TY  - JOUR
A1  - König, Markus
A1  - Baenninger, Matthias
A1  - Garcia, Andrei G. F.
A1  - Harjee, Nahid
A1  - Pruitt, Beth L.
A1  - Ames, C.
A1  - Leubner, Philipp
A1  - Brüne, Christoph
A1  - Buhmann, Hartmut
A1  - Molenkamp, Laurens W.
A1  - Goldhaber-Gordon, David
T1  - Spatially Resolved Study of Backscattering in the Quantum Spin Hall State
JF  - Physical Review X
N2  - The discovery of the quantum spin Hall (QSH) state, and topological insulators in general, has sparked strong experimental efforts. Transport studies of the quantum spin Hall state have confirmed the presence of edge states, showed ballistic edge transport in micron-sized samples, and demonstrated the spin polarization of the helical edge states. While these experiments have confirmed the broad theoretical model, the properties of the QSH edge states have not yet been investigated on a local scale. Using scanning gate microscopy to perturb the QSH edge states on a submicron scale, we identify well-localized scattering sites which likely limit the expected nondissipative transport in the helical edge channels. In the micron-sized regions between the scattering sites, the edge states appear to propagate unperturbed, as expected for an ideal QSH system, and are found to be robust against weak induced potential fluctuations.
KW  - mesoscopics
KW  - topological insulators
KW  - transport
KW  - charge
KW  - wells
KW  - branched flow
KW  - nanostructures
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-127225
SN  - 2160-3308
VL  - 3
IS  - 2
ER  - 
TY  - JOUR
A1  - Ma, Eric Yue
A1  - Calvo, M. Reyes
A1  - Wang, Jing
A1  - Lian, Biao
A1  - Mühlbauer, Mathias
A1  - Brüne, Christoph
A1  - Cui, Yong-Tao
A1  - Lai, Keji
A1  - Kundhikanjana, Worasom
A1  - Yang, Yongliang
A1  - Baenninger, Matthias
A1  - König, Markus
A1  - Ames, Christopher
A1  - Buhmann, Hartmut
A1  - Leubner, Philipp
A1  - Molenkamp, Laurens W.
A1  - Zhang, Shou-Cheng
A1  - Goldhaber-Gordon, David
A1  - Kelly, Michael A.
A1  - Shen, Zhi-Xun
T1  - Unexpected edge conduction in mercury telluride quantum wells under broken time-reversal symmetry
JF  - Nature Communications
N2  - The realization of quantum spin Hall effect in HgTe quantum wells is considered a milestone in the discovery of topological insulators. Quantum spin Hall states are predicted to allow current flow at the edges of an insulating bulk, as demonstrated in various experiments. A key prediction yet to be experimentally verified is the breakdown of the edge conduction under broken time-reversal symmetry. Here we first establish a systematic framework for the magnetic field dependence of electrostatically gated quantum spin Hall devices. We then study edge conduction of an inverted quantum well device under broken time-reversal symmetry using microwave impedance microscopy, and compare our findings to a noninverted device. At zero magnetic field, only the inverted device shows clear edge conduction in its local conductivity profile, consistent with theory. Surprisingly, the edge conduction persists up to 9 T with little change. This indicates physics beyond simple quantum spin Hall model, including material-specific properties and possibly many-body effects.
KW  - topological insulators
KW  - surface states
KW  - HgTe
KW  - Hg1-xCdxTe
KW  - vacancies
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-143185
VL  - 6
IS  - 7252
ER  -