What are topological insulators good for? – Yong P. Chen, Purdue

Topological insulators (TI) have recently attracted a lot of interests in both solid state physics and nanoelectronics community. These materials are semiconductors (band insulators) in the bulk (with “negative bandgap”), but have “topologically protected” conducting surfaces with spin-polarized, graphene-like Dirac electrons, promising a large number of exotic electronic and optical properties. But what are these materials really good for, and what may be some of the first practical device applications of topological insulators? In this talk, I will review the key electronic properties and device potentials of TIs. I will present our recent experimental demonstration of the most intrinsic TI so far (with no measureable bulk conduction – realizing a 3D material whose conductance does not depend on thickness and comes only from its surface, some even at room temperature), along with some of the most salient electronic transport signatures of TI’s spin-helical, Dirac fermion “topological surface states”, such as the “half-integer quantum Hall effect”, and the “spin-momentum locking” detected by direct electrical injection and detection of spin-polarized surface current.  I will discuss some examples of potential devices applications of TIs in spintronics and energy conversion (eg. thermoelectrics).

 

References:

1. Yong P. Chen, Proc. SPIE 8373, 83730B (2012)
2. Y. Xu et al., Nature Physics 10, 956 (2014); Y. Xu et al., arXiv:1511.04597 (2015)
3. J. Tian et al. Solid State Communications 191, 1 (2014); J.Tian et al., Scientific Reports 5, 14293 (2015)
4. L. A. Jauregui et al., Scientific Reports 5, 8452 (2015); L. A. Jauregui et al., Nature Nanotechnology, in press, arxiv:1503.00685 (2015)