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Recent experiments on magic-angle twisted bilayer graphene have shown the formation of flat bands, suggesting that electronic correlation effects are likely to dominate in this material. However, a global transport measurement showing distinct signatures of strong correlations—such as local moments arising from the flat bands—is missing. Here we demonstrate the presence of emergent local moments through their impact on entropy extracted from thermopower measurements. In addition to sign changes in the thermopower at the Dirac point and full filling of the flat bands, we observe sign changes near the quarter-filled bands that do not vary with temperature from 5 K to 60 K. This is in contrast to temperature-dependent crossing points seen in our study on twisted bilayer graphene devices with weaker correlations. Furthermore, we find that applying a magnetic field reduces the thermopower, consistent with spin entropy suppression observed in layered oxides under partial spin polarization. Neither the robust crossing points nor the suppression by a magnetic field can be explained solely from the contributions of band fermions; instead, our data suggest a dominant contribution coming from the entropy of the emergent localized moments of a strongly correlated flat band. 

Quasicrystals are characterized by atomic arrangements possessing long-range order without periodicity. Van der Waals (vdW) bilayers provide a unique opportunity to controllably vary atomic alignment between two layers from a periodic moir´e crystal to an aperiodic quasicrystal. Here, we reveal a remarkable consequence of the unique atomic arrangement in a dodecagonal WSe2 quasicrystal: the K and Q valleys in separate layers are brought arbitrarily close in momentum space via higher-order Umklapp scatterings. A modest perpendicular electric field is sufficient to induce strong interlayer K − Q hybridization, manifested as a new hybrid excitonic doublet. Concurrently, we observe the disappearance of the trion resonance and attribute it to quasicrystal potential driven localization. Our findings highlight the remarkable attribute of incommensurate systems to bring any pair of momenta into close proximity, thereby introducing a novel aspect to valley engineering. 

Abstract The electron antineutrino flux limits are presented for the brightest gamma-ray burst (GRB) of all time, GRB221009A, over a range of 1.8–200 MeV using the Kamioka Liquid Scintillator Antineutrino Detector. Using multiple time windows ranging from minutes to days surrounding the event to search for electron antineutrinos coincident with the GRB, we set an upper limit on the flux under the assumption of several power-law neutrino source spectra, with power-law indices ranging from 1.5 to 3 in steps of 0.5. No excess was observed in any time windows ranging from seconds to days around the event trigger timeT₀. For a power-law index of 2 and a time window ofT₀ ±  500 s, a flux upper limit of 2.34  ×  10⁹cm⁻²was calculated. The limits are compared to the results presented by IceCube. 

Abstract We revisit and extend the standard bosonic interpretation of interlayer excitons (ILX) in the moiré potential of twisted heterostructures of transition-metal dichalcogenides. In our experiments, we probe a high quality MoSe 2 /WSe 2 van der Waals bilayer heterostructure via density-dependent photoluminescence spectroscopy and reveal strongly developed, unconventional spectral shifts of the emergent moiré exciton resonances. The observation of saturating blueshifts of successive exciton resonances allow us to explain their physics in terms of a model utilizing fermionic saturable absorbers. This approach is strongly inspired by established quantum-dot models, which underlines the close analogy of ILX trapped in pockets of the moiré potential, and quantum emitters with discrete eigenstates.