Topological crystalline insulators
We are currently investigating new states of matter that arise in topological crystalline insulator due their unique valley degenerate topological properties. We can synthesize high mobility epilayers of PbSnSe to observe quantum coherent phenomena and quantum oscillations in magnetooptics and magnetotransport. Our goal is to study multivalley quantized Hall phenomena in these materials. See: arxiv2010.02294.
Magnetism in topological crystalline insulators
We are studying two types of induced magnetism in topological crystalline insulators: bulk doping and proximity magnetism. We expect to reveal the intrinsic anomalous Hall effect resulting from the Berry phase of Dirac states in magnetic PbSnSe as well as a new phase of matter where the spin, valley and topological index are coupled. Magnetic topological crystalline superlattices can also be used to generate new quasiparticles such Weyl fermions and nodal line states.
Magnetism in the Bi2Te3 system
The Bi2Te3-Sb2Te3 system hosts the quantum anomalous Hall effect. Introducing Mn in Bi2Te3 can yield a self-assembled MnBi2Te4-MnBi2Te3 superlattice. This superlattice hosts a quantum anomalous Hall effect at elevated temperatures. We are currently working on the MBE synthesis of such superlattices to study their potential to achieve a spontaneous quantum anomalous Hall effect.
Magnetic III-V materials
The magnetism in III-Mn-V materials is mediated by mobile charge carriers that result in a finite exchange interaction between Mn atoms. The origin of anomalous Hall effect in these materials is however still debated. We are examining this specific question in the context of recent theories linking strong anomalous Hall effects to the Berry curvature of the band structure.
Our method consists in a hybrid approach that combines material synthesis using MBE and CVD with electrical and optical characterization techniques. It allows us to produce, measure and identify materials with specific electronic and optical properties that can be integrated into functional devices. A list of the synthesis and characterization techniques used in our lab is given below:
- Molecular beam epitaxy (with the MBE group at Notre Dame)
- Chemical vapor deposition
- Infrared magnetooptical spectroscopy
- Strong magnetic fields