Adaptive tuning of Majorana fermions in a quantum dot chain

Fulga, Ion Cosma; Haim, Arbel; Akhmerov, A. R.; Oreg, Yuval

doi:10.1088/1367-2630/15/4/045020

Cited by 95 publications

(97 citation statements)

References 44 publications

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“…Results presented here imply that the breaking of the underlying symmetries can be achieved in superconductorquantum dot structures while maintaining coherent transport of Cooper pairs. In this context, our experiment is directly related to the efforts of studying triplet superconductivity and superconducting spintronics 26 as well as in achieving topological superconducting phase in quantum dots coupled to an s-wave superconductor 16,[27][28][29][30][31][32] . Aside from that, a gate-tunable phase offset may open novel possibilities for the realization of electrically controlled flux-and phase-based quantum bits 33 , superconducting computer memory components 34 , as well as superconducting 'phase' batteries and rectifiers 4,35 .…”

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confidence: 99%

Josephson ϕ0-junction in nanowire quantum dots

et al. 2016

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The Josephson e ect describes supercurrent flowing through a junction connecting two superconducting leads by a thin barrier 1 . This current is driven by a superconducting phase di erence ϕ between the leads. In the presence of chiral and time-reversal symmetry of the Cooper pair tunnelling process 2 , the current is strictly zero when ϕ vanishes. Only if these underlying symmetries are broken can the supercurrent for ϕ = 0 be finite [3][4][5] . This corresponds to a ground state of the junction being o set by a phase ϕ 0 , di erent from 0 or π. Here, we report such a Josephson ϕ 0 -junction based on a nanowire quantum dot. We use a quantum interferometer device to investigate phase o sets and demonstrate that ϕ 0 can be controlled by electrostatic gating. Our results may have far-reaching implications for superconducting flux-and phase-defined quantum bits as well as for exploring topological superconductivity in quantum dot systems.The process of Cooper pair tunnelling through a Josephson junction (JJ) is, in general, symmetric with respect to time inversion. This has a profound consequence for the JJ current-phase relation, I (ϕ). In particular it imposes the condition I (−ϕ) = −I (ϕ), which in turn results in I (ϕ = 0) being strictly zero. The I (ϕ = 0) = 0 condition is a consequence of the fact that for each process contributing to current flowing in one direction there is an opposite time-reversed process, in which spin-up and spin-down electrons are reversed, that exactly cancels this current. However, time inversion is not the only symmetry which can protect the I (ϕ = 0) = 0 condition. For example, in JJs based on single-domain ferromagnets, time inversion is broken, but the supercurrent is still zero for ϕ = 0 owing to chiral symmetry-that is, the symmetry between leftward and rightward tunnelling. This symmetry ensures that the tunnelling coefficient describing the electron tunnelling from the left lead to the right lead is exactly the same as the one describing the tunnelling in reverse, from the right lead to the left lead. The two tunnelling processes (leftward and rightward) cancel each other, which again results in I (ϕ = 0) being strictly zero. This is even the case for so-called π-junctions 6 , in which the current flow is reversed compared to usual JJs, but still the underlying symmetries guarantee zero current for ϕ = 0. To create conditions for a non-zero supercurrent to flow at ϕ = 0, both symmetries need to be broken 7 . Various ways have been proposed theoretically to break the underlying symmetries and create ϕ 0 -junctions, including ones based on non-centrosymmetric or multilayer ferromagnets 3,8 , quantum point contacts 4 , topological insulators 9,10 , diffusive systems 11,12 , nanowires 13,14 and quantum dots 5,15,16 . Alternatively, an effective built-in phase offset can be obtained by combining 0-and π-junctions in parallel 17,18 . However, no experimental demonstration of a ϕ 0 -junction has been reported until now.In quantum dots (QDs), breaking of both symmetries can be achiev...

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confidence: 99%

Josephson ϕ0-junction in nanowire quantum dots

et al. 2016

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“…Another proposed realization of the Kitaev chain consists in using semiconductor quantum dots coupled to superconducting grains [49]. In this setup the access to the other parameters is more suitable because the relations between the experimental and effective parameters ir more simple [50]. The advantage of our analytical approach is that it allows to easily predict the TQPTs at any frequency regime i.e., not only in the high frequency regime but also at intermediate and low frequencies.…”

Section: Driving the Tunnelingmentioning

confidence: 99%

Floquet engineering of long-rangep-wave superconductivity

et al. 2014

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Floquet Majorana Fermions appear as steady states at the boundary of time-periodic topological phases of matter. In this work, we theoretically study the main features of these exotic topological phases in the periodically driven one-dimensional Kitaev model. By controlling the ac fields, we can predict new topological phase transitions that should give rise to signatures of Majorana states in experiments. Moreover, the knowledge of the time-dependence of these Majorana states allows one to manipulate them. Our work contains a complete analysis of the monochromatic driving in different frequency regimes.

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“…In one regime is equivalent to the Kitaev model (with one edge mode at each edge) and in another regime displays two edge modes (winding number two) 40 , which are however of a fermionic type and not of Majorana type. Other possible realizations of the model are engineering the Rashba spin-orbit interaction by placing micromagnets [41][42][43][44][45][46][47] or quantum-dot array 48 . The realistic presence of longer range hoppings or pairings in a Kitaev like model leads to a multiplicity of edge Majorana modes and complex phase diagrams [49][50][51][52] .…”

Section: Introductionmentioning

confidence: 99%

4π Josephson currents in junctions of hybridized multiband superconductors

2017

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We study two-band one-dimensional superconducting chains of spinless fermions with inter and intra-band pairing. These bands hybridize and, depending on the relative angular momentum of their orbitals, the hybridization can be symmetric or anti-symmetric. The self-consistent competition between intra and inter-band superconductivity and how it is affected by the symmetry of the hybridization is investigated. In the case of anti-symmetric hybridization the intra and inter-band pairings do not coexist while in the symmetric case they do coexist and the interband pairing is shown to be dominant. The topological properties of the model are obtained through the topological invariant winding number and the presence of edge states. We find the existence of a topological phase due to the inter-band superconductivity and induced by symmetric hybridization. In this case we find a characteristic 4π-periodic Josephson current. In the case of anti-symmetric hybridization we also find a 4π-periodic Josephson current in the gapless inter-band superconducting phase, recently identified to be of Weyl-type.

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Adaptive tuning of Majorana fermions in a quantum dot chain

Cited by 95 publications

References 44 publications

Josephson ϕ0-junction in nanowire quantum dots

Josephson ϕ0-junction in nanowire quantum dots

Floquet engineering of long-rangep-wave superconductivity

4π Josephson currents in junctions of hybridized multiband superconductors

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