Josephson junction dynamics in the presence of 
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-periodic supercurrents

Domínguez, Fernándo; Kashuba, Oleksiy; Bocquillon, Erwann; Wiedenmann, Jonas; Deacon, Russell; Klapwijk, T. M.; Platero, Gloria; Molenkamp, Laurens W.; Trauzettel, Björn; Hankiewicz, Ewelina M.

doi:10.1103/physrevb.95.195430

Cited by 76 publications

(66 citation statements)

References 48 publications

(143 reference statements)

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“…In contrast with the standard oscillatory behavior with a complete suppression at the resistive nodes, the even steps, including the supercurrent branch (n = 0), exhibit a non-vanishing amplitude at every two resistive node on increasing P rf , see Fig. 3c and d. This unusual feature has been predicted in a recent paper by Domínguez et al [26]. It is a direct consequence of the presence of the 4π-periodic channel.…”

Section: Resultsmentioning

confidence: 56%

“…To phenomenologically capture the complex dynamics of a topological Josephson junction where a MBS lies within (a majority of) ABS's, we include two different Josephson junctions J1 and J2 in the RSJ model (see Fig. 3a) [24,26]. The first junction J1 stands for the conventional ABS's with a 2π-periodic current-phase relation, and the second one J2 represents the 4π-periodic MBS's.…”

Section: Resultsmentioning

confidence: 99%

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Joule overheating poisons the fractional ac Josephson effect in topological Josephson junctions

et al. 2019

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Topological Josephson junctions designed on the surface of a 3D-topological insulator (TI) harbor Majorana bound states (MBS's) among a continuum of conventional Andreev bound states. The distinct feature of these MBS's lies in the 4π-periodicity of their energy-phase relation that yields a fractional ac Josephson effect and a suppression of odd Shapiro steps under rf irradiation. Yet, recent experiments showed that a few, or only the first, odd Shapiro steps are missing, casting doubts on the interpretation. Here, we show that Josephson junctions tailored on the large bandgap 3D TI Bi2Se3 exhibit a fractional ac Josephson effect acting on the first Shapiro step only. With a modified resistively shunted junction model, we demonstrate that the resilience of higher order odd Shapiro steps can be accounted for by thermal poisoning driven by Joule overheating. Furthermore, we uncover a residual supercurrent at the nodes between Shapiro lobes, which provides a direct and novel signature of the current carried by the MBS's. Our findings showcase the crucial role of thermal effects in topological Josephson junctions and lend support to the Majorana origin of the partial suppression of odd Shapiro steps.Topological superconductivity engineered by coupling superconducting electrodes to topological states of matter has attracted considerable attention due to the prospect of manipulating Majorana states for topological quantum computing [1][2][3].Intense experimental efforts have focused on spectroscopic signatures of Majorana bound states (MBS's) in various superconductivity-proximitized systems, including semiconducting nanowires [4][5][6][7][8], atomic chains [9,10] or islands [11] of magnetic atoms, and vortices at the surface of 3D TI's [12].Another key approach to substantiate the very existence of MBS relies on the fractional ac Josephson effect [13][14][15] that develops in topological Josephson junction [3,15]. Theory predicts that MBS's shall emerge in such junctions as a peculiar, spinless Andreev bound state (ABS). Contrary to the conventional ABS's whose energy level varies 2π-periodically with the phase difference φ between the junction electrodes, the MBS is 4πperiodic and crosses zero-energy for a phase π (see Fig. 1a), yielding a fractional ac Josephson effect at frequency f J /2 = eV /h (e is the electron charge, V the voltage drop across the junction and h the Planck constant), that is, half the Josephson frequency f J [3,15].Yet, revealing such a 4π-periodic contribution has proven challenging in dc transport experiments due to the presence of often prevailing, conventional ABS's [16][17][18]. Moreover, poisoning processes -stochastic paritychanges of the quasiparticle occupation number -may obscure the MBS contribution by limiting its lifetime [19,20]. Measurement schemes probing at timescales shorter than this lifetime are thus essential. The Shapiro effect comes forth with the combined advantages of a radiofrequency (f rf ) excitation of the phase that can be faster than the poisoning dynamics [15,21...

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Section: Resultsmentioning

confidence: 56%

Section: Resultsmentioning

confidence: 99%

Joule overheating poisons the fractional ac Josephson effect in topological Josephson junctions

et al. 2019

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“…However, it is much more difficult to compute at the same elementary level the time-dependent response to a bias voltage or current, that emerges from the non-linear Josephson equations [76,77], especially in the currentbias situation that is experimentally most relevant. To simulate the response of our devices, we turn to the RSJ model [78,79,73], in which we incorporate both 2πand 4π-periodic supercurrents [33,52,57,80].…”

Section: Modeling Of a Topological Josephson Junction With 2π-and 4π-mentioning

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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“…To distinguish the beating phenomenon in topological situation from the one caused by the presence of usual Andreev states it may be helpful to study the behavior of the beating frequency as a function of system parameters, gate potentials and magnetic field so that to reveal the features peculiar to the topologically protected levels. The beating phenomenon may also affect non-stationary Josephson-type transport in systems with MBS studied in recent experiments [34,35].…”

Section: Discussion and Outlookmentioning

confidence: 95%

Nonlocality and dynamic response of Majorana states in fermionic superfluids

2017

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We suggest a microscopic model describing the nonlocal ac response of a pair of Majorana states in fermionic superfluids beyond the tunneling approximation. The time-dependent perturbations of quasiparticle transport are shown to excite finite period beating of the wavefunction between the distant Majorana states. We propose an experimental test to measure the characteristic time scales of quasiparticle transport through the pair of Majorana states defining, thus, quantitative characteristics of nonlocality known to be a generic feature of Majorana particles.

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Josephson junction dynamics in the presence of 2π - and 4π -periodic supercurrents

Cited by 76 publications

References 48 publications

Joule overheating poisons the fractional ac Josephson effect in topological Josephson junctions

Joule overheating poisons the fractional ac Josephson effect in topological Josephson junctions

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

Nonlocality and dynamic response of Majorana states in fermionic superfluids

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