Shang-Qiang Ning

Sep 12, 2024 | link.aps.org | Zhe Wang |Shang-Qiang Ning |Zenan Liu

We design a (2+1)-dimensional [(2+1)D] quantum spin model in which spin-1/2 ladders are coupled through antiferromagnetic Ising interactions. The model hosts a quantum phase transition in the (2+1)D Z2 universality class from the Haldane phase to the antiferromagnetic Ising ordered phase. We focus on studying the surface properties of three different surface configurations when the Ising couplings are tuned. Different behaviors are found on different surfaces.

Jun 6, 2023 | link.aps.org | Pokfulam Road |Yang Qi |Shang-Qiang Ning

Abstract It is well known that two-dimensional fermionic systems with a nonzero Chern number must break the time-reversal symmetry, manifested by the appearance of chiral edge modes on an open boundary. Such an incompatibility between topology and symmetry can occur more generally. We will refer to this phenomenon as enforced symmetry breaking (ESB) by topological orders. In this work, we systematically study ESB of a finite symmetry group Gf by fermionic invertible topological orders.