Abstract: In 1988 in a seminal paper by D. Haldane [PRL 61, 2015 (1988)] a topological phase was proposed for non-interacting fermions in the honeycomb lattice where, although time reversal symmetry is broken, the magnetic field is zero on average. Twenty years later such quantum anomalous Hall phase was predicted to be realized through a spontaneous time reversal symmetry-breaking as a result of interactions between fermions [Raghu et al., PRL 100, 156401 (2008)]. Here we will show, based on a variational mean-field approach, that charge modulated phases with reduced translational symmetry compete strongly with topological phases in the honeycomb lattice, indicating that the latter are not as robust as anticipated. Tuning the fermion density enables topological Fermi liquid phases to set in, but severe fine tuning is imposed by the competition with non-topological phases. These findings are a call for alternative unbiased methods to address the problem.

 

About the Speaker: Eduardo V. Castro obtained his PhD in Physics in 2008 from University of Porto, Portugal. He joined the MPI-PKS in Dresden, Germany, as a visitor post-doc, and later became a Juan de la Cierva researcher at ICMM-CSIC, Spain. Since 2012 he is Assistant professor at IST-Lisbon, Portugal. He is member of the Research Center CFIF at IST-Lisbon, Portugal, and Associate Member of CSRC, Beijing, since 2012. His main research topics in the Theory of Condensed Matter include graphene and related 2D materials, topological insulators and superconductors, electron correlations.  

  

Date&Time: July 24, 2013 (Wednesday), 16:30 - 17:30
Location: 606 Conference Room