Magnetically-induced local lattice anomalies and low-frequency nematic fluctuations in the Mott insulator La${}_2$O${}_3$Fe${}_2$Se${}_2$

Abstract

We report a study of the Mott insulator La${}_2$O${}_3$Fe${}_2$Se${}_2$ by means of ${}^{139}$La nuclear quadrupole resonance (NQR). The NQR spectra evidence a single La site in the paramagnetic phase and two inequivalent La sites, La1 and La2, in the antiferromagnetically-ordered phase (Néel temperature $T_{\mathrm{N}}\simeq 90$ K). These two sites are characterized by different quadrupole couplings, indicative of distinct lattice and/or charge configurations likely segregated in domains. The dependence of the quadrupole coupling for La2 on temperature suggests that the magnetic order parameter drives the structural distortion. The nuclear spin-lattice and transverse relaxation rates, $1/T_1$ and $1/T_2$, evidence fluctuations in the paramagnetic phase with characteristic frequencies well below the Heisenberg exchange frequency, likely associated with nematic fluctuations.

6 pages, 4 figures

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Cited by in corpus (1)

• Pressure-induced transition from a Mott insulator to a ferromagnetic Weyl metal in La2O3Fe2Se2