Excitation spectrum and spin Hamiltonian of the frustrated quantum Ising magnet PrBWO

Nagl, J.*; Flavin, D.*; Hayashida, S.*; Povarov, K. Y.*; Yan, M.*; Murai, Naoki  ; Kawamura, Seiko   ; Simutis, F.*; Hicken, T. J.*; Luetkens, H.*; Baines, C.*; Hauspurg, A.*; Schwarze, B. V.*; Husstedt, F.*; Pomjakushin, V.*; Fennell, T.*; Yan, Z.*; Gvasaliya, S.*; Zheludev, A.*

We investigate the rare-earth-based frustrated quantum antiferromagnet PrBWO, previously considered a spin-liquid candidate. Our experimental and theoretical analysis reveals that its ground state is better described as a quantum paramagnet, governed by an Ising model in a transverse field. While in-plane correlations exist, the dominant interactions form frustrated triangular spin tubes via competing ferro-antiferromagnetic bonds. The system's thermodynamic and dynamic properties are significantly influenced by hyperfine interactions and weak structural disorder.