Work

Finite-Size Spectral Signatures of Order by Quantum Disorder: A Perspective from Anderson’s Tower of States

Year: 2026

Type: article

Abstract: In frustrated magnetic systems with a subextensive number of classical ground states, quantum zero-point fluctuations can select a unique long-range ordered state, a celebrated phenomenon referred to as order by quantum disorder (ObQD). For frustrated spin-1/2 models, unbiased numerical methods able to expose ObQD are necessary. We show that ObQD can be identified from exact diagonalization calculations through an analysis akin to the Anderson tower of states associated with spontaneous symmetry breaking. By defining an effective quantum rotor model, we describe the competition between ObQD-induced localization of the rotor and its tunneling between symmetry-related ground states, identifying the crossover length scale from the finite-size regime where the rotor is delocalized to the infinite system-size limit where it becomes localized. This rotor model relates the characteristic splittings in the exact diagonalization energy spectrum to the ObQD selection energy scale, providing an estimate that can be compared to spin wave calculations. We demonstrate the general applicability of this approach in one-, two-, and three-dimensional frustrated spin models that exhibit ObQD.

Source: Physical Review Letters

DOI: 10.1103/rdyh-2fqj

Authors: Subhankar Khatua, Griffin C. Howson, Michel J. P. Gingras, Jeffrey G. Rau

Institutions: University of Waterloo, Leibniz Institute for Solid State and Materials Research, Complexity, Topology and Dynamics in Quantum Matter, University of Windsor

Language: English

Topic: Advanced Condensed Matter Physics

Subfield: Condensed Matter Physics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $3,750