<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si0070.gif" overflow="scroll"><mml:mrow><mml:mn>0</mml:mn><mml:mo>−</mml:mo><mml:mi>π</mml:mi></mml:mrow></mml:math>Quantum transition in a carbon nanotube Josephson junction: Universal phase dependence and orbital degeneracy

Delagrange, R.; Weil, Raphaël; Kasumov, A.; Ferrier, M.; Bouchiat, H.; Deblock, R.

doi:10.1016/j.physb.2017.09.034

Cited by 27 publications

(19 citation statements)

References 95 publications

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“…2c for a junction in the diffusive regime, (that is, with a mean free path shorter than the length L ). While the CPR of atomic point contacts20, nanowire-based quantum dots212223 and graphene24 have previously been measured in this way, the CPR of micrometre-long, quasi-ballistic channels has, to our knowledge, not been accessed.…”

Section: Resultsmentioning

confidence: 99%

Ballistic edge states in Bismuth nanowires revealed by SQUID interferometry

et al. 2017

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The protection against backscattering provided by topology is a striking property. In two-dimensional insulators, a consequence of this topological protection is the ballistic nature of the one-dimensional helical edge states. One demonstration of ballisticity is the quantized Hall conductance. Here we provide another demonstration of ballistic transport, in the way the edge states carry a supercurrent. The system we have investigated is a micrometre-long monocrystalline bismuth nanowire with topological surfaces, that we connect to two superconducting electrodes. We have measured the relation between the Josephson current flowing through the nanowire and the superconducting phase difference at its ends, the current–phase relation. The sharp sawtooth-shaped phase-modulated current–phase relation we find demonstrates that transport occurs selectively along two ballistic edges of the nanowire. In addition, we show that a magnetic field induces 0–π transitions and φ0-junction behaviour, providing a way to manipulate the phase of the supercurrent-carrying edge states and generate spin supercurrents.

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Section: Resultsmentioning

confidence: 99%

Ballistic edge states in Bismuth nanowires revealed by SQUID interferometry

et al. 2017

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“…A first method consists in the study of the current-phase relation, which can be measured in asymmetric SQUIDs [98,99]. By tuning the electron density via a gate, the goal is to identify the contribution of the topological modes.…”

Section: Future Objectivesmentioning

confidence: 99%

Microwave Studies of the Fractional Josephson Effect in HgTe-Based Josephson Junctions

et al. 2018

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The rise of topological phases of matter is strongly connected to their potential to host Majorana bound states, a powerful ingredient in the search for a robust, topologically protected, quantum information processing. In order to produce such states, a method of choice is to induce superconductivity in topological insulators. The engineering of the interplay between superconductivity and the electronic properties of a topological insulator is a challenging task and it is consequently very important to understand the physics of simple superconducting devices such as Josephson junctions, in which new topological properties are expected to emerge.In this article, we review recent experiments investigating topological superconductivity in topological insulators, using microwave excitation and detection techniques. More precisely, we have fabricated and studied topological Josephson junctions made of HgTe weak links in contact with Al or Nb contacts. In such devices, we have observed two signatures of the fractional Josephson effect, which is expected to emerge from topologically-protected gapless Andreev bound states.We first recall the theoretical background on topological Josephson junctions, then move to the experimental observations. Then, we assess the topological ori-

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“…In a second experiment, the existence of a non-local current-phase relation can be directly determined by measurements of the switching current. This type of experiment has been performed on superconducting atomic contacts 35 , graphene 36 and carbon nanotubes 37 . As shown in Figure 4…”

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confidence: 99%

Nonlocal Josephson Effect in Andreev Molecules

et al. 2019

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We propose the "Andreev molecule," an artificial quantum system composed of two closely spaced Josephson junctions. The coupling between Josephson junctions in an Andreev molecule occurs through the overlap and hybridization of the junction's "atomic" orbitals, Andreev Bound States. A striking consequence is that the supercurrent flowing through one junction depends on the superconducting phase difference across the other junction. Using the Bogolubiov-de-Gennes formalism, we derive the energy spectrum and non-local current-phase relation for arbitrary separation. We demonstrate the possibility of creating a ϕ-junction and propose experiments to verify our predictions. Andreev molecules may have potential applications in quantum information, metrology, sensing, and molecular simulation. 1 arXiv:1809.11011v3 [cond-mat.mes-hall] 4 Sep 2019 Keywords superconductivity, Josephson junction, Andreev bound states, superconducting circuits, quantum informationUnderstanding and exploiting the interaction between Josephson junctions is paramount for superconducting device applications in quantum information 1 , magnetometry 2 , metrology 3 , and quantum simulation 4 . In typical superconducting circuits, junctions interact indirectly via electromagnetic coupling to inductors, capacitors, transmission lines, and microwave resonators. In addition to this well understood long-range interaction 5 , there is a short range interaction via quasiparticle diffusion which can modify superconducting energy gaps and critical currents, but is only important close to T c , the superconducting transition temperature, or at large bias voltages 6 .A second short-range interaction, mediated by Cooper pairs, is relevant to the majority of applications where characteristic energies are much smaller than the gap, but is still poorly understood. It becomes significant when the distance between Josephson junctions is comparable to ξ 0 , the superconducting coherence length, and can modify the electrical properties in a dramatic way.Initially, minor effects resulting from this "order-parameter interaction" were calculated for temperatures near T c using the Ginzburg-Landau equations 7 . More recently, theorists have investigated this problem at arbitrary temperature using Green's function techniques.In the two-electrode geometry, where it is not possible to independently apply a phase difference to each junction, the overall current-phase relation and dc current were obtained 8,9 .For the more relevant three-electrode geometry, non-local out-of-equilibrium supercurrents were calculated and the existence of π shifts in the current-phase relation were demonstrated 10-15 . A remarkable phase-locking similar to Shapiro steps was predicted and subsequently measured experimentally in superconducting bi-junctions biased with commensurate voltages 16,17 . The authors attribute these phenomena to the formation of entangled Cooper pairs called "quartets."

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0−πQuantum transition in a carbon nanotube Josephson junction: Universal phase dependence and orbital degeneracy

Cited by 27 publications

References 95 publications

Ballistic edge states in Bismuth nanowires revealed by SQUID interferometry

Ballistic edge states in Bismuth nanowires revealed by SQUID interferometry

Microwave Studies of the Fractional Josephson Effect in HgTe-Based Josephson Junctions

Nonlocal Josephson Effect in Andreev Molecules

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