ELFT HÍRADÓ

[Janos Asboth <asboth.janos AT ttk.bme.hu>]

Meghívó

BME Elméleti Fizika Szeminárium,

máj. 24. péntek 10h15,

1111 Budapest, Budafoki út 8., BME F III. magasföldszint 01.,
Elméleti Fizika Tanszék szemináriumi szoba

Varjas Dániel (BME Elm. Fiz. tanszék)
Isotropic 3D topological phases with broken time reversal symmetry

Axial vectors, such as current or magnetization, are commonly used order
parameters in time-reversal symmetry breaking systems. These vectors also
break isotropy in three dimensional systems, lowering the spatial symmetry.
We demonstrate [1] that it is possible to construct a fully isotropic and
inversion-symmetric three-dimensional medium where time-reversal symmetry
is systematically broken. We devise a cubic crystal with scalar
time-reversal symmetry breaking, implemented by hopping through chiral
magnetic clusters along the crystal bonds. The presence of only the spatial
symmetries of the crystal -- finite rotation and inversion symmetry -- is
sufficient to protect a topological phase. The realization of this phase in
amorphous systems with average continuous rotation symmetry yields a
statistical topological insulator phase. We demonstrate the topological
nature of our model by constructing a bulk integer topological invariant,
which guarantees gapless surface spectrum on any surface with several
overlapping Dirac nodes, analogous to crystalline mirror Chern insulators.
We also show the expected transport properties of a three-dimensional
statistical topological insulator, which remains critical on the surface
for odd values of the invariant.

[1]: H Spring, AR Akhmerov, D Varjas, arXiv:2310.18400

Minden érdeklődőt szeretettel várunk.
Asbóth János,
 szemináriumi koordinátor