2020/11/26 by Shunsuke C. Furuya, Furuya, Shunsuke C., Yusuke Horinouchi +3
Physics and Astronomy · #Advanced Condensed Matter Physics #FOS: Physical sciences #Quantum many-body systems #Statistical Mechanics (cond-mat.stat-mech) #Strongly Correlated Electrons (cond-mat.str-el) #Topological Materials and Phenomena
paper · pdf · doi:10.48550/arxiv.2011.13095
openalex publication_date 2020/11/26 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We discuss the ground-state degeneracy of spin-1/2 kagome-lattice quantum antiferromagnets on magnetization plateaus by employing two complementary methods: the adiabatic flux insertion in closed boundary conditions and a 't Hooft anomaly argument on inherent symmetries in a quasi-one-dimensional limit. The flux insertion with a tilted boundary condition restricts the lower bound of the ground-state degeneracy on 1/9, 1/3, 5/9, and 7/9 magnetization plateaus under the U(1) spin-rotation and the translation symmetries: 3, 1, 3, and 3, respectively. This result motivates us further to develop an anomaly interpretation of the 1/3 plateau. Taking advantage of the insensitivity of anomalies to spatial anisotropies, we examine the existence of the unique gapped ground state on the 1/3 plateau from a quasi-one-dimensional viewpoint. In the quasi-one-dimensional limit, kagome antiferromagnets are reduced to weakly coupled three-leg spin tubes. Here, we point out the following anomaly description of the 1/3 plateau. While a simple S=1/2 three-leg spin tube cannot have the unique gapped ground state on the 1/3 plateau because of an anomaly between a \mathbb Z3× \mathbb Z3 symmetry and the translation symmetry at the 1/3 filling, the kagome antiferromagnet breaks explicitly one of the \mathbb Z3 symmetries related to a \mathbb Z3 cyclic transformation of spins in the unit cell. Hence the kagome antiferromagnet can have the unique gapped ground state on the 1/3 plateau.