Extending the metal to insulator transitions of rare‐earth nickelates towards low temperature ranges

Abstract

Although the d‐band correlated rare‐earth nickelates (ReNiO3) exhibit broadly adjustable metal to insulator transitions (MIT) that enables emerging correlated electronic applications, it is yet difficult to regulate their associated critical temperature (TMIT) below 100 K. Herein, we extend the lower limit in TMIT of ReNiO3 down to 83 K while maintaining an abrupt switch in resistivity via partial La‐substitution of PrNiO3. The near edge X‐ray fine structure analysis and density function theory calculations indicate the strengthening in the metallic orbital configuration and reduction in the ground state band gap via La‐substitution of Re in NdNiO3 and PrNiO3. In contrast, analogous Ce substitution cannot reduce the TMIT of ReNiO3 owing to its valance variability toward +4, while La partial substitution of ReNiO3 with middle or heavy rare‐earth (e.g., Sm) easily disturb the co‐occupation of the Re‐site by the two rare‐earths as one dispersive phase.

Revealing the Role of the Tetragonal Distortion in the Metal–Insulator Transition of Co- and Fe-Doped NiS

“…From the above results, it can be seen that the magnitude of LT MIT (σ Met – σ Ins ) is critical to achieve a high regulation rate in κ. In Figure b, the LT MIT (σ Met – σ Ins ) is summarized for the NiS material herein, compared with the existing family of MIT materials, and plotted as a function of T MIT . − It can be seen that the NiS is the only promising candidate to achieve a synchronized switch in thermal conductivity to MIT, as far as we were concerned. In contrast, the variation in κ C across MIT is not comparable to their κ Ins for most of the existing MIT oxides (e.g., Re NiO 3 , Ca n +1 Ru n O 3 n +1 and Nd 0.5 Sr 0.5 MnO 3 ), because of their low conductivity, even at the metallic phase.…”

In Situ High-Pressure Correlated Transportation of Heavy Rare-Earth Perovskite Nickelates as Batch Synthesized within Eutectic Molten Salts at MPa-pO2

“…3,7 An overwhelming advantage in the MIT functionality of ReNiO 3 is the broad adjustability in their T MIT continuously within a wide temperature range of 100−600 K by simply adjusting the composition of Re. 8,9 A smaller ionic radius of Re distorts the NiO 6 more, which reduces the orbital overlapping between the Ni-3d and O-2p and results in a more stable insulating phase with higher T MIT . 2,4,8,9 Apart from the above band gap regulations, the electronic transportation properties of ReNiO 3 can be more directly switched among multiple electronic states via Mottronic orbital filling control.…”

“…8,9 A smaller ionic radius of Re distorts the NiO 6 more, which reduces the orbital overlapping between the Ni-3d and O-2p and results in a more stable insulating phase with higher T MIT . 2,4,8,9 Apart from the above band gap regulations, the electronic transportation properties of ReNiO 3 can be more directly switched among multiple electronic states via Mottronic orbital filling control. 3,7,10,11 For example, the d-orbital occupancy within ReNiO 3 can be increased from Ni 3±Δ t 2g 6 e g 1±Δ (or Ni 3+ t 2g 6 e g 1 ) to Ni 2+ t 2g 6 e g 2 via reversable hydrogenation that triggers strong electron localization, 3,7 while a superconductive phase associated with the Ni 1+ t 2g 6 e g 3 can be even formed via heavier hydrogenation.…”

“…Breaking the thermodynamic restriction and establishing the metastable or unstable electronic phases within electron-correlated semiconductors open up a new paradigm to the exploration of new material functionalities and device applications beyond the conventional . As a representative metastable perovskite, the rare-earth nickelates ( Re NiO 3 ) exhibit an extra-ordinarily complex electrical phase diagram and multiple electronic phase transitions, originating from the high tolerance in manipulating its Ni-3d/O-2p orbital configurations via their NiO 6 octahedron. − The charge disproportionation (antidisproportionation) associated with Ni 3+ t 2 g 6 e g 1 ↔ Ni 2+ t 2 g 6 e g 2 triggered via critical temperatures ( T MIT ) enables the metal-to-insulator transition (MIT) of Re NiO 3 . , An overwhelming advantage in the MIT functionality of Re NiO 3 is the broad adjustability in their T MIT continuously within a wide temperature range of 100–600 K by simply adjusting the composition of Re . , A smaller ionic radius of Re distorts the NiO 6 more, which reduces the orbital overlapping between the Ni-3d and O-2p and results in a more stable insulating phase with higher T MIT . ,,, Apart from the above band gap regulations, the electronic transportation properties of Re NiO 3 can be more directly switched among multiple electronic states via Mottronic orbital filling control. ,,, For example, the d-orbital occupancy within Re NiO 3 can be increased from Ni 3±Δ t 2 g 6 e g 1±Δ (or Ni 3+ t 2 g 6 e g 1 ) to Ni 2+ t 2 g 6 e g 2 via reversable hydrogenation that triggers strong electron localization, , while a superconductive phase associated with the Ni 1+ t 2 g 6 e g 3 can be even formed via heavier hydrogenation. , These recent discoveries extend the fundamental vision in the field of condensed matter physics and also enrich new electronic applications, such as correlated electronics for artificial intelligence, , ocean current electric field sensor, correlated electronics for energy conversion, and biosensing …”