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

• Main Authors: Hussain, Riaz, Prando, Giacomo, Selter, Sebastian, Aswartham, Saicharan, Büchner, Bernd, Carretta, Pietro
• Format: Journal Article
• Language: English
• Published: 02.10.2020
• Subjects: Physics - Strongly Correlated Electrons; Physics - Superconductivity
• DOI: 10.48550/arxiv.2010.00968

Phys. Rev. B 103, 081105 (2021) 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.