Abstract：We are always searching for new ways to manipulate and engineer materials. To change the properties of a crystal, we can use strategies like chemical doping, applying pressure, changing the temperature or varying the thickness of a film. We also have clever ways to engineer band structures from the ground up in cold-atom optical lattices or photonic crystals. In this talk, I will demonstrate a new scheme to engineer band structures, using topological insulators. We use molecular beam epitaxy (MBE) to stack thin films of trivial and topological insulators in an alternating pattern to form a multilayer heterostructure. Each interface hosts topological interface states. By making each layer < 7nm thick, we allow quantum tunneling between nearby interfaces. In this way, we form an emergent, tunable superlattice band structure where each interface acts as a lattice site and each topological interface state acts as an atomic orbital. After introducing the basic concept, I will present data from angle-resolved photoemission spectroscopy (ARPES) demonstrating an emergent electronic band structure. I will also discuss how we might use this scheme to realize novel topological invariants in both 3D and 1D, as well as other neat applications.
Reference: Belopolski et al., Sci. Adv., e1501692 (2017).

CV : Ilya Belopolski is a graduate student at Princeton University in NJ, USA working with Prof. M. Zahid Hasan using ARPES to study topological phases of matter.

Selected Publications:

1. Ilya Belopolski, et al. A novel condensed matter lattice and a new platform for onedimensional topological phases. Sci. Adv. 3, e1501692 (2017, to appear 24 March).

2. Ilya Belopolski, et al. Discovery of a new type of topological Weyl fermion semimetal state in MoxW1-xTe2. Nat. Commun. 7, 13643 (2016).

3. Ilya Belopolski, et al. A minimal, “hydrogen atom” version of an inversion-breaking Weyl semimetal. Submitted to Nat. Commun. (2017) & arXiv:1610.02013.

4. Ilya Belopolski, et al. Topological Weyl phase transition in MoxW1-xTe2. Submitted to Nat. Mat. (2017) & arXiv:1612.07793.

5. Ilya Belopolski, et al. Criteria for directly detecting topological Fermi arcs in Weylsemimetals. Phys. Rev. Lett. 116, 066802 (2016).

6. Su-Yang Xu, Ilya Belopolski, et al. Spin polarization and texture of the Fermi arcs in the Weyl Fermion semimetal TaAs. Phys. Rev. Lett. 116, 096801 (2016).