Key Points
- Researchers discovered a hidden band gap in MnBi₂Te₄ using circularly polarized light.
- The study confirms the breaking of time-reversal symmetry in the material.
- Floquet-Bloch manipulation was crucial in revealing the previously undetected gap.
- Magnetic defects influence the gap asymmetry observed in the material.
Researchers at the University of Illinois have made a significant breakthrough in studying magnetic topological insulators (TIs) by using circularly polarized light to uncover a hidden band gap in manganese bismuth telluride (MnBi₂Te₄). This discovery, published in Nature Physics, resolves a long-standing debate about the presence of a band gap in the material and marks a milestone in the engineering of novel quantum states using light.
Unlike non-magnetic TIs, which obey time-reversal symmetry (TRS) and conduct electricity on their surfaces while insulating their interiors, magnetic TIs break this symmetry. This leads to unique quantum phenomena such as the quantum anomalous Hall effect (QAHE). This effect allows for energy-efficient electronics without external magnetic fields, making magnetic TIs promising for quantum computing applications.
MnBi₂Te₄, an intrinsic magnetic TI, has been the focus of recent research due to its naturally occurring magnetism. However, conflicting experimental results have left the existence of a band gap uncertain. Using angle-resolved photoemission spectroscopy (ARPES), researchers initially found no gap, prompting them to explore alternative methods.
The team employed Floquet-Bloch manipulation by exposing MnBi₂Te₄ to the right- and left-circularly polarized (RCP and LCP) light. They discovered that RCP light created a band gap nearly twice the size created by LCP light in the low-temperature phase, confirming the breaking of TRS and the presence of an asymmetrical gap.
This finding paves the way for further exploration of Floquet-Bloch manipulation in other magnetic TIs, which could potentially have applications in energy-efficient devices and robust quantum computing technologies. The study also highlights the role of magnetic defects in influencing material properties and calls for additional research into electrical conductivity and quantum Hall effects.