Pseudo-gap in RuGa3: A microscopic point of view

• Published in: Journal of alloys and compounds 2023-03, Vol.938, p.168522, Article 168522
• Main Authors: Gippius, A.A., Tkachev, A.V., Zhurenko, S.V., Gunbin, A.V., Demikhov, E.I., Kuo, C.-N., Lue, C.-S., Nguyen, N.-Q., Luo, C.-W., Khrustalev, V.N., Svetogorov, R.D., Likhanov, M.S., Shevelkov, A.V.
• Format: Article
• Language: English
• Subjects: In-gap states; Intermetallics; NMR; NQR; Pseudo-gap; Pump-probe spectroscopy
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2022.168522

We report a detailed study of the nature of the RuGa3in-gap states by means of precision microscopic methods: nuclear quadrupole resonance (NQR), nuclear magnetic resonance (NMR), and pump-probe spectroscopy. We observe a pronounced splitting of 69Ga nuclear spin-lattice relaxation curves below ∼40 K and between 70 and 145 K, although the corresponding NQR lines remain narrow over the entire temperature range under study. The slow relaxing component behaves like a typical phonon-induced relaxation way, while the fast relaxing one demonstrates signatures of paramagnetic (below ∼40 K) and activation (between 70 and 145 K) mechanisms. Moreover, additional Ga’ and Ga’’ positions with anomalously low electric field gradient were revealed for the first time for IrIn3-type structure gallides, which stay almost unchanged, at least up to 77 K. The observed microscopic features are accompanied with in-gap states saturation or depleting, which is seen as the resistivity mechanism crossover at ∼180 K and electron localization below 145 K evidenced by pump-probe spectroscopy. Based on our experimental results, we associate this pseudo-gap like behavior with inhomogeneously distributed electronic density defects, which manifest at both micro- (nuclear spin and phonon dynamics) and macroscale (bulk transport properties such as resistivity). •Anomalous splitting of 69Ga spin-lattice relaxation curves without line broadening.•Additional Ga positions with anomalously low electric field gradient were revealed.•In-gap states are formed by inhomogeneously distributed electronic density defects.•These defects demonstrate paramagnetic behavior at the lowest temperatures.