Large magnetic gap at the Dirac point in Bi2Te3/MnBi2Te4 heterostructures
Sprache des Titels:
Englisch
Original Kurzfassung:
(QAHE), which provides quantized edge states for lossless charge-transport
applications1?8. The edge states are hosted by a magnetic energy gap at the Dirac
point2, but hitherto all attempts to observe this gap directly have been unsuccessful.
Observing the gap is considered to be essential to overcoming the limitations of the
QAHE, which so far occurs only at temperatures that are one to two orders of
magnitude below the ferromagnetic Curie temperature, TC (ref. 8). Here we use lowtemperature
photoelectron spectroscopy to unambiguously reveal the magnetic gap
of Mn-doped Bi2Te3, which displays ferromagnetic out-of-plane spin texture and
opens up only below TC. Surprisingly, our analysis reveals large gap sizes at 1 kelvin of
up to 90 millielectronvolts, which is five times larger than theoretically predicted9.
Using multiscale analysis we show that this enhancement is due to a remarkable
structure modification induced by Mn doping: instead of a disordered impurity
system, a self-organized alternating sequence of MnBi2Te4 septuple and Bi2Te3
quintuple layers is formed. This enhances the wavefunction overlap and size of the
magnetic gap10. Mn-doped Bi2Se3 (ref. 11) and Mn-doped Sb2Te3 form similar
heterostructures, but for Bi2Se3 only a nonmagnetic gap is formed and the
magnetization is in the surface plane. This is explained by the smaller spin?orbit
interaction by comparison with Mn-doped Bi2Te3. Our findings provide insights that
will be crucial in pushing lossless transport in topological insulators towards roomtemperature
applications.
Forschungs-