SFB Colloquium

Fundamental research and technological applications of topological insulators are hindered by the rarity of materials exhibiting a robust topologically nontrivial phase, especially in two dimensions. In this seminar, I will show how—by means of extensive first-principles calculations—we screen a comprehensive database we recently developed of 1825 exfoliable two-dimensional materials [2] to search for novel quantum spin Hall insulators (QSHIs). I will discuss the most outstanding novel QSHI candidate, with a sizable band gap of 0.5 e ∼ V, that is a monolayer of jacutingaite [1], a naturally occurring layered mineral first discovered in 2008 in Brazil and recently synthesized. This system realizes the paradigmatic Kane-Mele [3,4] model for quantum spin Hall insulators in a potentially exfoliable twodimensional monolayer, with helical edge states that are robust and that can be manipulated exploiting a unique strong interplay between spin-orbit coupling, crystal-symmetry breaking, and dielectric response [1]. Finally, I will mention how temperature effects could affect the QSHI phase of monolayer jacutingaite and give and an update on ongoing experimental efforts. Possible experimental and theoretical collaborations will also be discussed.

[1] A. Marrazzo, M. Gibertini, D. Campi, N. Mounet and N. Marzari, Phys. Rev. Lett. 120, 117701 (2018)
[2] N. Mounet, M. Gibertini, P. Schwaller, D. Campi, A. Merkys, A.Marrazzo, T. Sohier, I. E. Castelli, A. Cepellotti, G. Pizzi, and N. Marzari, Nature Nanotechnology 13, 246 (2018).
[3] C. L. Kane and E. J. Mele, Phys. Rev. Lett. 95, 226801 (2005).
[4] C. L. Kane and E. J. Mele, Phys. Rev. Lett. 95, 146802 (2005).