Coexistence of near-EF flat band and van Hove singularity in a two-phase superconductor

Abstract

In quantum many-body systems, particularly, the ones with large near-EF density states, like flat bands or van Hove singularity (VHS), electron correlations often give rise to rich phase diagrams with multiple coexisting/competing orders occurring at similar energy scales. The recently discovered locally noncentrosymmetric heavy fermion superconductor CeRh2As2 has stimulated extensive attention due to its unusual H-T phase diagram, consisting of two-phase superconductivity, antiferromagnetic order, and possible quadrupole-density wave orders. However, despite its great importance, the near-EF electronic structure remains experimentally elusive. Here, we provide this key information by combining soft X-ray and vacuum ultraviolet (VUV) angle-resolved photoemission spectroscopy measurements and atom-resolved DFT+U calculations. With bulk-sensitive soft X-rays, we reveal quasi-2D hole- and 3D electron- pockets with a pronounced nesting feature. Most importantly, we observe a symmetry-protected fourfold VHS coexisting with the Ce 4f flat bands near the EF, which, to the best of our knowledge, has never been reported before. Such a rare coexistence is expected to lead to a large density of states at the zone edge, enhancement in electron correlations, and a large upper critical field of the odd-parity superconducting phase. Uniquely, it will also result in a new type of f-VHS hybridization that alters the order and fine electronic structure of the symmetry-protected VHS and flat bands. These peculiarities offer important dimensions for understanding the reported rich phase diagram and are discussed as an origin of superconductivity with two phases. Our findings not only provide key insights into the nature of multiple phases in CeRh${}_2$As${}_2$, but also open up new prospects for exploring the novelties of many-body systems with f-VHS hybridization.

A version of the original submission (submitted in July)

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Cited by in corpus (19)

• Fermi Surface Nesting with Heavy Quasiparticles in the Locally Noncentrosymmetric Superconductor CeRh${}_2$As${}_2$
• Exploring Fermi Surface Nesting and the Nature of Heavy Quasiparticles in the Spin-Triplet Superconductor Candidate CeRh${}_2$As${}_2$
• Correlation-induced Fermi surface evolution and topological crystalline superconductivity in CeRh2As2
• Coexistence of local magnetism and superconductivity in the heavy-fermion CeRh${}_2$As${}_2$ revealed by $\mu$SR studies
• Exposing the odd-parity superconductivity in CeRh${}_2$As${}_2$ with hydrostatic pressure
• Origin of the non-Fermi-liquid behavior in CeRh2As2
• Unified picture of superconductivity and magnetism in CeRh${}_2$As${}_2$
• Inversion-asymmetric itinerant antiferromagnets by the space group symmetry
• Field-induced superconductivity mediated by odd-parity multipole fluctuation
• Superconducting meron phase in locally noncentrosymmetric superconductors
• Incommensuration in odd-parity antiferromagnets
• Unveiling the superconducting scenario in multiphase superconductor CeRh${}_2$As${}_2$ from space-group symmetry analysis and DFT calculations
• Strain Engineering of van Hove Singularity and Coupled Itinerant Ferromagnetism in Quasi-2D Oxide Superlattices
• Quantum geometric magnetic monopole and two-phase superconductivity in CeRh${}_2$As${}_2$
• Multipolar fluctuations from localized 4f electrons in CeRh2As2
• Dimensionality tuning of heavy-fermion states in ultrathin CeSi2 films
• Composite Superconducting Orders and Magnetism in CeRh${}_2$As${}_2$
• Quasiclassical theory of vortex states in locally non-centrosymmetric superconductors: application to CeRh${}_2$As${}_2$
• La substitution studies on the heavy-fermion superconductor CeRh${}_2$As${}_2$