Who: Xiao Hu (International Center for Materials Nanoarchitectonics (WPI-MANA) National Institute for Materials Science (NIMS), Tsukuba, Japan)
Place: Donostia International Physics Center (DIPC)
Date: Monday, 6 July 2015, 12:00
International Center for Materials Nanoarchitectonics (WPI-MANA)
National Institute for Materials Science (NIMS), Tsukuba, Japan
How simple can a useful topological system be? In this talk I try to answer this question based on our recent work on achieving quantum spin Hall effects by simply deforming honeycomb lattice. We observe that honeycomb lattice is equivalent to triangle lattice of hexagons formed by six neighboring sites. When the triangle lattice is squeezed with the hexagons fixed and C6 symmetry preserved, a gap will be opened in the Dirac energy dispersion, and simultaneously a pseudo spin degree of freedom will be generated in the system. The first implementation of this idea is a topological photonic crystal based on conventional dielectric material, such as silicon, which carries on edge counter-propagation of electromagnetic waves with opposite pseudo spins. In the second example, we modify the electron hopping integral between nearest-neighboring sites of honeycomb lattice in a way to build Kekule hopping texture. It is shown that an effective spin-orbit coupling (SOC) is generated, larger than the intrinsic SOC by several orders of magnitude, which may make helical edge currents available at high temperature.