Bosonic phases across the superconductor-insulator transition in infinite-layer samarium nickelate

TL;DR

This paper investigates bosonic phases in infinite-layer nickelate superconducting films, demonstrating the role of Cooper pairs and phase coherence in the superconductor-insulator transition, and revealing novel metallic phases influenced by vortices.

Contribution

It provides direct evidence of 2e Cooper pairing and explores bosonic phases and anomalous metallic states in nickelates across the transition.

Findings

Magnetoresistance oscillations confirm 2e Cooper pairing.

Superconducting fluctuations drive the phase transition.

Two types of anomalous metallic phases are observed.

Abstract

Superconductivity arises from the global phase coherence of Cooper pairs. Modulation of phase coherence leads to quantum phase transitions, serving as an important tool for studying unconventional superconductivity. Here, we demonstrate bosonic phases across the superconductor-insulator transition in infinite-layer nickelate superconducting films by the control of spatially periodic network patterns. Magnetoresistance oscillations with a periodicity of h/2e provide direct evidence of 2e Cooper pairing in nickelates. The phase transition is predominantly driven by enhanced superconducting fluctuations, and Cooper pairs are involved in charge transport across the transition. Notably, we observe two types of anomalous metallic phases, emerging respectively at finite magnetic fields and down to zero magnetic field. They can be characterized by bosonic excitations, suggesting the dynamic roles of vortices in the ground states. Our work establishes nickelates as a key platform for investigating the rich landscape of bosonic phases controlled via the phase coherence of Cooper pairs.