Fluctuating Charge Order: A Universal Phenomenon in Unconventional Superconductivity?

Abstract

Unconventional superconductors are characterized by various competing ordering phenomena in the normal state, such as antiferromagnetism, charge order, orbital order or nematicity. According to a widespread view, antiferromagnetic fluctuations are the dominant ordering phenomenon in cuprates and Fe based superconductors and are responsible for electron pairing. In contrast, charge order is believed to be subdominant and compete with superconductivity. Here, we argue that fluctuating charge order in the (0,π) direction is a feature shared by the cuprates and the Fe based superconductors alike. Recent data and theoretical models suggest that superconductivity is brought about by charge order excitations independently from spin fluctuations. Thus, quantum fluctuations of charge order may provide an alternative to spin fluctuations as a mechanism of electron pairing in unconventional superconductors.

Persistent correlation between superconductivity and antiferromagnetic fluctuations near a nematic quantum critical point in FeSe1−xSx

“…Critical fluctuations of an ordered phase found in the proximity to unconventional superconductivity have frequently been discussed as a source of superconducting pairing [1][2][3][4]. In the iron-based superconductors [5,6], superconductivity (SC) is found in the vicinity of two types of long-range order: the stripe-type antiferromagnetic (AFM) order and the nematic order, which breaks the in-plane rotational symmetry while preserving time reversal symmetry.…”

Relationship Between Nematicity, Antiferromagnetic Fluctuations, and Superconductivity in FeSe1−xSx Revealed by NMR

“…Suppressing the transition temperatures of long-range orders with a tuning parameter has led to the discovery of superconductivity (SC) in the associated quantum phase transition (QPT) regions of several classes of materials such as heavy-Fermion systems [1][2][3], itinerant ferromagnets [4,5], high T c cuprates and Fe-based superconductors [3,6]. The quantum critical fluctuations of the suppressed long-range order parameter(s) could thus be responsible for the elusive Cooper pairing mechanism in those unconventional superconductors.…”