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Colloquium: Exploring Relativistic Physics in Dirac Systems: Coexistence of Massless and Massive Electrons in Topological Crystalline Insulators

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Vidya Madhavan, University of Illinois, Urbana-Champaign
When
11 September 2014 from 4:00 PM to 5:00 PM
Where
117 Osmond Laboratory
Contact Name
Contact Phone
863-1089
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In Dirac materials like graphene and topological insulators, electrons behave like relativistic particles with no mass. This is a direct consequence of the form of the low energy effective Hamiltonian describing these electrons and has important implications for realizing physical properties predicted for high-energy particles, now in the laboratory setting.  Topological crystalline insulators are recently discovered topological materials [1,2] where topology and crystal symmetry intertwine to create relativistic massless electrons. Among the theoretical predictions for topological crystalline insulators is the possibility of imparting mass to these massless Dirac fermions by breaking crystal symmetry. In this talk I will discuss our recent experimental and theoretical investigations of a topological crystalline insulators, Pb1-xSnxSe [3,4]. We performed scanning tunneling microscopy (STM) studies at low temperatures and as a function of magnetic field. With the help of our high-resolution data, I will show how zero-mass electrons and massive electrons can coexist in the same material. I will discuss the conditions to obtain these zero mass electrons as well the method to impart a controllable mass to the particles and show how our studies create a path to engineering the Dirac band gap and realizing interaction-driven topological quantum phenomena in TCIs.

[1] L. Fu, Topological Crystalline Insulators. Phys. Rev. Lett. 106, 106802 (2011).

[2] T. H. Hsieh et al., Topological crystalline insulators in the SnTe material class. Nat.Commun. 3, 982 (2012).

[3] Y. Okada, et al., Observation of Dirac node formation and mass acquisition in a topological crystalline insulator. Science 341, 1496-1499 (2013)

[4] Ilija Zeljkovic et al., Mapping the unconventional orbital texture in topological crystalline insulators. Nature Physics 10, 572–577 (2014)

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