Microwave spectroscopy of spinful Andreev bound states in ballistic semiconductor Josephson junctions

Woerkom, David J. van; Proutski, Alex; Heck, Bernard van; Bouman, Daniël; Väyrynen, Jukka I.; Glazman, L. I.; Krogstrup, Peter; Nygård, Jesper; Kouwenhoven, Leo P.; Geresdi, Attila

doi:10.1038/nphys4150

Cited by 126 publications

(142 citation statements)

References 44 publications

(90 reference statements)

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“…Topological superconductors (TSCs) supporting Majorana modes have been shown to demonstrate a 4π-periodic Josephson effect 4-10 , which is doubled period compared to the conventional Josephson effect. This phenomenon, which is known as the fractional Josephson effect, has been observed in quite a few devices 11,12 including the quantum spin Hall edge 13,14 . At first this is quite counter-intuitive given that the Hamiltonian itself is 2π-periodic.…”

Section: Introductionmentioning

confidence: 99%

8π -periodic dissipationless ac Josephson effect on a quantum spin Hall edge via a quantum magnetic impurity

Hui

2017

Phys. Rev. B

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Time-reversal invariance places strong constraints on the properties of the quantum spin Hall edge. One such restriction is the inevitability of dissipation in a Josephson junction between two superconductors formed on such an edge without the presence of interaction. Interactions and spinconservation breaking are key ingredients for the realization of dissipationless ac Josephson effect on such quantum spin Hall edges. We present a simple quantum impurity model that allows to create a dissipationless fractional Josephson effect on a quantum spin Hall edge. We then use this model to substantiate a general argument that shows that any such non-dissipative Josephson effect must necessarily be 8π-periodic.

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Section: Introductionmentioning

confidence: 99%

8π -periodic dissipationless ac Josephson effect on a quantum spin Hall edge via a quantum magnetic impurity

Hui

2017

Phys. Rev. B

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“…However, direct observations of these Majorana modes in quantum wires are challenging because of their intrinsic weak charge coupling. Indirect observations based on spectroscopy or interferometric measurements in proximitized semiconductor nanowire devices [14][15][16][17][18] or hybrid superconducting-quantum interference devices [19] are still debated as the signals are hard to distinguish from the contributions of other processes like Andreev bound states and the Kondo effect [18,20].…”

Section: Introductionmentioning

confidence: 99%

Sensing Floquet-Majorana fermions via heat transfer

2017

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Time periodic modulations of the transverse field in the closed XY spin-1 2 chain generate a very rich dynamical phase diagram, with a hierarchy of Z n topological phases characterized by differing numbers of Floquet-Majorana modes. This rich phase diagram survives when the system is coupled to dissipative end reservoirs. Circumventing the obstacle of preparing and measuring quasienergy configurations endemic to Floquet-Majorana detection schemes, we show that stroboscopic heat transport and spin density are robust observables to detect both the dynamical phase transitions and Majorana modes in dissipative settings. We find that the heat current provides very clear signatures of these Floquet topological phase transitions. In particular, we observe that the derivative of the heat current, with respect to a control parameter, changes sign at the boundaries separating topological phases with differing nonzero numbers of Floquet-Majorana modes. We present a simple scheme to directly count the number of Floquet-Majorana modes in a phase from the Fourier transform of the local spin density profile. Our results are valid provided the anisotropies are not strong and can be easily implemented in quantum engineered systems.

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“…So far, CQED has been limited by standard SIS JJs based on aluminum and its oxide to fields <10 mT, the critical field of bulk aluminum [9]. However, interesting applications such as coupling CQED devices to polarized electronspin ensembles serving as quantum memories [10] and using qubits as charge-parity detectors in Majorana based topological quantum computation [11,12] require fields of ∼0.5 T. In such fields, more fundamental effects, such as topological phase transitions [13] and degeneracy lifting of the Andreev bound states which underlie the Josephson effect [14][15][16][17], can be studied. Entering this important regime for CQED requires the use of field-compatible superconductors and nonstandard JJs [18][19][20][21][22].…”

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confidence: 99%