Amazing stuff! It's the magic graphene again!
"Magnets and superconductors go together like oil and water — or so scientists have thought. ...
In a paper ... the physicists report that they have discovered a “chiral superconductor” — a material that conducts electricity without resistance, and also, paradoxically, is intrinsically magnetic. ... this exotic superconductivity in ... graphite, the primary material in pencil lead. ...
when four or five sheets of graphene are stacked in this “rhombohedral” configuration, the resulting structure can exhibit exceptional electronic properties that are not seen in graphite as a whole. ..."
From the abstract:
"Chiral superconductors are unconventional superconducting states that break time reversal symmetry spontaneously and typically feature Cooper pairing at non-zero angular momentum. Such states may host Majorana fermions and provide an important platform for topological physics research and fault-tolerant quantum computing. Despite intensive search and prolonged studies of several candidate systems, chiral superconductivity has remained elusive so far.
Here we report the discovery of robust unconventional superconductivity in rhombohedral tetra- and penta-layer graphene without moiré superlattice effects. We observed two superconducting states in the gate-induced flat conduction bands with Tc up to 300 mK and charge density ne down to 2.4*1011 cm-2 in five devices.
Spontaneous time-reversal-symmetry-breaking due to electron’s orbital motion is found, and several observations indicate the chiral nature of these superconducting states, including:
1. In the superconducting state, Rxx shows magnetic hysteresis in varying out-of-plane magnetic field B⊥—absent from all other superconductors;
2. the superconducting states are robust against in-plane magnetic field and are developed within a spin- and valley-polarized quarter-metal phase;
3. the normal states show anomalous Hall signals at zero magnetic field and magnetic hysteresis.
We also observed a critical B⊥ of 1.4 Tesla, higher than any graphene superconductivity and indicates a strong-coupling superconductivity close to the BCS-BEC crossover. Our observations establish a pure carbon material for the study of topological superconductivity, with the promise to explore Majorana modes and topological quantum computing."
Signatures of chiral superconductivity in rhombohedral graphene (no public access)
Signatures of Chiral Superconductivity in Rhombohedral Graphene (preprint, open access)
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