Josephson current at atomic scale: Tunneling and nanocontacts using a STM

Rodrigo, José A.; Crespo, V.; Vieira, S.

doi:10.1016/j.physc.2005.12.040

Cited by 13 publications

(10 citation statements)

References 18 publications

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“…The example in figure 10(a) shows that the curve with larger total conductance presents a slightly smaller zero bias peak. This behavior is very similar to the one observed in S-S nanocontacts [36], where it was seen that the value of the zero bias current depends mainly on the individual transmissions of the quantum channels, and not on the total conductance of the nanocontact. These observations are compatible with the analysis in [37], where the robustness of the Majorana signatures in high transparency situations was studied.…”

Section: Resultssupporting

confidence: 84%

Topological superconductivity in metallic nanowires fabricated with a scanning tunneling microscope

et al. 2013

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We report on several low-temperature experiments supporting the presence of Majorana fermions in superconducting lead nanowires fabricated with a scanning tunneling microscope (STM). These nanowires are the connecting bridges between the STM tip and the sample resulting from indentation-retraction processes. We show here that by a controlled tuning of the nanowire region, in which superconductivity is confined by applied magnetic fields, the conductance curves obtained in these situations are indicative of topological superconductivity and Majorana fermions. The most prominent feature of this behavior is the emergence of a zero bias peak in the conductance curves, superimposed on a background characteristic of the conductance between a normal metal and a superconductor in the Andreev regime. The zero bias peak emerges in some nanowires when a magnetic field larger than the lead bulk critical field is applied. This field drives one of the electrodes into the normal state while the other, the tip, remains superconducting on its apex. Meanwhile a topological superconducting state appears in the connecting nanowire of nanometric size.

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Section: Resultssupporting

confidence: 84%

Topological superconductivity in metallic nanowires fabricated with a scanning tunneling microscope

et al. 2013

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“…Occasionally, slight atomic rearrangements at the nanocontact take place. These rearrangements are seen as variations in the conductance and the Josephson current [28,29], which can be directly related to slight changes in the conduction channel arrangements through the contact and have no influence in the behavior discussed.…”

Section: -2mentioning

confidence: 99%

Topological Superconducting State of Lead Nanowires in an External Magnetic Field

et al. 2012

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Superconductors with an odd number of bands crossing the Fermi energy have topologically protected Andreev states at interfaces, including Majorana states in one-dimensional geometries. We propose here that repeated indentation of a Pb tip on a Pb substrate can lead to nanowires such that the resulting superconducting system has novel topological properties. We have analyzed a number of conductance curves obtained in different nanowires, and observe, in a few cases, very peculiar dependence of the critical current on magnetic field. In these cases, the form of multiple Andreev reflections observed at finite voltages are compatible with topological superconductivity. The nanowires give a low number of 1D channels, large spin orbit coupling, and a sizable Zeeman energy, provided that the applied magnetic field is higher than the Pb bulk critical field.

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“…With the growing interest in phenomena with extremely sharp spectral features on smaller and smaller energy scales, the demand for higher and higher spectroscopic energy resolution increases. Examples are the Kondo effect 4 , Yu–Shiba–Rusinov states 5 6 , Majorana fermions 7 , or the Josephson effect 8 9 10 11 , just to name a few. Aside from the obvious strategy of lowering the temperature to increase the energy resolution 12 , superconducting tips have successfully been conducted to circumvent the broadening effects of the Fermi function in the tunnelling process and greatly improve the energy resolution 6 13 .…”

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confidence: 99%

Sensing the quantum limit in scanning tunnelling spectroscopy

et al. 2016

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The tunnelling current in scanning tunnelling spectroscopy (STS) is typically and often implicitly modelled by a continuous and homogeneous charge flow. If the charging energy of a single-charge quantum sufficiently exceeds the thermal energy, however, the granularity of the current becomes non-negligible. In this quantum limit, the capacitance of the tunnel junction mediates an interaction of the tunnelling electrons with the surrounding electromagnetic environment and becomes a source of noise itself, which cannot be neglected in STS. Using a scanning tunnelling microscope operating at 15 mK, we show that we operate in this quantum limit, which determines the ultimate energy resolution in STS. The P(E)-theory describes the probability for a tunnelling electron to exchange energy with the environment and can be regarded as the energy resolution function. We experimentally demonstrate this effect with a superconducting aluminium tip and a superconducting aluminium sample, where it is most pronounced.

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Josephson current at atomic scale: Tunneling and nanocontacts using a STM

Cited by 13 publications

References 18 publications

Topological superconductivity in metallic nanowires fabricated with a scanning tunneling microscope

Topological superconductivity in metallic nanowires fabricated with a scanning tunneling microscope

Topological Superconducting State of Lead Nanowires in an External Magnetic Field

Sensing the quantum limit in scanning tunnelling spectroscopy

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