of spin polarizations which keep their spin character when crossing the Fermi level through the quantum phase transition. The simulation of a YSR state right at the Fermi level reveals zero spin polarization which can be used to distinguish such states from Majorana zero modes in chains of YSR atoms. DOI: 10.1103/PhysRevLett.119.197002 Recent investigations of chains [1][2][3] and arrays [4,5] of magnetic atoms in contact with surfaces of s-wave superconductors in view of Majorana zero modes and topological superconductivity triggered renewed interest in the properties of the basic constituent of such systems, the individual magnetic adatom. Typically, such adatoms induce quasiparticle excitations inside the superconducting energy gap [6][7][8], referred to as Yu-Shiba-Rusinov (YSR) states, which hamper the identification of topologically nontrivial edge states [3,9], calling for a thorough characterization of all experimentally accessible properties of YSR states.Following the first experimental verification of YSR states of individual atoms using scanning tunneling spectroscopy (STS) [10], there were numerous experimental studies, focusing on orbital effects [11][12][13], magnetic anisotropy [14], effects of reduced dimensionality of the superconductor [15], effects of coupling [11,16], and the competition between Kondo screening and superconducting pairing [17,18]. However, the investigation of the spin polarization of the YSR state of individual atoms, which could serve as a fingerprint for the distinction from topological states [19], was so far restricted to theoretical predictions [6][7][8][20][21][22].Neglecting orbital effects or magnetic anisotropy, theory predicts one pair of spin-polarized states of a YSR atom, an electron (e − )-and a hole (h)-like part with opposite spin character, which are located at AEjεj from the Fermi level E F [20]. There is a pronounced asymmetry in spectral weight between the e − and h parts due to electron-hole asymmetry of the band structure [21,22] and/or a nonmagnetic scattering potential of the impurity [20,23]. With increasing exchange coupling J between the adatom and substrate, the binding energy ε decreases until the YSR states eventually cross E F through a quantum phase transition (QPT), accompanied by an inversion of the asymmetry in the e − − h spectral weight [17]. Most notably, since both parts of the YSR states keep their spin character, the spin polarization above and below E F is expected to invert [20] through the QPT. Here, we experimentally verify these prediction...

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Spin-Resolved Spectroscopy of the Yu-Shiba-Rusinov States of Individual Atoms

et al. 2017

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“…Doch schon für die tbergangsmetall-Elemente wurde bisher eine detaillierte tunnelspektroskopische Untersuchung, die sich auf umfangreicheres, auch durch Reproduzierbarkeit gut gesichertes experimentelles Material stützen müßte, insbesondere was den Energiebereich der Phononenstrukturen betrifft, durch fast unüberwindlich scheinende Schwierigkeiten bei der Präparation der Tunnelkontakte verhindert. So gibt es neben den zahlreichen Veröffentlichungen über den Bereich der Energielücke 1-' nur drei Arbeiten [8][9][10] , in denen der Nachweis von Phononenstrukturen an einzelnen Proben überhaupt gelungen ist. …”

Section: Introductionunclassified

Ein neues Verfahren zur Präparation von Tantal/Silber und Niob/Silber Tunnel- kontakten / A New Method for the Preparation of Tantalum/Silver and Niobium/Silver Tunneling Contacts

Gärtner

1976

Zeitschrift Für Naturforschung A

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A New Method for the Preparation of Tantalum/Silver and Niobium/Silver Tunneling ContactsThe preparation starts from material in wire-form. One end of the wire is degassed under ultrahigh-vacuum conditions by a very simple electron-gun and finally melted to form a small smooth sphere. The tunneling barrier is formed by thermal oxidation of the investigated superconductor with oxygen under reduced pressure. The handling of the whole sample (masking and contacting procedures included) is very simple and allows to use this method for systematic tunneling-studies of the transition metal superconductors. Einleitung

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“…If the amplitude v^ is small, the series converges rapidly. The voltage output of the operational amplifier is given by 6v = v^e'"'^ + Rf 51 (27) Using Eqs. (25), (26) and (27) we can solve for 6v…”

Section: He-3 Cryostatmentioning

confidence: 99%

Electron tunneling and the proximity effect in Pb--Cd thin films

Toplicar

1976

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Evidence for the Electron-Phonon Interaction in the Superconductivity of a Transition Metal-Tantalum

Cited by 76 publications

References 25 publications

Spin-Resolved Spectroscopy of the Yu-Shiba-Rusinov States of Individual Atoms

Spin-Resolved Spectroscopy of the Yu-Shiba-Rusinov States of Individual Atoms

Ein neues Verfahren zur Präparation von Tantal/Silber und Niob/Silber Tunnel- kontakten / A New Method for the Preparation of Tantalum/Silver and Niobium/Silver Tunneling Contacts

Electron tunneling and the proximity effect in Pb--Cd thin films

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