We report a study of one-dimensional subband splitting in a bilayer graphene quantum point contact in which quantized conductance in steps of 4 e 2 /h is clearly defined down to the lowest subband. While our source-drain bias spectroscopy measurements reveal an unconventional confinement, we observe a full lifting of the valley degeneracy at high magnetic fields perpendicular to the bilayer graphene plane for the first two lowest subbands where confinement and Coulomb interactions are the strongest and a peculiar merging/mixing of K and K valleys from two non-adjacent subbands with indices (N, N + 2) which are well described by our semi-phenomenological model. arXiv:1809.02458v2 [cond-mat.mes-hall]
We present experimental results and a theoretical model for the gate-controlled spin-valve effect in carbon nanotubes with side-attached single-molecule magnets TbPc (Terbium(III) bis-phthalocyanine). These structures show a giant magnetoresistance up to 1000% in experiments on single-wall nanotubes that are tunnel-coupled to the leads. The proposed theoretical model combines the spin-dependent Fano effect with Coulomb blockade and predicts a spin-spin interaction between the TbPc molecules, mediated by conducting electrons via the charging effect. This gate-tuned interaction is responsible for the stable magnetic ordering of the inner spins of the molecules in the absence of magnetic field. In the case of antiferromagnetic arrangement, electrons with either spin experience the scattering by the molecules, which results in blocking the linear transport. In strong magnetic fields, the Zeeman energy exceeds the effective antiferromagnetic coupling and one species of electrons is not scattered by molecules, which leads to a much lower total resistance at the resonant values of gate voltage, and hence to a supramolecular spin-valve effect.
We present a non-perturbative calculation of indirect exchange interaction
between two paramagnetic impurities via 2D free carriers gas separated by a
tunnel barrier. The new method accounts for the impurity attractive potential
producing a bound state. The calculations show that for if the bound impurity
state energy lies within the energy range occupied by the free 2D carriers the
indirect exchange interaction is strongly enhanced due to resonant tunneling
and exceeds by a few orders of magnitude what one would expect from the
conventional RKKY approach.Comment: 4 pages, 2 figure
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.