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Unconventional superconductivity in magic-angle graphene superlattices
The realization of intrinsic unconventional superconductivity is reported—which cannot be explained by weak electron–phonon interactions—in a two-dimensional superlattice created by stacking two sheets of graphene that are twisted relative to each other by a small angle.
Layer-dependent ferromagnetism in a van der Waals crystal down to the monolayer limit
Since the discovery of graphene, the family of two-dimensional materials has grown, displaying a broad range of electronic properties. Recent additions include semiconductors with spin–valley
Correlated insulator behaviour at half-filling in magic-angle graphene superlattices
It is shown experimentally that when this angle is close to the ‘magic’ angle the electronic band structure near zero Fermi energy becomes flat, owing to strong interlayer coupling, and these flat bands exhibit insulating states at half-filling, which are not expected in the absence of correlations between electrons.
Scanning tunnelling microscopy and spectroscopy of ultra-flat graphene on hexagonal boron nitride.
Scanning tunnelling microscopy is used to show that graphene conforms to hBN, as evidenced by the presence of Moiré patterns, but contrary to predictions, this conformation does not lead to a sizeable band gap because of the misalignment of the lattices.
Control over topological insulator photocurrents with light polarization.
It is shown that illuminating the topological insulator Bi(2)Se(3) with circularly polarized light generates a photocurrent that originates from topological helical Dirac fermions, and that reversing the helicity of the light reverses the direction of the photocurrent.
Emergence of superlattice Dirac points in graphene on hexagonal boron nitride
It is well known that graphene deposited on hexagonal boron nitride produces moire patterns in scanning tunnelling microscopy images. The interaction that produces this pattern also produces a
Observation of Floquet-Bloch States on the Surface of a Topological Insulator
Using time- and angle-resolved photoemission spectroscopy, it is shown that an intense ultrashort midinfrared pulse with energy below the bulk band gap hybridizes with the surface Dirac fermions of a topological insulator to form Floquet-Bloch bands.
Bipolar supercurrent in graphene
Light is shed on the special role of time reversal symmetry in graphene, and phase coherent electronic transport at the Dirac point is demonstrated, finding that not only the normal state conductance of graphene is finite, but also a finite supercurrent can flow at zero charge density.
Hot Carrier–Assisted Intrinsic Photoresponse in Graphene
The intrinsic optoelectronic response of high-quality dual-gated monolayer and bilayer graphene p-n junction devices is reported, providing strong evidence that nonlocal hot carrier transport, rather than the photovoltaic effect, dominates the intrinsic photoresponse in graphene.
Tunable Phonon Polaritons in Atomically Thin van der Waals Crystals of Boron Nitride
The measured dispersion of polaritonic waves was shown to be governed by the crystal thickness according to a scaling law that persists down to a few atomic layers, likely to hold true in other polar van der Waals crystals and may lead to new functionalities.