Pressure-induced monotonic enhancement of Tc to over 30 K in the superconducting Pr0.82Sr0.18NiO2 thin films

Abstract

The successful synthesis of superconducting nickelate thin films with the highest Tc ~ 15 K has reignited great enthusiasms on this class of potential analogue to high-Tc cuprates suggested decades ago. To pursue higher Tc is always an important task in studying new superconductors. Here we report for the first time the effect of pressure on the superconducting properties of infinite-layer Pr0.82Sr0.18NiO2 thin films by measuring electrical resistivity under various pressures in a cubic anvil cell apparatus. We find that the onset of superconductivity, Tconset, can be enhanced monotonically from ~ 18 K at ambient pressure to ~ 31 K without showing signatures of saturation upon increasing pressure to 12.1 GPa in the presence of liquid pressure transmitting medium. This encouraging result indicates that the Tc of infinite-layer nickelates superconductors can be further raised up by applying higher pressures or strain engineering in the heterostructure films. In addition to the pressure effect, we also discussed the influence of stress/strain on the superconducting properties of the nickelate thin films.

Infinite-Layer Nickelate Superconductors: A Current Experimental Perspective of the Crystal and Electronic Structures

“…For decades, theoretical and experimental efforts have been made to explore the lead [11][12][13]. Unlike cuprate, which was first synthesized in the bulk form, superconducting nickelate was only realized recently in the thin-film form [14][15][16][17][18][19][20][21], with Ni 1+ in the infinite-layer phase that can be achieved through topotactic reduction from the perovskite compound. Missing superconductivity in the bulk nickelate [22,23] and limitation in stabilizing the infinite-layer phase above ~10 nm from the substrate [24][25][26] demands answers on the thickness-dependent crystallinity and electronic structure of the infinite-layer nickelate film.…”

“…Despite the long search, La-nickelate was initially found not to be superconducting and the first observation of nickelate superconductivity was realized by Sr-doped on a smaller neodymium ion Nd-infinite-layer nickelate thin film with 4f magnetism in 2019 [14]. Since then, superconductivity in the infinite-layer nickelate family has been quickly expanded to another neighbor with rare-earth magnetism in the rare-earth series, praseodymium (Pr) [42], and has been successfully reproduced by multiple experimental groups [17,51]. However, superconductivity in La-nickelate, which has an empty 4f orbital, still seems non-existent for another 2 years until it was successfully realized independently by two different groups in the Ca-doped La 1-x Ca x NiO 2 [16] and Sr-doped La 1-x Sr x NiO 2 [41] infinite-layer thin film.…”

“…It seems early to suggest any strict correlation between the superconducting dome of infinite-layer nickelate and the c-axis lattice dimension. It is worth noting that an enhancement in onset T c was realized experimentally by applying external pressure [17], which suggests the likelihood of further increasing T c by simulating chemical pressure through tuning in-plane lattice constants, rare-earth ions size, or dopant size. In addition, we note that there are recent theoretical calculations on the effect of in-plane lattice constant and epitaxial strain in tuning the P4/ mmm -I4/mcm phase transition in RNiO 2 (R = La, Pr, Nd, Eu-Lu, Y) [56,57].…”