Quantum Hall–based superconducting interference device

Abstract

We present a study of a graphene-based Josephson junction with dedicated side gates carved from the same sheet of graphene as the junction itself. These side gates are highly efficient and allow us to modulate carrier density along either edge of the junction in a wide range. In particular, in magnetic fields in the 1- to 2-T range, we are able to populate the next Landau level, resulting in Hall plateaus with conductance that differs from the bulk filling factor. When counter-propagating quantum Hall edge states are introduced along either edge, we observe a supercurrent localized along that edge of the junction. Here, we study these supercurrents as a function of magnetic field and carrier density.

Majorana fermions on the quantum Hall edge

“…It is worth pointing out that our single-channel results also apply to the case of a Hall bar made of graphene [4,8,9], provided only the lowest Landau level is occupied and the Fermi energy is larger than the superconducting gap so the Dirac point physics [36] is not involved. We have also checked that the addition of a small Zeeman term to the Hall bar Hamiltonian does not affect the Fraunhofer patterns provided the Landau levels of both spins are occupied and the Zeeman splitting is much smaller than the level spacing δε, as assumed throughout the present work.…”

“…What might have been seen as a bold question has now become a concrete and tangible possibility [2]. Experimental groups have recently managed to make sufficiently transparent contacts between superconductors and quantum Hall states [3][4][5][6], not only enabling the measurement of a supercurrent [4,7,8], but also establishing the existence of the so called chiral Andreev edge state [9], a one-way hybrid electron-hole mode that propagates along these interfaces [10]. The electron-hole cyclotron orbits in the semiclassical regime were also recently imaged in a focusing experiment [11].…”

Flavoured quantum Hall phase in graphene/CrOCl heterostructures

“…Quantum Hall effect (QHE), the ground to construct modern conceptual electronic systems with emerging physics [1][2][3][4][5], is often much influenced by the interplay between the host twodimensional electron gases and the substrate, sometimes predicted to exhibit exotic topological states [6,7]. Yet the understanding of the underlying physics and the controllable engineering of this paradigm of interaction remain challenging.…”

Quantized conductance with nonzero shot noise as a signature of Andreev edge state

“…The realization of electron-hole hybrid states called Andreev edge states (AESs) [12,13] at the QH-SC interface is an important step in this quest and graphene hosting clean QH edge states at a moderate magnetic field is an ideal platform. The recent developments of several superconductors with a large critical magnetic field and transparent interfaces with high quality graphene have paved the way for a number of interesting experimental observations [14][15][16][17][18][19][20][21][22][23][24][25][26], such as crossed Andreev conversion [18], supercurrents in the QH regime [16], inter-Landau-level Andreev reflection [19], and interference of chiral AESs [21]. Despite this progress, the identification of AESs remains scarce, and its dynamics have remained unexplored in the presence of disorder and dissipation.…”