Realizing and manipulating space-time inversion symmetric topological semimetal bands with superconducting quantum circuits

Abstract

Superconducting quantum circuits: appearance of a topological phase: A special topological semimetal phase is realized in superconducting quantum circuits via mimicking the momentum space with a controllable parameter space. A team led by Haifeng Yu and Yang Yu from Nanjing University and Z. D. Wang from The University of Hong Kong measured the whole energy spectrum of a square lattice made by superconducting quantum circuits. They imaged a tunable gapless band structure typical of topological semimetals. By tuning parameters, they induced a special quantum phase transition from a space-time semimetal, which is a special topological semimetal via merging a pair of Dirac points, to an insulator. They further proved the robustness of such space-time semimetal phase by breaking individual time reversal or inversion symmetry while keeping space-time symmetry intact. These results represent the first experimental realization of space-time inversion symmetric topological semimetal phase.