[Paper Review] Reemergeing electronic nematicity in heavily hole-doped Fe-based superconductors

J. Li, Dan Zhao+9 more|arXiv (Cornell University)|Nov 15, 2016

Iron-based superconductors research24 references16 citations

TL;DR

This study demonstrates the reemergence of electronic nematicity in heavily hole-doped Fe-based superconductors, specifically CsFe2As2, using nuclear magnetic resonance (NMR) measurements. It reveals anisotropic quadrupolar broadening indicating local rotational symmetry breaking, establishing a direct link between the Mott insulating phase and electronic nematicity, thereby supporting a universal mechanism for nematicity in high-temperature superconductors.

ABSTRACT

In correlated electrons system, quantum melting of electronic crystalline phase often gives rise to many novel electronic phases. In cuprates superconductors, melting the Mott insulating phase with carrier doping leads to a quantum version of liquid crystal phase, the electronic nematicity, which breaks the rotational symmetry and exhibits a tight twist with high-temperature superconductivity. Recently, the electronic nematicity has also been observed in Fe-based superconductors. However, whether it shares a similar scenario with its cuprates counterpart is still elusive. Here, by measuring nuclear magnetic resonance in CsFe2As2, a prototypical Fe-based superconductor perceived to have evolved from a Mott insulating phase at 3d5 configuration, we report anisotropic quadruple broadening effect as a direct result of local rotational symmetry breaking. For the first time, clear connection between the Mott insulating phase and the electronic nematicity can be established and generalized to the Fe-based superconductors. This finding would promote a universal understanding on electronic nematicity and its relation with high-temperature superconductivity.

Motivation & Objective

• To investigate the origin of electronic nematicity in Fe-based superconductors, particularly in systems with strong electron correlation.
• To determine whether electronic nematicity in Fe-based superconductors arises from a quantum melting of a Mott insulating phase, analogous to cuprates.
• To establish a direct experimental connection between the Mott insulating state and the emergence of nematic order in heavily hole-doped systems.
• To explore the universality of electronic nematicity in correlated electron systems, especially in relation to high-temperature superconductivity.

Proposed method

• Nuclear magnetic resonance (NMR) measurements were performed on CsFe2As2, a prototypical Fe-based superconductor with a 3d5 configuration.
• The study focused on quadrupolar broadening of the 57Fe NMR spectra to probe local electronic symmetry breaking.
• Anisotropic quadrupolar broadening was analyzed to detect broken rotational symmetry at the Fe site.
• The data were interpreted in the context of a Mott insulating parent phase, with hole doping driving the system into a nematic state.
• The analysis compared the observed nematic response to theoretical expectations for quantum phase transitions in correlated systems.

Experimental results

Research questions

• RQ1 Does electronic nematicity reemerge in heavily hole-doped Fe-based superconductors such as CsFe2As2?
• RQ2 Is there a direct experimental link between the Mott insulating phase and the emergence of electronic nematicity in Fe-based systems?
• RQ3 Does the nematic order in Fe-based superconductors arise via a mechanism analogous to that in cuprates, involving quantum melting of a Mott insulator?
• RQ4 How does the local electronic symmetry breaking manifest in the NMR spectra of hole-doped FeAs-based compounds?

Key findings

• Anisotropic quadrupolar broadening in 57Fe NMR spectra of CsFe2As2 provides direct evidence of local rotational symmetry breaking, signaling electronic nematicity.
• The nematic order reemerges in the heavily hole-doped regime, indicating a non-monotonic evolution of nematicity with doping.
• The observed nematicity is directly linked to the parent Mott insulating phase, suggesting a universal origin in correlated electron systems.
• The results support a scenario where electronic nematicity in Fe-based superconductors arises from quantum melting of a Mott insulator, similar to cuprates.