Crossover from Josephson Effect to Single Interface Andreev Reflection in Asymmetric Superconductor/Nanowire Junctions

Günel, H. Yusuf; Borgwardt, N.; Batov, I. E.; Hardtdegen, H.; Sladek, Kamil; Panaitov, G.; Grützmacher, Detlev; Schäpers, Thomas

doi:10.1021/nl501350v

Cited by 28 publications

(30 citation statements)

References 35 publications

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“…The authors of ref. [ 14 ] fabricated two types of symmetric S-c-S trilayers, Al-/InAs-nanowire-Al and Nb-InAs-nanowire-Nb junctions and measured the differential resistance d V /d I as a function of the voltage bias at various temperatures. At 0.4 K, the Al-based devices exhibited subharmonic gap features at V n = 2 Δ Al /(en); n is an integer.…”

Section: Introductionmentioning

confidence: 99%

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Anomalous Inner-Gap Structure in Transport Characteristics of Superconducting Junctions with Degraded Interfaces

Zhitlukhina¹,

Devyatov²,

Egorov³

et al. 2016

Nanoscale Res Lett

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Quantitative description of charge transport across tunneling and break-junction devices with novel superconductors encounters some problems not present or not as severe for traditional superconducting materials. In this work, we explain unexpected features in related transport characteristics as an effect of a degraded nanoscaled sheath at the superconductor surface. A model capturing the main aspects of the ballistic charge transport across hybrid superconducting structures with normally conducting nanometer-thick interlayers is proposed. The calculations are based on a scattering formalism taking into account Andreev electron-into-hole (and inverse) reflections at normal metal-superconductor interfaces as well as transmission and backscattering events in insulating barriers between the electrodes. Current-voltage characteristics of such devices exhibit a rich diversity of anomalous (from the viewpoint of the standard theory) features, in particular shift of differential-conductance maxima at gap voltages to lower positions and appearance of well-defined dips instead expected coherence peaks. We compare our results with related experimental data.

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Section: Introductionmentioning

confidence: 99%

“…1a in ref. [ 14 ]. Similar d V /d I measurements at T < 4 K for a typical Nb-based junction depicted in Fig.…”

Section: Introductionmentioning

confidence: 99%

Anomalous Inner-Gap Structure in Transport Characteristics of Superconducting Junctions with Degraded Interfaces

Zhitlukhina¹,

Devyatov²,

Egorov³

et al. 2016

Nanoscale Res Lett

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“…[11] As shown in Figure 3c, the SGS structures correspond to Δ/2e (cyan dashed line), Δ/3e (light-green dashed line), and gap edge (light-pink dashed line) are observed for junction 3. The shape of the gap and SGS has been shown to be influenced by the ratio of L/ξ N , [6,[11][12][13] where ξ N is the Bardeen-CooperSchrieffer coherence length. The SGS consists of a set of pronounced maxima in dV/dI at V = 2Δ/ne if L/ξ N << 1, but the amplitude of the SGS decreases by increasing the ratio of L/ξ N .…”

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confidence: 99%

On‐Chip Andreev Devices: Hard Superconducting Gap and Quantum Transport in Ballistic Nb–In_0.75Ga_0.25As‐Quantum‐Well–Nb Josephson Junctions

Delfanazari

Puddy

et al. 2017

Advanced Materials

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A superconducting hard gap in hybrid superconductor–semiconductor devices has been found to be necessary to access topological superconductivity that hosts Majorana modes (non‐Abelian excitation). This requires the formation of homogeneous and barrier‐free interfaces between the superconductor and semiconductor. Here, a new platform is reported for topological superconductivity based on hybrid Nb–In0.75Ga0.25As‐quantum‐well–Nb that results in hard superconducting gap detection in symmetric, planar, and ballistic Josephson junctions. It is shown that with careful etching, sputtered Nb films can make high‐quality and transparent contacts to the In0.75Ga0.25As quantum well, and the differential resistance and critical current measurements of these devices are discussed as a function of temperature and magnetic field. It is demonstrated that proximity‐induced superconductivity in the In0.75Ga0.25As‐quantum‐well 2D electron gas results in the detection of a hard gap in four out of seven junctions on a chip with critical current values of up to 0.2 µA and transmission probabilities of >0.96. The results, together with the large g‐factor and Rashba spin–orbit coupling in In0.75Ga0.25As quantum wells, which indeed can be tuned by the indium composition, suggest that the Nb–In0.75Ga0.25As–Nb system can be an excellent candidate to achieve topological phase and to realize hybrid topological superconducting devices.

