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Visualization of superparamagnetic dynamics in magnetic topological insulators
Ella O Lachman1, Andrea F Young2, Anthony Richardella3
1Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel.
Science Advances
|November 25, 2015
Summary
The quantum anomalous Hall state in magnetic topological insulators exhibits complex dynamics. Magnetic domains, not bulk ferromagnetism, drive phase transitions, revealing a coupled interplay between magnetic and electronic systems.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Phenomena
Background:
- Quantized Hall conductance is observed in 2D electronic systems with broken time reversal symmetry.
- The quantum anomalous Hall state in magnetic topological insulators exhibits this phenomenon without external magnetic fields, attributed to ferromagnetic order.
Purpose of the Study:
- To visualize the dynamics of the quantum phase transition in the quantum anomalous Hall state.
- To investigate the role of magnetic order in the transition between Hall plateaus.
Main Methods:
- Scanning nanoSQUID (nano-superconducting quantum interference device) magnetic imaging.
- Analysis of Cr-doped (Bi,Sb)2Te3 thin films.
Main Results:
- Revealed a superparamagnetic state composed of weakly interacting magnetic domains (few tens of nanometers).
- Observed that magnetic domain reversals drive the electronic Hall plateau transition.
- Discovered that the electronic system can influence the magnetic system's dynamics.
Conclusions:
- The quantum phase transition is driven by dynamics of nanoscale magnetic domains, not bulk ferromagnetism.
- A subtle, coupled interplay exists between the magnetic and electronic systems during the quantum phase transition.
Keywords:
Bi_2Te_3Cr-Bi_2Te_3QAHEQhantum Anomalous Hall EffectSQUIDTopological InsulatorsmagnetismnanoSQUIDsuperparamagneticMore Related Videos
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