Heterostructuring and strain effects on the infrared optical properties of nickelates

Abstract

An optical study of the effects of strain and heterostructuring on nickelates is presented. The optical conductivity data obtained for a series of ultrathin films of NdNiO 3 with varying amounts of strain reveal that two mechanisms, each associated with a different energy scale, are responsible for the tuning of the Drude-like spectral weight as a function of strain. Additionally, the optical properties of the LaNiO 3 layers in a LaNiO 3 /LaAlO 3 superlattice are investigated, showing that the coherent Drude transport associated with strained LaNiO 3 is suppressed due to the presence of the LaAlO 3 interlayers.

Tuning the metal-insulator transition inNdNiO3heterostructures via Fermi surface instability and spin fluctuations

“…Earlier angle-integrated photoemission studies of Nd 1−x Sm x NiO 3 show similar behavior of the spectral weight transfer from near E F region to higher binding energy region [36]. Our observation is also consistent with an optical study, where the MIT is argued to be linked to a spectral weight transfer from the Drude region (coherent state) to the deeper energy [11,31].…”

“…The result is suggestive of the presence of a 'hidden' quantum critical point as a function of strain [6]. Interestingly, optical spectroscopies have identified that the MIT is associated with a spectral weight transfer from the mid-infrared region to a higher energy scale [11,31].…”

Physics of Ultrathin Films and Heterostructures of Rare-Earth Nickelates

“…However, as some chemical nonstochiometry may be introduced during the growth, actual should be calculated using the experimentally measured lattice constant of an unstrained film (instead of a bulk ). The effect of strain on electronic and magnetic transitions of RENiO 3 series has been thoroughly explored by diverse experimental probes including thermal measurements and Hall effect measurement [58,64,65], synchrotron X-ray diffraction [66,67], X-ray absorption spectroscopy [67][68][69][70][71], resonant soft X-ray scattering [69,72,73], ARPES [74,75], optical spectroscopy [72,[76][77][78].…”

Negative magnetoresistance in epitaxial films of neodymium nickelate

“…9(b)]. Considering a gap E g of 30-100 meV in the insulating phase of the NNO films [28,29], the Fermi level may reach the conduction band at the temperatures when the macroscopic metal-range conduction becomes observable on heating (Fig. 3).…”