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arXiv · 2010.00968

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

Riaz Hussain·Giacomo Prando·Sebastian Selter·Saicharan Aswartham·Bernd Büchner·Pietro Carretta
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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 (N\'eel temperature $T_{\rm{N}} \simeq 90$ 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.

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Riaz Hussain, Giacomo Prando, Sebastian Selter, Saicharan Aswartham, Bernd Büchner, Pietro Carretta. 2020-10-02. Magnetically-induced local lattice anomalies and low-frequency nematic fluctuations in the Mott insulator La$_2$O$_3$Fe$_2$Se$_2$. https://doi.org/10.1103/physrevb.103.l081105

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