Andreev spectroscopy of FeSexTe1 - x

Naoya Fujioka, Yoshiki Shirai, Yukihiro Miyamoto, Hironori Tachibana, Azusa Matsuda

    Research output: Contribution to journalArticle

    1 Citation (Scopus)

    Abstract

    We fabricated two types of junctions on the c-axis plane of FeSe0.2Te0.8 (Fe[Se,Te], Tc ∼ 13 K) crystals. In the superconductor/oxide/superconductor heterojunctions with a Pb film as a counter electrode, we found a large conductance peak centered at 0 V, and a gap-like feature, which has a much higher energy scale than those reported as a gap energy of Fe[Se,Te]. In spite of a large energy scale, their temperature dependence approximately follows a BCS curve, indicating they come from superconductivity of Fe[Se,Te]. Since these structures can be understood as the results of Andreev bound state at the S/N boundary and the interference effect in the normal metal [1], we tried to identify the effect of a normal layer by fabricating Fe[Se,Te]/Al/Al2O3/Pb junction. Here, we could realize a clean controlled S/N interface and the tunnel junction to investigate electronic properties of the Al slab. We found similar conductance spectra as those junctions without Al layer, giving a support that the anomalous conductance spectra come from the effect of the S/N interface. As expected, the energy scale of the observed features was reduced when the thickness of the normal metal was increased. The absence of Josephson current and the existence of an Andreev bound state may be a signature of the sign-reversal paring in Fe[Se,Te].

    Original languageEnglish
    Article number1252887
    Pages (from-to)28-32
    Number of pages5
    JournalPhysica C: Superconductivity and its Applications
    Volume518
    DOIs
    Publication statusPublished - 2015 Jul 6

    Fingerprint

    Metals
    Spectroscopy
    Temperature scales
    Oxide superconductors
    Tunnel junctions
    Superconductivity
    Electronic properties
    spectroscopy
    Superconducting materials
    Heterojunctions
    Energy gap
    tunnel junctions
    metals
    Crystals
    Electrodes
    energy
    heterojunctions
    counters
    slabs
    superconductivity

    Keywords

    • Andreev spectroscopy
    • Conductance spectroscopy
    • Iron-based superconductor
    • Tunnel junction

    ASJC Scopus subject areas

    • Condensed Matter Physics
    • Electrical and Electronic Engineering
    • Energy Engineering and Power Technology
    • Electronic, Optical and Magnetic Materials

    Cite this

    Andreev spectroscopy of FeSexTe1 - x . / Fujioka, Naoya; Shirai, Yoshiki; Miyamoto, Yukihiro; Tachibana, Hironori; Matsuda, Azusa.

    In: Physica C: Superconductivity and its Applications, Vol. 518, 1252887, 06.07.2015, p. 28-32.

    Research output: Contribution to journalArticle

    Fujioka, Naoya ; Shirai, Yoshiki ; Miyamoto, Yukihiro ; Tachibana, Hironori ; Matsuda, Azusa. / Andreev spectroscopy of FeSexTe1 - x In: Physica C: Superconductivity and its Applications. 2015 ; Vol. 518. pp. 28-32.
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    AB - We fabricated two types of junctions on the c-axis plane of FeSe0.2Te0.8 (Fe[Se,Te], Tc ∼ 13 K) crystals. In the superconductor/oxide/superconductor heterojunctions with a Pb film as a counter electrode, we found a large conductance peak centered at 0 V, and a gap-like feature, which has a much higher energy scale than those reported as a gap energy of Fe[Se,Te]. In spite of a large energy scale, their temperature dependence approximately follows a BCS curve, indicating they come from superconductivity of Fe[Se,Te]. Since these structures can be understood as the results of Andreev bound state at the S/N boundary and the interference effect in the normal metal [1], we tried to identify the effect of a normal layer by fabricating Fe[Se,Te]/Al/Al2O3/Pb junction. Here, we could realize a clean controlled S/N interface and the tunnel junction to investigate electronic properties of the Al slab. We found similar conductance spectra as those junctions without Al layer, giving a support that the anomalous conductance spectra come from the effect of the S/N interface. As expected, the energy scale of the observed features was reduced when the thickness of the normal metal was increased. The absence of Josephson current and the existence of an Andreev bound state may be a signature of the sign-reversal paring in Fe[Se,Te].

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