Datensatz

Zusammenfassung

We introduce Andreev scattering (electron-hole conversion at all interface of a normal conductor to a superconductor) at the outer vertices of a quantum star graph and examine its effect on the spectrum. More specifically we show that the density of states in Andreev graphs is suppressed near the Fermi energy where a spectral gap may occur. The size and existence of such a gap depends on one side oil the Andreev scattering amplitudes and, oil the other side, on the properties of the electron-electron scattering matrix at the central vertex. We also show that the bond length fluctuations have a minor effect oil the spectrum near the Fermi energy.