Unconventional superconductivity in magic-angle graphene superlattices. Evidence of a gate-tunable Mott insulator in a trilayer graphene moiré superlattice. Correlated insulator behaviour at half-filling in magic-angle graphene superlattices. Cloning of Dirac fermions in graphene superlattices. Massive Dirac fermions and Hofstadter butterfly in a van der Waals heterostructure. Hofstadter’s butterfly and the fractal quantum Hall effect in moiré superlattices. This work presents opportunities to control two-dimensional moiré optics through variation of the twist angle.ĭean, C. Together with a characteristic dependence on power and excitation energy, these results suggest that the origin of the observed effects is interlayer excitons trapped in a smooth moiré potential with inherited valley-contrasting physics. The emitters exhibit strong circular polarization of the same helicity for a given twist angle, which suggests that the trapping potential retains three-fold rotational symmetry. This is consistent with the umklapp recombination of interlayer excitons near the commensurate 21.8-degree twist angle 7. At twist angles of approximately 20 degrees the emitters become two orders of magnitude dimmer however, they possess the same g-factor as the heterobilayer at a twist angle of approximately 60 degrees. The g-factors match those of the free interlayer exciton, which is determined by one of two possible valley-pairing configurations. The emitter g-factors are homogeneous across the same sample and take only two values, −15.9 and 6.7, in samples with approximate twist angles of 60 degrees and 0 degrees, respectively. At low temperatures, we observe photoluminescence close to the free interlayer exciton energy but with linewidths over one hundred times narrower (around 100 microelectronvolts). Here we report experimental evidence of interlayer valley excitons trapped in a moiré potential in molybdenum diselenide (MoSe 2)/tungsten diselenide (WSe 2) heterobilayers. In addition, theory predicts that notable effects on optical excitations could result from a moiré potential in two-dimensional valley semiconductors 7, 8, 9, but these signatures have not been detected experimentally. This approach has led to electronic phenomena including the fractal quantum Hall effect 1, 2, 3, tunable Mott insulators 4, 5 and unconventional superconductivity 6. In two-dimensional materials, a moiré pattern with a superlattice potential can be formed by vertically stacking two layered materials with a twist and/or a difference in lattice constant. The formation of moiré patterns in crystalline solids can be used to manipulate their electronic properties, which are fundamentally influenced by periodic potential landscapes.
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