Resonant Andreev Spectroscopy in normal-Metal/thin-Ferromagnet/Superconductor Device: Theory and Application

Romeo, Francesco; Giubileo, Filippo; Citro, Roberta; Bartolomeo, Antonio Di; Attanasio, C.; Cirillo, C.; Polcari, A.; Romano, P.

doi:10.1038/srep17544

Cited by 10 publications

(9 citation statements)

References 50 publications

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“…The figures indicate that the positions of all OGS anomalies shift to lower bias voltages with increasing temperature and the structures disappear at T C ∼ 5.0 K for VH 0.05 and ∼4.5 K for VH 0.1 . Therefore, we fit the temperature dependence of these anomalies based on the BCS gap function Δ( T ) Figure c,d illustrates the OGS peaks, indicated by the black arrows in Figure a,b, for VH 0.05 and VH 0.1 , respectively.…”

Section: Resultsmentioning

confidence: 99%

Over-the-Gap Conductance Oscillations in Superconducting Vanadium Nanocontacts Induced by Hydrogen Impurities

Islam

Takata²,

Inagaki

et al. 2022

ACS Nano

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We have investigated the current–voltage (I–V) characteristics of Josephson junctions made by a low-temperature superconductor of vanadium (V) with a small amount of hydrogen (H) and deuterium (D) impurities using a mechanically controllable break junction (MCBJ) technique. Below the superconducting transition temperature T C , the differential conductance dI/dV spectra show distinct peaks within the superconducting gap, known as the subgap structure, which result from multiple Andreev reflections in pure V nanocontacts. Additionally, the H and D impurities in V nanocontacts induce several new conductance peaks outside the gap, referred to as an over-the-gap structures (OGSs). We found that the OGS peaks exhibit strong temperature dependence until the temperature is close to T C and follow the gap function predicted by BCS theory. When the contact diameter is changed at low temperature using the MCBJ technique, the OGS anomalies change almost linearly with the inverse of the contact diameter. In addition, the gap anomalies are significantly shifted outward by changing the positions of the H atoms through application of a high bias voltage between the contacts. The above features suggest that the OGS peaks are caused by the superconducting quasiparticle interference induced by H or D impurities and/or inhomogeneous structures in the nanocontacts.

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Section: Resultsmentioning

confidence: 99%

Over-the-Gap Conductance Oscillations in Superconducting Vanadium Nanocontacts Induced by Hydrogen Impurities

Islam

Takata²,

Inagaki

et al. 2022

ACS Nano

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“…PCAR experiments have been reported to study conventional BCS superconductors [ 53 ], high Tc cuprates (both hole doped and electron doped) [ 54 , 55 , 56 , 57 , 58 , 59 ], multiband superconductors [ 60 , 61 , 62 , 63 , 64 ], ruthenocuprates [ 65 ], iron-pnicniteds [ 66 ], heavy fermion superconductors [ 67 ], non-centrosymmetric superconductors [ 68 ], and topological superconductors [ 69 ]. This technique has also been successfully applied for precise measurements of the thickness and of the polarization in thin ferromagnetic/superconductor multilayers [ 70 , 71 , 72 , 73 , 74 , 75 ]. The PCAR technique consists of realizing a nano-contact between a tip-shaped normal-metal (N) electrode and a superconductor (S), thus forming a N/S nano-junction.…”

Section: Resultsmentioning

confidence: 99%

Transport and Point Contact Measurements on Pr1−xCexPt4Ge12 Superconducting Polycrystals

et al. 2020

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We performed a detailed investigation of the superconducting properties of polycrystalline Pr1−xCexPt4Ge12 pellets. We report the effect of Ce substitution, for x = 0.07, on magnetic field phase diagram H-T. We demonstrate that the upper critical field is well described by the Ginzburg–Landau model and that the irreversibility field line has a scaling behaviour similar to cuprates. We also show that for magnetic fields lower than 0.4 T, the activation energy follows a power law of the type ?−1/2, suggesting a collective pinning regime with a quasi-2D character for the Ce-doped compound with x = 0.07. Furthermore, by means of a point contact Andreev reflection spectroscopy setup, we formed metal/superconductor nano-junctions as small as tens of nanometers on the PrPt4Ge12 parent compound (x = 0). Experimental results showed a wide variety of conductance features appearing in the dI/dV vs. V spectra, all explained in terms of a modified Blonder–Tinkham–Klapwijk model considering a superconducting order parameter with nodal directions as well as sign change in the momentum space for the sample with x = 0. The numerical simulations of the conductance spectra also demonstrate that s-wave pairing and anisotropic s-waves are unsuitable for reproducing experimental data obtained at low temperature on the un-doped compound. Interestingly, we show that the polycrystalline nature of the superconducting PrPt4Ge12 sample can favour the formation of an inter-grain Josephson junction in series with the point contact junction in this kind of experiments.

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“…The procedure above can be used to find the transmission and reflection amplitudes of more complicated systems, for instance with two normal leads coupled to a superconductor [58][59][60][61][62] . In the NISIN junction, a superconductor of width d S is coupled via insulating barriers to two normal-metal leads.…”

Section: Superconducting Junctionsmentioning

confidence: 99%

Electron waiting times in hybrid junctions with topological superconductors

Burset

Flindt

2018

Sci Rep

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We investigate the waiting time distributions (WTDs) of superconducting hybrid junctions, considering both conventional and topologically nontrivial superconductors hosting Majorana bound states at their edges. To this end, we employ a scattering matrix formalism that allows us to evaluate the waiting times between the transmissions and reflections of electrons or holes. Specifically, we analyze normal-metal–superconductor (NIS) junctions and NISIN junctions, where Cooper pairs are spatially split into different leads. The distribution of waiting times is sensitive to the simultaneous reflection of electrons and holes, which is enhanced by the zero-energy state in topological superconductors. For the NISIN junctions, the WTDs of trivial superconductors feature a sharp dependence on the applied voltage, while for topological ones they are mostly independent of it. This particular voltage dependence is again connected to the presence of topological edge states, showing that WTDs are a promising tool for identifying topological superconductivity.

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Resonant Andreev Spectroscopy in normal-Metal/thin-Ferromagnet/Superconductor Device: Theory and Application

Cited by 10 publications

References 50 publications

Over-the-Gap Conductance Oscillations in Superconducting Vanadium Nanocontacts Induced by Hydrogen Impurities

Over-the-Gap Conductance Oscillations in Superconducting Vanadium Nanocontacts Induced by Hydrogen Impurities

Transport and Point Contact Measurements on Pr1−xCexPt4Ge12 Superconducting Polycrystals

Electron waiting times in hybrid junctions with topological superconductors

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