Tunable resistivity exponents in the metallic phase of epitaxial nickelates

Summary

Rare earth nickelates (ReNiO3) undergo a metal-insulator transition (MIT) that can be tuned
both chemically (choice of Re) and physically (strain or electric field). Nickelates hold great
promise for resistive switching applications, such as for memories or adaptable electronics.
The interest on these materials has recently increased even further due to the finding of
superconductivity on the related family of infinite-layer nickelates[1]. However, a complete
understanding of the metallic phase in these strongly correlated electron systems is still one
of the central open problems in condensed matter physics. For instance, nickelates have been
proposed to behave both as bad metals[2] and as normal metals[3] by different researchers.
Moreover, the behavior of the nickelates as Fermi-liquid or non-Fermi liquid systems is also
highly debated, as various scaling exponents of the resistivity as a function of temperature
have been reported in the same materials [3,4].

In this talk, I will show that the resistivity-temperature exponent in epitaxially-grown NdNiO3
films can be continuously tuned by the combined effect of epitaxial strain and disorder[5],
validating previous theoretical results by Patel et al [6]. Therefore, the assignment of Fermi
liquid/non-Fermi liquid behavior from the resistivity-temperature exponents is not always
justified and a detail micro-structural characterization is needed. In addition, I will describe
our latest experiments that aim to establish the nature of the metallic behavior in the NdNiO3.

[1] D. Li, et al., Nature 572, 624 (2019).
[2] R. Jaramillo, et al., NPhysics 10, 304 (2014).
[3] E. Mikheev, et al., Sci, Adv. 1, e1500797 (2015).
[4] J. Liu, et al., NComms. 4, 2714 (2013).
[5] Q. Guo, B. Noheda, et al., https://arxiv.org/abs/1909.06256.
[6] N.D. Patel, et al., Phys. Rev. Lett. 119, 086601 (2017).