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PbCuTe₂O₆ is a candidate quantum spin liquid (QSL) that shows no static magnetic order down to the lowest temperatures, along with signatures of fractionalized excitations [1, 2]. Recent thermodynamic measurements reveal a ferroelectric transition near 1 K, accompanied by anisotropic lattice distortions [3]. The enhanced response along the [110] direction and the divergent behavior of the Grüneisen parameter suggest proximity to a quantum critical regime and indicate that the system may be susceptible to uniaxial pressure.
In this work, we investigate the magnetic ground state under uniaxial compression along the [110] direction using muon spin rotation (μSR). With increasing stress, the ZF-μSR spectra show a pronounced enhancement of early-time depolarization, while the absence of oscillations at all applied stresses rules out the development of long-range magnetic order. At higher stress, the spectra evolve into a fast-relaxing component followed by a characteristic 1/3-tail, indicating the emergence of a broad quasi-static distribution of internal fields coexisting with persistent slow spin dynamics. Notably, the long-time relaxation remains nearly unchanged, suggesting that the fluctuation rate is largely unaffected while the static field distribution broadens significantly.
Additionally, force–displacement measurements indicate a stress-induced structural transition, beyond which the magnetic response shows clear saturation. These results suggest that uniaxial pressure lifts the degeneracy of the QSL state, driving the system toward a quasi-static regime without stabilizing conventional long-range magnetic order. This work opens new opportunities to tune both structural and magnetic interactions in frustrated systems via directional uniaxial pressure.
[1] S. Chillal et. al., Nat. Commun. 11, 2348 (2020).
[2] P. Khuntia et. al., Phys. Rev. Lett. 116, 107203 (2016).
[3] C. Thurn et. al., npj Quantum Materials 6, 95 (2021).