Superparamagnetism-induced Mesoscopic Electron Focusing in Topological Insulators
ORAL
Abstract
Breaking time-reversal symmetry by the presence of magnetic dopants re-opens the backscattering channel in the surface state of strong topological insulators. Recent quasiparticle interference measurements at the surface of Mn-doped Bi2Te3 at 4K reveal directionally focused and undamped interference patterns [1].
By means of ab-initio calculations we reveal that the measured mesoscopic coherence relies on two conditions: (i) a hexagonal Fermi surface with large parallel segments (nesting) and (ii) magnetic dopants, which couple to a high-spin superparamagnetic state.
Our theory is supported by x-ray magnetic circular dichroism experiments showing superparamagnetism even at very dilute Mn concentrations, which is a result of Dirac-fermion-mediated RKKY interactions [1,2]. Thus, our findings demonstrate how spin information can be transmitted over long distances, allowing the design of experiments based on coherent quantum effects in topological insulators.
[1] P. Sessi, P. Rüßmann et al., PRB 94, 075137 (2016)
[2] A. Barla, P. Rüßmann et al., in preparation
By means of ab-initio calculations we reveal that the measured mesoscopic coherence relies on two conditions: (i) a hexagonal Fermi surface with large parallel segments (nesting) and (ii) magnetic dopants, which couple to a high-spin superparamagnetic state.
Our theory is supported by x-ray magnetic circular dichroism experiments showing superparamagnetism even at very dilute Mn concentrations, which is a result of Dirac-fermion-mediated RKKY interactions [1,2]. Thus, our findings demonstrate how spin information can be transmitted over long distances, allowing the design of experiments based on coherent quantum effects in topological insulators.
[1] P. Sessi, P. Rüßmann et al., PRB 94, 075137 (2016)
[2] A. Barla, P. Rüßmann et al., in preparation
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Presenters
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Philipp Rüßmann
PGI-1, Forschungszentrum Jülich
Authors
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Philipp Rüßmann
PGI-1, Forschungszentrum Jülich
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Phivos Mavropoulos
PGI-1, Forschungszentrum Jülich
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Stefan Bluegel
Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich, Peter Grünberg Institut, Forschungszentrum Jülich, Peter Grünberg Institut (PGI) and Institute for Advanced Simulation (IAS), Forschungszentrum Jülich and JARA, PGI-1, Forschungszentrum Jülich, Forschungszentrum Julich GmbH, PGI-1, FZ Juelich