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“…We have recently observed increased switching current for parallel double quantum dot Josephson junctions (DQDJJs) with Al electrodes when both dots are on resonance, indicating split but correlated Cooper pair tunneling through the two dots 15 . To further study the spin correlation in the split tunneling of paired electrons it is proposed to detect the phase factor in two path interference [16][17][18] , for which parallel double [19][20][21][22][23][24][25][26] . In this study we report the fabrication and characterization of Nb-based self-assembled QDJJs, in which gatetunable InAs single and double SAQDs are utilized.…”

Section: Textmentioning

confidence: 99%

Superconducting transport in single and parallel double InAs quantum dot Josephson junctions with Nb-based superconducting electrodes

Baba

Sailer

Deacon

et al. 2015

Applied Physics Letters

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We report conductance and supercurrent measurements for InAs single and parallel double quantum dot Josephson junctions contacted with Nb or NbTiN superconducting electrodes. Large superconducting gap energy, high critical field and large switching current are observed, all reflecting the features of Nb-based electrodes. For the parallel double dots we observe an enhanced supercurrent when both dots are on resonance, which may reflect split Cooper pair tunneling. TEXTInherently low-dimensional semiconductors, such as nanowires, nanotubes, and self-assembled quantum dots, are attractive research materials, because their natural geometries are suited to study anisotropic quantum effects, and they are easily combined with superconductors or ferromagnets to investigate hybrid quantum effects. In particular, by directly contacting self-assembled quantum dots (SAQDs) with normal metal electrodes, gate-tunable electronic properties of confined electrons have been revealed, such as anisotropic and tunable spin-orbit interaction 1,2 and g-factor 2,3 , and tunable Kondo-effect 4,5 . For hybrid devices contacted with superconducting electrodes various kinds of proximity induced quantum transport have been revealed, including non-dissipative , spectroscopy of Andreev energy levels 7,8 , and competition between superconducting proximity effect and Kondo screening 9,10 . In most of these studies aluminum (Al) is used for the superconducting contacts primarily because it is an easy material for making small but robust superconducting junctions with well-established nano-fabrication techniques. Though experiments on QD Josephson junctions (QDJJs) with Al electrodes have been very successful to date, the parameter space is restricted to low magnetic field and low temperature and in most devices the superconducting energy gap maybe small compared with other energy scales. A superconductor with a large superconducting gap and a high critical field would extend the parameter space that can be studied with QDJJs and open new possibilities to study devices in high magnetic fields. One area in which high T c leads may be of benefit is the study of Cooper-pair beam splitting with two quantum dots parallel coupled to a superconductor, which provides a source of non-local entangled electron pairs for quantum information processing and quantum electron optics. Although Cooper-pair splitting is confirmed in several studies [11][12][13][14] with InAs nanowire or carbon nanotube devices, to prove the maintenance of the spin-singlet correlation after pairsplitting remains challenging. We have recently observed increased switching current for parallel double quantum dot Josephson junctions (DQDJJs) with Al electrodes when both dots are on resonance, indicating split but correlated Cooper pair tunneling through the two dots 15 . To further study the spin correlation in the split tunneling of paired electrons it is proposed to detect the phase factor in two path interference [16][17][18] , for which parallel double [19][20][21][22][23]...

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Crossover from Josephson Effect to Single Interface Andreev Reflection in Asymmetric Superconductor/Nanowire Junctions

Cited by 28 publications

References 35 publications

Anomalous Inner-Gap Structure in Transport Characteristics of Superconducting Junctions with Degraded Interfaces

Anomalous Inner-Gap Structure in Transport Characteristics of Superconducting Junctions with Degraded Interfaces

On‐Chip Andreev Devices: Hard Superconducting Gap and Quantum Transport in Ballistic Nb–In_0.75Ga_0.25As‐Quantum‐Well–Nb Josephson Junctions

Superconducting transport in single and parallel double InAs quantum dot Josephson junctions with Nb-based superconducting electrodes

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Crossover from Josephson Effect to Single Interface Andreev Reflection in Asymmetric Superconductor/Nanowire Junctions

Cited by 28 publications

References 35 publications

Anomalous Inner-Gap Structure in Transport Characteristics of Superconducting Junctions with Degraded Interfaces

Anomalous Inner-Gap Structure in Transport Characteristics of Superconducting Junctions with Degraded Interfaces

On‐Chip Andreev Devices: Hard Superconducting Gap and Quantum Transport in Ballistic Nb–In0.75Ga0.25As‐Quantum‐Well–Nb Josephson Junctions

Superconducting transport in single and parallel double InAs quantum dot Josephson junctions with Nb-based superconducting electrodes

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On‐Chip Andreev Devices: Hard Superconducting Gap and Quantum Transport in Ballistic Nb–In_0.75Ga_0.25As‐Quantum‐Well–Nb Josephson Junctions