RESUMEN
Quantum coherent transport of surface states in a mesoscopic nanowire of the three-dimensional topological insulator Bi(2}Se(3) is studied in the weak-disorder limit. At very low temperatures, many harmonics are evidenced in the Fourier transform of Aharonov-Bohm oscillations, revealing the long phase coherence length of spin-chiral Dirac fermions. Remarkably, from their exponential temperature dependence, we infer an unusual 1/T power law for the phase coherence length L(φ)(T). This decoherence is typical for quasiballistic fermions weakly coupled to their environment.
RESUMEN
We investigate the crossed Andreev reflections between two graphene leads connected by a narrow superconductor. When the leads are, respectively, of the n and p type, we find that electron elastic cotunneling and local Andreev reflection are both eliminated even in the absence of any valley-isospin or spin polarizations. We further predict oscillations of both diagonal and cross conductances as a function of the distance between the graphene-superconductor interfaces.
RESUMEN
We demonstrate that in a superconducting multilayered system with alternating interlayer coupling a new type of nonuniform superconducting state can be realized under an in-plane magnetic field. The Zeeman effect in this state is compensated by the energy splitting between bonding and antibonding levels. At low temperature such a compensation mechanism leads to field-induced superconductivity. We discuss the conditions for the experimental observation of the predicted phenomena.