Charge ordering in the electron-doped superconductor Nd2-xCexCuO4 (1410.2253v1)

Abstract: In cuprate high-temperature superconductors, an antiferromagnetic Mott insulating state can be destabilized toward unconventional superconductivity by either hole- or electron-doping. In addition to these two electronic phases there is now a copious amount of evidence that supports the presence of a charge ordering (CO) instability competing with superconductivity inside the pseudogap state of the hole-doped (p-type) cuprates, but so far there has been no evidence of a similar CO in their electron-doped (n-type) counterparts. Here we report resonant x-ray scattering (RXS) measurements which demonstrate the presence of charge ordering in the n-type cuprate Nd2-xCexCuO4 near optimal doping. Remarkably we find that the CO in Nd2-xCexCuO4 occurs with similar periodicity, and along the same direction, as the CO in p-type cuprates. However, in contrast to the latter, the CO onset in Nd2-xCexCuO4 is higher than the pseudogap temperature, and is actually in the same temperature range where antiferromagnetic fluctuations are first detected -- thereby showing that CO and antiferromagnetic fluctuations are likely coupled in n-type cuprates. Overall our discovery uncovers a missing piece of the cuprate phase diagram and opens a parallel path to the study of CO and its relationship to other phenomena, such as antiferromagnetism (AF) and high-temperature superconductivity.

Charge Ordering in Electron-Doped Nd Cuprates

The paper investigates charge ordering (CO) phenomena in the electron-doped cuprate superconductor Nd, contributing important findings to the understanding of high-temperature superconductivity (HTS) in cuprate materials. Through resonant x-ray scattering (RXS) measurements, the paper identifies the existence of charge ordering in electron-doped (n-type) cuprates, a phenomenon previously well-documented in hole-doped (p-type) counterparts but elusive in n-type systems. This discovery marks a significant step towards a comprehensive understanding of the cuprate phase diagram.

Overview of Findings

The authors conduct meticulous resonant x-ray scattering experiments which reveal charge ordering in Nd near optimal doping levels. They report that CO in Nd exhibits similar periodicity and directional characteristics to the CO observed in p-type cuprates. However, a critical difference is noted: the charge ordering onset temperature in Nd exceeds the pseudogap temperature, diverging from the behavior observed in p-type systems where CO typically emerges concomitantly or subsequent to pseudogap formation.

A key observation from the paper is the coupling between charge ordering and antiferromagnetic (AF) fluctuations in n-type cuprates. This coupling suggests a potential interplay between CO and AF phenomena that might influence superconductivity in these materials, thereby unveiling new pathways for theoretical exploration.

Implications for Superconductivity

The discovery of CO in electron-doped cuprates adds a new dimension to the paper of superconductivity in cuprates, broadening the scope of known competing phases. Charge ordering represents a significant point of interaction in the superconducting phase diagram and presents a challenge in understanding its relationship with the pseudogap and AF correlations.

This interplay between CO and AF correlations may provide insights into the superconducting pairing mechanism in cuprates, contributing a piece to the puzzle of unconventional superconductivity. By bridging behaviors across electron- and hole-doped cuprates, the paper enhances the universality of charge order phenomena and opens new avenues for research into the relationship between electronic phase states and HTS.

Future Directions

The paper suggests several avenues for future research in AI and materials science. Investigations involving a broader range of doping levels and advanced computational simulations could deepen understanding of this phenomenon's impact on the cuprate phase diagram. Exploring the intrinsic electron-hole asymmetry in CO and AF interactions may yield insights into fundamental electronic properties across diverse superconducting materials.

In terms of AI applications, leveraging machine learning techniques to analyze vast datasets from x-ray scattering experiments could further elucidate patterns and relationships between CO, AF fluctuations, and superconductivity. AI-driven models could enhance predictive capabilities for material behavior under varied experimental conditions, thereby accelerating discovery and characterization efforts in condensed matter physics.

This valuable contribution calls for further exploration of charge order influences in electron-doped systems, potentially extending beyond cuprates to a broader set of unconventional superconductors. By delineating pathways and identifying key interactions, research inspired by these findings could achieve significant leaps in our understanding of high-temperature superconductivity and its practical applications.