Half-quantized Hall effect at the parity-invariant Fermi surface

Condensed matter realization of a single Dirac cone of fermions in two dimensions is a long-standing issue. Here we report the discovery of a single gapless Dirac cone of half-quantized Hall conductance in a magnetically doped topological insulator heterostructure. It demonstrates that the Hall conductance is half-quantized in the unit e2/h when the parity symmetry is preserved near the Fermi surface. The gapless Dirac point is stable and protected by the local parity symmetry and the topologically nontrivial band structure of the topological insulator. The one-half Hall conductance observed in a recent experiment [M. Mogi et al., Nat. Phys. 18, 390 (2022)] is attributed to the existence of the gapless Dirac cone and the parity invariance of the Fermi surface. The results suggest a condensed matter realization of a topological phase with a one-half topological invariant.

Automated summary

Here, we report the discovery of a single gapless Dirac cone of half-quantized Hall conductance in a magnetically doped topological insulator heterostructure. It is found that the Hall conductance is half-quantized when the parity symmetry is preserved near the Fermi surface. The gapless Dirac point is protected by local parity symmetry and the topologically nontrivial band structure of the topological insulator. The recent experiment confirms the existence of the gapless Dirac cone and the parity invariance of the Fermi surface, leading to the observation of half Hall conductance [M. Mogi et al., Nat. Phys. 18, 390 (2022)]. These findings suggest a condensed matter realization of a topological phase with a one-half topological invariant.