RESUMEN
We report experimental investigations of transport through bilayer graphene (BLG)/chromium trihalide (CrX3; X = Cl, Br, I) van der Waals interfaces. In all cases, a large charge transfer from BLG to CrX3 takes place (reaching densities in excess of 1013 cm-2), and generates an electric field perpendicular to the interface that opens a band gap in BLG. We determine the gap from the activation energy of the conductivity and find excellent agreement with the latest theory accounting for the contribution of the σ bands to the BLG dielectric susceptibility. We further show that for BLG/CrCl3 and BLG/CrBr3 the band gap can be extracted from the gate voltage dependence of the low-temperature conductivity, and use this finding to refine the gap dependence on the magnetic field. Our results allow a quantitative comparison of the electronic properties of BLG with theoretical predictions and indicate that electrons occupying the CrX3 conduction band are correlated.
RESUMEN
We perform magnetotransport experiments on VI3 multilayers to investigate the relation between ferromagnetism in bulk and in exfoliated layers. The magnetoconductance measured on field-effect transistors and tunnel barriers shows that the Curie temperature of exfoliated multilayers is TC = 57 K, larger than in bulk (TC,bulk = 50 K). Below T ≈ 40 K, we observe an unusual evolution of the tunneling magnetoconductance, analogous to the phenomenology observed in bulk. Comparing the magnetoconductance measured for fields applied in- or out-of-plane corroborates the analogy, allows us to determine that the orientation of the easy-axis in multilayers is similar to that in bulk, and suggests that the in-plane component of the magnetization points in different directions in different layers. Besides establishing that the magnetic state of bulk and multilayers are similar, our experiments illustrate the complementarity of magnetotransport and magneto-optical measurements to probe magnetism in 2D materials.
RESUMEN
Suspended Bernal-stacked graphene multilayers up to an unexpectedly large thickness exhibit a broken-symmetry ground state whose origin remains to be understood. We show that a finite-temperature second-order phase transition occurs in multilayers whose critical temperature (T c) increases from 12 kelvins (K) in bilayers to 100 K in heptalayers. A comparison of the data with a phenomenological model inspired by a mean-field approach suggests that the transition is associated with the appearance of a self-consistent valley- and spin-dependent staggered potential that changes sign from one layer to the next, appearing at T c and increasing upon cooling. The systematic evolution with thickness of several measured quantities imposes constraints on any microscopic theory aiming to analyze the nature of electronic correlations in this system.
