Single Channel Josephson Effect in a High Transmission Atomic Contact

Senkpiel, Jacob; Dambach, Simon; Etzkorn, Markus; Drost, Robert; Padurariu, Ciprian; Kubala, Björn; Belzig, Wolfgang; Yeyati, Alfredo Levy; Cuevas, Juan Carlos; Ankerhold, Joachim; Ast, Christian R.; Kern, Klaus

doi:10.48550/arxiv.1810.10609

Cited by 2 publications

(3 citation statements)

References 18 publications

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“…2(c) as blue circles. It follows a (1 − τ 1 ) dependence as veri ed through the linear t. is nding of pronounced single-channel characteristics in a junction between two Al atoms is consistent with previous experimental results obtained using the subgap structure of the current in the superconducting state [36].…”

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confidence: 91%

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Dynamical Coulomb Blockade as a Local Probe for Quantum Transport

et al. 2020

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antum uctuations are imprinted with valuable information about transport processes. Experimental access to this information is possible, but challenging. We introduce the dynamical Coulomb blockade (DCB) as a local probe for uctuations in a scanning tunneling microscope (STM) and show that it provides information about the conduction channels. In agreement with theoretical predictions, we nd that the DCB disappears in a single-channel junction with increasing transmission following the Fano factor, analogous to what happens with shot noise. Furthermore we demonstrate local di erences in the DCB expected from changes in the conduction channel con guration. Our experimental results are complemented by ab initio transport calculations that elucidate the microscopic nature of the conduction channels in our atomic-scale contacts. We conclude that probing the DCB by STM provides a technique complementary to shot noise measurements for locally resolving quantum transport characteristics.An important consequence of the downscaling of electronic circuits towards the atomic limit is the emergence of charge quantization e ects [1][2][3][4][5]. e concomitant quantum uctuations of charge and phase carry valuable information about transport processes [6], such as channel conguration, spin polarization, or e ective charge [7][8][9][10][11][12][13][14][15][16]. Accessing them experimentally, however, for instance through shot-noise measurements [17] is quite challenging, but feasible [18][19][20][21][22][23]. Alternatively, the dynamical Coulomb blockade (DCB) is also a consequence of quantum uctuations. It arises from the inelastic interaction of tunneling electrons with the local electromagnetic environment [24][25][26][27][28][29], in which the junction is embedded [see Fig. 1(a)]. It appears when the thermal energy k B T , with the temperature T and the Boltzmann constant k B , is on the order of or smaller than the charging energy E C = e 2 /2C J , with the elementary charge e = |e |, associated with the capacitance C J of the tunnel junction. e DCB is directly observable in di erential conductance data, where it manifests itself as a dip in the voltage range on the order of E C /e around zero bias [30-33], as, for example, at very low temperatures ( 1 K) in small capacitance (few fF) mesoscopic circuits [26][27][28][29][30][31][32][33][34][35].In this Le er, we exploit the DCB in ultra-low temperature scanning tunneling spectroscopy (STS) as a tool to locally identify the quantum transport characteristics of atomicscale junctions all the way from the tunnel to the contact regime. First, we use a junction formed between two single atoms featuring a single dominant transport channel [36]. e DCB is seen at low transmission, but disappears with increasing transmission following the Fano factor for a singlechannel junction [37]. Extending the measurements to a junction between a single atom on one side and two atoms on the other side, we nd a di erent signature in the DCB dip. is indicates a direct in uence of the number of tra...

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confidence: 91%

“…In this Le er, we exploit the DCB in ultra-low temperature scanning tunneling spectroscopy (STS) as a tool to locally identify the quantum transport characteristics of atomicscale junctions all the way from the tunnel to the contact regime. First, we use a junction formed between two single atoms featuring a single dominant transport channel [36].…”

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Dynamical Coulomb Blockade as a Local Probe for Quantum Transport

et al. 2020

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“…YSR states have been observed on a variety of magnetic atoms -intrinsically present or deliberately placed on the surface -on various superconducting substrates using scanning tunneling microscopy (STM) [11][12][13][14][15]. Due to its capabilities to resolve and manipulate single atoms [7,[16][17][18][19], the STM is ideally suited to realize a tunable coupling between one YSR state at the tip apex and another on the sample surface. Elementary charges tunneling between these two YSR states results in subgap excitations that subsequently relax into the continuum of each superconductor acting as a reservoir.…”

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Tunneling dynamics between superconducting bound states at the atomic limit

Huang,

Padurariu,

Senkpiel

et al. 2019

Preprint

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Despite plenty of room at the bo om, there is a limit to the miniaturization of every process. For charge transport this is realized by the coupling of single discrete energy levels at the atomic scale. Here, we demonstrate sequential tunneling between parity protected Yu-Shiba-Rusinov (YSR) states bound to magnetic impurities located on the superconducting tip and sample of a scanning tunneling microscope at 10 mK. We reduce the relaxation of the excited YSR state to the bare minimum and nd an enhanced lifetime for single quasiparticle levels. Our work o ers a way to characterize and to manipulate coupled superconducting bound states, such as Andreev levels, YSR states, or Majorana bound states.

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Single Channel Josephson Effect in a High Transmission Atomic Contact

Cited by 2 publications

References 18 publications

Dynamical Coulomb Blockade as a Local Probe for Quantum Transport

Dynamical Coulomb Blockade as a Local Probe for Quantum Transport

Tunneling dynamics between superconducting bound states at the atomic limit

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