Dresden 2003 – scientific programme

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HL: Halbleiterphysik

HL 26: Transport im hohen Magnetfeld/Quanten-Hall-Effekt

HL 26.7: Talk

Tuesday, March 25, 2003, 16:45–17:00, BEY/154

Andreev reflection in superconductor/2DEG junctions in quantizing magnetic fields — •I.E. Batov^1,2, Th. Schäpers¹, J. Knobbe¹, and A.V. Ustinov² — ¹Institut für Schichten und Grenzflächen, Forschungszentrum Jülich, 52425 Jülich, Germany — ²Physikalisches Institut III, Universität Erlangen–Nürnberg, Erwin–Rommel–Str. 1, 91058 Erlangen, Germany

The study of hybrid systems consisting of superconductors (S) in contact with a two-dimensional electron gas (2DEG) has attracted considerable interest in recent years. By taking Andreev reflection into account, magnetoconductance oscillations have been predicted in the limit of quantizing magnetic fields [1]. In this work, we have experimentally studied the differential magnetoconductance of S/2DEG/S and S/2DEG/normal metal junctions formed by superconducting NbN electrodes and the 2DEG in a high-mobility InGaAs/InP heterostructure. The differential conductance of the S/2DEG/S and S/2DEG/N junctions measured at zero magnetic field revealed features characteristic for Andreev reflection at the interface. These features remain at high magnetic fields. We observed conductance oscillations as a function of magnetic field at zero dc bias current in S/2DEG/S and S/2DEG/N junctions. At high dc bias currents, quantum Hall steps appear in the magnetic field dependence of the differential conductance. Experimental results obtained can be qualitatively explained by taking Andreev reflection in high magnetic fields into consideration [1].

[1] Hoppe et al.,PRL, v.84, 1804 (2000)