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We perform a systematic study of Andreev conversion at the interface between a superconductor and graphene in the quantum Hall (QH) regime. We find that the probability of Andreev conversion from electrons to holes follows an unexpected but clear trend: the dependencies on temperature and magnetic field are nearly decoupled. We discuss these trends and the role of the superconducting vortices, whose normal cores could both absorb and dephase the individual electrons in a QH edge. Our study may pave the road to engineering future generation of hybrid devices for exploiting superconductivity proximity in chiral channels. 

Superconducting diodes areproposed nonreciprocal circuit elements thatshould exhibit nondissipative transport inone direction while being resistive intheopposite direction. Multiple examples ofsuch devices have emerged inthepastcouple ofyears; however, their efficiency istypically limited, andmost ofthem require amagnetic field tofunction. Here wepresent adevice thatachieves efficiencies approaching 100% while operating atzero field. Our samples consist ofanetwork ofthree graphene Josephson junctions linked byacommon superconducting island, towhich werefer asa Josephson triode. Thethree-terminal nature ofthedevice inherently breaks theinversion symmetry, andthecontrol current applied toone ofthecontacts breaks thetime-reversal symmetry. Thetriode’s utility isdemonstrated byrectifying asmall (nA scale amplitude) applied square wave. Wespeculate thatdevices ofthistype could berealistically employed inthemodern quantum circuits. 

Revealing anisotropic nature of 2D superconductivity in the context of electronic structure, orbital character, and spin texture. 

The search for topological excitations such as Majorana fermions has spurred interest in the boundaries between distinct quan- tum states. Here, we explore an interface between two prototypical phases of electrons with conceptually different ground states: the integer quantum Hall insulator and the s-wave superconductor. We find clear signatures of hybridized electron and hole states similar to chiral Majorana fermions, which we refer to as chiral Andreev edge states (CAESs). These propagate along the interface in the direction determined by the magnetic field and their interference can turn an incoming electron into an out- going electron or hole, depending on the phase accumulated by the CAESs along their path. Our results demonstrate that these excitations can propagate and interfere over a significant length, opening future possibilities for their coherent manipulation. 

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.