M. Barman | Searcharxiv

arXiv2026

Exotic magnetism and persistent spin dynamics in a frustrated Jeff = 1/2 triangular lattice antiferromagnet

The delicate interplay between competing degrees of freedom, anisotropy, and frustration-induced strong quantum fluctuations in pseudospin-$J_{\rm eff}=1/2$ rare-earth triangular-lattice antiferromagnets offers a promising platform for the experimental realization of exotic states with nontrivial low-energy excitations. Here, we present thermodynamic, inelastic neutron scattering (INS), and muon spin relaxation ($\mu$SR) investigations of the frustrated magnet K$_3$NdTe$_2$O$9$, in which Nd$^{3+}$ ions constitute a structurally perfect triangular lattice with no detectable site disorder. The experiments reveal the realization of a Kramers doublet ground state with $J{\rm eff}=1/2$ moments, well separated from the first excited state, which interact antiferromagnetically with an exchange interaction of $\sim$0.6 K between the Nd$^{3+}$ moments in the triangular plane. The absence of oscillations and the so-called 1/3 plateau in the zero-field $\mu$SR asymmetry down to 50 mK rules out long-range magnetic ordering and spin freezing on the $\mu$SR time scale, respectively. The temperature dependence of the zero-field $\mu$SR relaxation rate is well described by the Orbach relaxation mechanism, indicating the existence of fluctuating moments in the ground state of this frustrated magnet. Our results demonstrate exotic magnetism and persistent spin dynamics down to 50 mK. These observations establish this new family of frustrated rare-earth triangular-lattice antiferromagnets as a promising venue for the experimental realization of nontrivial quantum states with exotic low-energy excitations.

cond-mat.str-el↗

arXiv2026

Topological spin freezing in frustrated quantum materials

Competing interactions, non-trivial electronic band topology, quantum fluctuations, and the interplay between emergent degrees of freedom in frustrated quantum materials can give rise to a wide range of exotic phenomena. Glassy dynamics, originally studied in amorphous materials and biological systems, has recently attracted considerable interest in quantum condensed matter, particularly in relation to the collective behavior of spins, quasiparticle excitations, and topological spin textures. Here, we investigate the emergence of unconventional glassy spin dynamics in a broad class of frustrated quantum materials, where spin freezing exhibit distinct signatures in both thermodynamic and microscopic measurements. Using a comprehensive set of experimental probes, including thermodynamic, NMR, ($\mu$SR), and neutron scattering, we identify characteristic signatures of topological spin-glass behavior and these complementary techniques reveal unconventional spin dynamics, short-range spin correlations, emergent low-energy excitations, and glassy behavior of topological origins, distinguishing these states from conventional spin glasses and disordered magnets. Furthermore, we discuss the role of hydrodynamic spin modes in governing glassy dynamics and the emergence of spin-jam states in frustrated lattices, providing a unified framework for understanding unconventional spin freezing of topological origin and bridging experimental observations with theoretical models. This review aims to advance our understanding of collective many-body phenomena arising from competing interactions, topological defects, collective excitations, quantum entanglement, and symmetry constraints. Such insights may facilitate the discovery and design of novel quantum materials and help address fundamental questions in contemporary condensed matter physics, with potential implications for future quantum technologies.

cond-mat.str-el↗