[Paper Review] Observation of high-temperature superconductivity in the high-pressure tetragonal phase of La2PrNi2O7-δ

Gang Wang, Ningning Wang+15 more|arXiv (Cornell University)|Nov 14, 2023

Magnetic and transport properties of perovskites and related materials11 citations

TL;DR

The paper reports high-temperature superconductivity in the high-pressure tetragonal I4/mmm phase of La2PrNi2O7-δ above ~10 GPa, with Tc_onset of 78.2 K and Tc_zero of 40 K at 15 GPa, distinguishing it from the orthorhombic phase in a related compound. This provides a new nickelate platform with cuprate-like symmetry for exploring superconductivity mechanisms.

ABSTRACT

The recent discovery of high-temperature superconductivity in the Ruddlesden-Popper phase La3Ni2O7 under high pressure marks a significant breakthrough in the field of 3d transition-metal oxide superconductors. For an emerging novel class of high-Tc superconductors, it is crucial to find more analogous superconducting materials with a dedicated effort toward broadening the scope of nickelate superconductors. Here, we report on the observation of high-Tc superconductivity in the high-pressure tetragonal I4/mmm phase of La2PrNi2O7 above ~10 GPa, which is distinct from the reported orthorhombic Fmmm phase of La3Ni2O7 above 14 GPa. For La2PrNi2O7, the onset and the zero-resistance temperatures of superconductivity reach Tconset = 78.2 K and Tczero = 40 K at 15 GPa. This superconducting phase shares the samilar structural symmetry as many cuprate superconductors, providing a fresh platform to investigate underlying mechanisms of nickelate superconductors.

Motivation & Objective

• Motivate the search for nickelate superconductors with cuprate-like structural symmetry under high pressure.
• Demonstrate superconductivity in La2PrNi2O7-δ and map its phase behavior with pressure.
• Compare the high-pressure tetragonal phase with known phases in related nickelates to understand structural effects on superconductivity.

Proposed method

• High-pressure synthesis/measurement up to beyond 10 GPa to stabilize the tetragonal I4/mmm phase.
• Electrical transport measurements to identify onset and zero-resistance temperatures.
• Structural characterization to determine phase symmetry and its relation to superconductivity.
• Comparison to orthorhombic Fmmm phase in La3Ni2O7 to highlight phase-dependent superconductivity.

Experimental results

Research questions

• RQ1 Can high-temperature superconductivity be stabilized in La2PrNi2O7-δ under high-pressure tetragonal symmetry?
• RQ2 What are the onset and zero-resistance temperatures as a function of pressure for this phase?
• RQ3 How does the tetragonal phase relate to cuprate-like superconductivity in nickelates?
• RQ4 How does this phase compare to the orthorhombic phase observed in La3Ni2O7 at higher pressures?

Key findings

• Superconductivity observed in the high-pressure tetragonal I4/mmm phase of La2PrNi2O7-δ above ~10 GPa.
• At 15 GPa, Tc_onset = 78.2 K and Tc_zero = 40 K.
• The superconducting phase shares structural symmetry akin to many cuprate superconductors.
• This phase is distinct from the orthorhombic Fmmm phase of La3Ni2O7, which appears above 14 GPa.
• The study highlights La2PrNi2O7-δ as a fresh platform to study nickelate superconductors and their mechanisms.