Charge $4e$ superconductivity from pair density wave order in certain high temperature superconductors

TL;DR

This paper predicts a novel charge 4e superconducting state arising from the melting of striped superconductivity in cuprates, characterized by fractional flux quantum, challenging conventional BCS theory and suggesting new experimental tests.

Contribution

It introduces the concept of charge 4e superconductivity resulting from stripe order melting, a state not explained by traditional BCS theory, with proposed experimental verification methods.

Findings

Prediction of charge 4e superconductivity with fractional flux quantum

Identification of novel phases from melting striped superconducting state

Proposal for experiments to detect fractional flux quantization

Abstract

A number of spectacular experimental anomalies\cite{li-2007,fujita-2005} have recently been discovered in certain cuprates, notably {\LBCO} and {\LNSCO}, which exhibit unidirectional spin and charge order (known as ``stripe order''). We have recently proposed to interpret these observations as evidence for a novel ``striped superconducting'' state, in which the superconducting order parameter is modulated in space, such that its average is precisely zero. Here, we show that thermal melting of the striped superconducting state can lead to a number of unusual phases, of which the most novel is a charge $4e$ superconducting state, with a corresponding fractional flux quantum $hc/4e$. These are never-before observed states of matter, and ones, moreover, that cannot arise from the conventional Bardeen-Cooper-Schrieffer (BCS) mechanism. Thus, direct confirmation of their existence, even in a small subset of the cuprates, could have much broader implications for our understanding of high temperature superconductivity. We propose experiments to observe fractional flux quantization, which thereby could confirm the existence of these states.