Disentangling the Roles and Length Scales of the Crystal Lattice, Electronic and Magnetic Degrees of Freedom in Correlated Electron Materials

We present new phenomenological descriptions of electronic phase transitions in correlated electron materials, with a focus on metal-insulator transition (MIT) materials.<br/>First, we show how to build and understand a computational energy landscape, disentangling the role of electronic and crystal lattice symmetry breaking in the MIT of rare earth nickelates <i>R</i>NiO₃, with <i>R</i> a rare-earth metal, using dynamical mean field theory [1]. We find that the electron-lattice coupling is key to stabilizing the insulating state.<br/>This theory is general, and may be applied to other materials displaying a simultaneous electronic and crystal lattice phase transition.<br/>Then, by studying multiple superlattices including rare-earth nickelates (NdNiO₃/NdAlO₃[1], NdNiO₃/SmNiO₃ [2,3] and NdNiO3/LaAlO3/SmNiO3 [4]) we clarify the interplay of the crystal lattice, electronic symmetry breaking, and magnetic degrees of freedom and the length scales of the order parameter propagation throughout the transition. We find that the electronic order parameter characterizing the transition has a dominant role in its propagation. While the magnetic order parameter is subsidiary to the electronic order parameter in the bulk, the second order nature of the magnetic transition leads to longer length scales for the magnetic degrees of freedom than that of the MIT.<br/><br/>[1] <u>A B. Georgescu</u>, Andrew J. Millis, ’Quantifying the role of the Lattice in Metal-Insulator Phase Transitions’, Communications Physics, 5, 135 (2022)<br/>[2] Claribel Dominguez Ordonez, <u>A B. Georgescu</u>, Bernat Mundet, Yajun Zhang, Jennifer Fowlie, Alain Mercy, Sara Catalano, Duncan Alexander, Philippe Ghosez, Antoine Georges, Andrew J. Millis, Marta Gibert, and Jean-Marc Triscone ’Length-scales of interfacial coupling between metal-insulator phases in oxides’, Nature Materials, 19, 1182-1187, August 2020<br/>[3] C. Dominguez, J. Fowlie, <u>A. B. Georgescu,</u> B. Mundet, N. Jaouen, M. Viret, A. Suter, A. J. Millis, M. Gibert, J. M. Triscone, ’Coupling of Magnetic Phases at Nickelate Interfaces’, In Press at Physical Review Materials, 2023, arXiv:2211.06811<br/>[4] L. Varbaro, B. Mundet, C. Dominguez, J. Fowlie, <u>A.B. Georgescu</u>, L. Korosec, D. Alexander, J.M. Triscone, ’Electronic coupling of metal-insulator transitions in nickelate based heterostructures’, Advanced Electronic Materials, 2201291, (2023)<b> </b>