Multiple superconducting phases in heavy-fermion metals

Abstract

Symmetry breaking beyond a global U(1) phase is the key signature of unconventional superconductors. As prototypical strongly correlated materials, heavy-fermion metals provide ideal platforms for realizing unconventional superconductivity. In this article, we review heavy-fermion superconductivity, with a focus on those materials with multiple superconducting phases. In this context, we highlight the role of orbital-selective (matrix) pairing functions, which are defined as matrices in the space of effective orbital degrees of freedom such as electronic orbitals and sublattices as well as equivalent descriptions in terms of intra- and inter-band pairing components in the band basis. The role of quantum criticality and the associated strange-metal physics in the development of unconventional superconductivity is emphasized throughout. We discuss in some detail the recent experimental observations and theoretical perspectives in the illustrative cases of UTe2, CeRh2As2, and CeCu2Si2, where applied magnetic fields or pressure induce a variety of superconducting phases. We close by providing a brief overview of overarching issues and implications for possible future directions.

33 pages, 8 figures; To be published in Frontiers in Electronic Materials

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Cited by in corpus (7)

• A review of UTe${}_2$ at high magnetic fields
• Spectroscopic evidence of Kondo-induced quasi-quartet in CeRh${}_2$As${}_2$
• Coexistence of local magnetism and superconductivity in the heavy-fermion CeRh${}_2$As${}_2$ revealed by $\mu$SR studies
• Interior structure of the holographic s + p superconductor and chaotic-stable transition near the black hole singularity
• Pair-Kondo effect: a mechanism for time-reversal broken superconductivity in UTe${}_2$
• Phase evolution of Ce-based heavy-fermion superconductors under compression: a combined first-principle and effective-model study
• Near-flat-band-driven violation of Pauli limit in heavy fermion superconductors