Two-dimensional topological semimetal state in a nanopatterned semiconductor system

We propose the creation of a two-dimensional topological semimetal in a semiconductor artificial lattice with triangular symmetry. An in-plane magnetic field drives a quantum phase transition between the topological insulating and topological semimetal phases. The topological semimetal is characterized by robust band touching points which carry quantized Berry flux and edge states which terminate at the band touching points. The topological phase transition is predicted to occur at magnetic fields $\sim 4\text{T}$ in high mobility GaAs artificial lattices, and can be detected via the anomalous behaviour of the edge conductance.