Ballistic Graphene Cooper Pair Splitter

Abstract

We report an experimental study of a Cooper pair splitter based on ballistic graphene multiterminal junctions. In a two transverse junction geometry, namely the superconductor-graphene-superconductor and the normal metal-graphene-normal metal, we observe clear signatures of Cooper pair splitting in the local as well as nonlocal electronic transport measurements. Our experimental data can be very well described by our beam splitter model. These results open up possibilities to design new entangled state detection experiments using ballistic Cooper pair splitters.

Electrical and thermal transport in a twisted heterostructure of transition metal dichalcogenide and CrI$_3$ connected to a superconductor

“…Owing to the interplay of superconductivity and the unique electronic structure of atomically thin two-dimensional (2D) materials, superconducting heterostructures based on 2D materials have received considerable attention in quantum transport, and application of superconducting nanoelectronics [26][27][28][29][30][31][32][33][34][35][36][37][38][39]. Many theoretical and experimental works have found peculiar AR processes at low energies [26][27][28][29][30][31][32] and nonlocal processes have been predicted to occur under various conditions [30,31,[33][34][35][36][37].…”

“…Many theoretical and experimental works have found peculiar AR processes at low energies [26][27][28][29][30][31][32] and nonlocal processes have been predicted to occur under various conditions [30,31,[33][34][35][36][37]. In particular, Cooper pair splitting has been observed in graphene [38]. To be specific, interband specular AR has been demonstrated to appear in graphene-based superconducting hybrid structures [26,[30][31][32] as well as the intraband specular AR in thin films of topological insulators [27,28], which are absent in ordinary metal-superconductor interfaces.…”

Real-time observation of Cooper pair splitting showing strong non-local correlations

“…Until now, the splitting of Cooper pairs has been indirectly inferred from measurements of the currents in the outputs of a Cooper pair splitter 6 – 26 or their low-frequency cross-correlations 12 , 15 . These approaches rely on measuring the average currents, or small fluctuations around them, due to a large number of splitting events.…”

Dynamic Cooper Pair Splitter

“…By splitting the Cooper pairs in a superconductor into different normal-state leads, spin entanglement between spatially separated electrons can be achieved [2,3]. Cooper pair splitters have been realized in several types of solid-state architectures [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], for instance, using quantum dots [6,9,11], carbon nanotubes [7], or graphene [15,16,18,19]. Experimentally, the splitting process has been observed by measuring the nonlocal conductance or the noise [8,12] and recently using singleelectron detectors [20].…”

“…While experiments so far have mainly focused on dynamic sources that emit a single electron per cycle, theoretical works have explored the dynamic generation of more complex quantum states of entangled electrons in normal metals [31][32][33][34]. On the other hand, the concept of controlling the splitting of Cooper pairs with timedependent driving fields has not been considered before; however, given the very recent experimental progress in the field [18][19][20], such ideas are finally within reach. In this Letter, we propose and analyze a dynamic Cooper pair splitter that can deliver a noiseless and regular stream of spin-entangled electrons.…”