TY  - JOUR
A1  - Sacépé, Benjamin
A1  - Oostinga, Jeroen B.
A1  - Li, Jian
A1  - Ubaldini, Alberto
A1  - Couto, Nuno J. G.
A1  - Giannini, Enrico
A1  - Morpurgo, Alberto F.
T1  - Gate-tuned normal and superconducting transport at the surface of a topological insulator
JF  - Nature Communications
N2  - Three-dimensional topological insulators are characterized by the presence of a bandgap in their bulk and gapless Dirac fermions at their surfaces. New physical phenomena originating from the presence of the Dirac fermions are predicted to occur, and to be experimentally accessible via transport measurements in suitably designed electronic devices. Here we study transport through superconducting junctions fabricated on thin Bi2Se3 single crystals, equipped with a gate electrode. In the presence of perpendicular magnetic field B, sweeping the gate voltage enables us to observe the filling of the Dirac fermion Landau levels, whose character evolves continuously from electron- to hole-like. When B=0, a supercurrent appears, whose magnitude can be gate tuned, and is minimum at the charge neutrality point determined from the Landau level filling. Our results demonstrate how gated nano-electronic devices give control over normal and superconducting transport of Dirac fermions at an individual surface of a three-dimensional topological insulators.
KW  - Physical sciences
KW  - Condensed matter
KW  - Materials science
KW  - nanotechnology
Y1  - 2011
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-140175
VL  - 2
ER  - 
TY  - JOUR
A1  - Oostinga, Jeroen B.
A1  - Maier, Luis
A1  - Schüffelgen, Peter
A1  - Knott, Daniel
A1  - Ames, Christopher
A1  - Brüne, Christoph
A1  - Tkachov, Grigory
A1  - Buhmann, Hartmut
A1  - Molenkamp, Laurens W.
T1  - Josephson Supercurrent through the Topological Surface States of Strained Bulk HgTe
JF  - Physical Review X
N2  - Strained bulk HgTe is a three-dimensional topological insulator, whose surface electrons have a high mobility (~ 30 000 cm\(^2\)=Vs), while its bulk is effectively free of mobile charge carriers. These properties enable a study of transport through its unconventional surface states without being hindered by a parallel bulk conductance. Here, we show transport experiments on HgTe-based Josephson junctions to investigate the appearance of the predicted Majorana states at the interface between a topological insulator and a superconductor. Interestingly, we observe a dissipationless supercurrent flow through the topological surface states of HgTe. The current-voltage characteristics are hysteretic at temperatures below 1 K, with critical supercurrents of several microamperes. Moreover, we observe a magnetic-field-induced Fraunhofer pattern of the critical supercurrent, indicating a dominant \(2\pi\)-periodic Josephson effect in the unconventional surface states. Our results show that strained bulk HgTe is a promising material system to get a better understanding of the Josephson effect in topological surface states, and to search for the manifestation of zero-energy Majorana states in transport experiments.
KW  - topological insulators
KW  - mesoscopics
KW  - superconductivity
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-129834
VL  - 3
IS  - 021007
ER  -