Magnetic field induced pattern of coexisting condensates in the superconducting state of CeCoIn$_5$

TL;DR

This paper reports the discovery of a novel high-field state in CeCoIn$_5$ where multiple condensates coexist in a patterned arrangement, challenging traditional views of homogeneous superconductivity and suggesting new avenues for exploring exotic states.

Contribution

It introduces a new type of exotic state with coexisting condensates in CeCoIn$_5$, expanding understanding of inhomogeneous superconducting phases beyond the FFLO model.

Findings

Observation of a patterned coexistence of condensates in CeCoIn$_5$

Identification of a state including d-wave SC, $\pi$-triplet SC, and SDW

Proposed a generic mechanism for inhomogeneous condensate formation

Abstract

In usual superconductors the carriers form Cooper pairs that have zero total momentum meaning that the superfluid density is homogeneous. We know for decades that it is a priori possible to observe at high fields the Fulde-Ferrel-Larkin-Ovchinikov (FFLO) state in which the superfluid density exhibits a field dependent modulation. The search for such inhomogeneous condensates in materials is the subject of tremendous excitement especially after the discovery of a promising high-field superconducting (HFSC) phase in CeCoIn$_5$. However, subsequent neutron and NMR experiments contradicted the FFLO picture in CeCoIn$_5$ establishing a puzzling coupling of the distinct HFSC state with a magnetic modulation. Here we show that, a novel type of exotic state is observed at high fields in CeCoIn$_5$ in which a pattern of coexisting condensates manifests. The specific pattern includes the d-wave singlet SC state, the staggered $\pi$-triplet SC state and Spin Density Waves (SDW). Because of particle-hole asymmetry these three condensates may either appear separately or all three together providing a new perspective on antiferromagnetic superconductors that may include high-$T_c$ cuprates and pniktides. The field induced transition to the pattern state in CeCoIn$_5$ is only a paradigm of a generic mechanism that prevents the elimination of the dominating condensate by the field via the formation of a pattern of condensates. This opens new avenues for the search of exotic states not only in electronic systems, but also in other systems where inhomogeneous condensates are actively discussed like trapped atomic fermi gases and dense quark matter.