Competition and/or Coexistence of Antiferromagnetism and Superconductivity in CeRhIn$_5$ and CeCoIn$_5$

TL;DR

This paper explores the complex interplay between antiferromagnetism and superconductivity in CeRhIn$_5$ and CeCoIn$_5$, revealing coexistence, phase transitions, and the influence of pressure and magnetic fields on their phase diagrams.

Contribution

It provides detailed phase diagrams and a new conceptual framework for understanding how magnetic order and superconductivity coexist and compete in these Ce compounds.

Findings

Coexistence of AF and SC in CeRhIn$_5$ below 2 GPa

Reinduction of AF by magnetic field above critical pressure

Emergence of a new high-field low-temperature phase in CeCoIn$_5$

Abstract

The Ce compounds CeCoIn$_5$ and CeRhIn$_5$ are ideal model systems to study the competition of antiferromagnetism (AF) and superconductivity (SC). Here we discuss the pressure--temperature and magnetic field phase diagrams of both compounds. In CeRhIn$_5$ the interesting observation is that in zero magnetic field a coexistence AF+SC phase exist inside the AF phase below the critical pressure $p_{\rm c}^\star \approx 2$ GPa. Above $p_{\rm c}^\star$ AF is suppressed in zero field but can be re-induced by applying a magnetic field. The collapse of AF under pressure coincides with the abrupt change of the Fermi surface. In CeCoIn$_5$ a new phase appears at low temperatures and high magnetic field (LTHF) which vanishes at the upper critical field $H_{\rm c2}$. In both compounds the paramagnetic pair breaking effect dominates at low temperature. We discuss the evolution of the upper critical field under high pressure of both compounds and propose a simple picture of the glue of reentrant magnetism to the upper critical field in order to explain the interplay of antiferromagnetic order and superconductivity.