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Exchange-coupling-induced symmetry breaking in topological insulators
Peng Wei1, Ferhat Katmis, Badih A Assaf
1Francis Bitter Magnet Lab, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. pwei@mit.edu
Physical Review Letters
|May 21, 2013
Summary
We induced ferromagnetism in topological insulators (TI) using EuS, creating an exchange gap necessary for exotic phenomena like Majorana fermions. This defect-free method advances TI research.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Phenomena
Background:
- Topological insulators (TI) possess unique surface states with potential for novel quantum effects.
- An exchange gap in these surface states is crucial for observing phenomena like the topological magnetoelectric effect and confining Majorana fermions.
- Previous methods for creating this gap often introduced defects, hindering TI properties.
Purpose of the Study:
- To experimentally demonstrate proximity-induced ferromagnetism in a topological insulator (TI) without introducing defects.
- To create an exchange gap in the Dirac surface states of a TI.
- To pave the way for observing unique TI properties and applications.
Main Methods:
- Epitaxial growth of a ferromagnetic insulator (EuS) layer on a topological insulator (Bi2Se3).
- Characterization using magnetic measurements.
- Investigation of transport properties via anomalous Hall effect and magnetoresistance measurements.
Main Results:
- Successful induction of ferromagnetism in Bi2Se3 via proximity effect with EuS.
- Demonstration of a defect-free interface between the ferromagnetic insulator and the TI.
- Observation of magnetic and magnetotransport signatures indicating the ferromagnetic phase.
Conclusions:
- Proximity-induced ferromagnetism in TIs is achievable without defects using the EuS/Bi2Se3 heterostructure.
- This approach provides a viable route to engineer the exchange gap in TI surface states.
- The findings represent a significant step towards harnessing the exotic properties of topological insulators.
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