ELFT HÍRADÓ

[Edina Szirmai <eszirmai AT phy.bme.hu>]

                        MEGHÍVÓ

   az BME-MTA "Egzotikus Kvantum Fázisok"
    kutatócsoport következő szemináriumára:


                    Varjas Dániel
      (University of California, Berkeley)

Space group constraints on topological response
   in crystalline insulators and superconductors



Kivonat:
Classification of solids by crystal symmetry has been well understood for
decades but its relationship to band topology is still unexplored to a
large extent. Classifying topological crystalline phases is a natural next
step towards understanding symmetry protected topological order of
fermions, a program fueled by recent advances in sample growth and
experimental techniques. We show that the surface Hall response of 3
dimensional insulators becomes half-integer quantized even in the absence
of time reversal symmetry if any orientation-reversing lattice symmetry is
present. This remains true if the symmetry is non-symmorphic, we
demonstrate this by explicit computation using glide-symmetric
tight-binding models. We construct analogous examples of glide protected
topological crystalline superconductors in classes D and C and discuss how
bulk invariants are related to quantized surface thermal-Hall and spin-Hall
responses. We also derive constraints on weak indices of topological
insulators and superconductors coming from space group symmetry. We find
that most space groups experience some restriction, to the extent that some
cannot support nontrivial weak topological insulators and superconductors
at all. This result puts a strong constraint on candidates in the
experimental and numerical search for topological materials based on the
lattice structure alone.

Az előadás helye:  BME F III. épület, mfsz, szemináriumi szoba.
Ideje: 2016. január 11. hétfő, 14:15.


Minden érdeklődőt szeretettel várunk!

                         Szirmai Edina




-- 
Edina Szirmai
Department of Theoretical Physics,
Budapest University of Technology and Economics
Budafoki ut 8.
Budapest, Hungary
Tel:(+36-1) 463-4107
Fax:(+36-1) 463-3567
www.phy.bme.hu/~eszirmai