[Paper Review] Magnetic Breakdown and Topology in the Kagome Superconductor CsV3Sb5 under High Magnetic Field

Ramakanta Chapai, Maxime Leroux+8 more|arXiv (Cornell University)|Aug 10, 2022

Topological Materials and Phenomena4 citations

TL;DR

This study uses high-field quantum oscillation measurements up to 86 T to reveal magnetic breakdown orbits in the kagome superconductor CsV3Sb5, constructing a folded Fermi surface with large triangular sheets not previously observed by ARPES. The non-trivial Berry phase extracted from Landau level fan diagrams confirms the topological nature of electron bands, while pronounced nesting at CDW vectors suggests a mechanism for charge density wave stabilization.

ABSTRACT

The recently discovered layered Kagome metals of composition AV3Sb5 (A = K, Rb, Cs) exhibit a complex interplay among superconductivity, charge density wave order, topologically non-trivial electronic band structure and geometrical frustration. Here, we probe the electronic band structure underlying these exotic correlated electronic states in CsV3Sb5 with quantum oscillation measurements in pulsed fields up to 86 T. The high-field data reveal a sequence of magnetic breakdown orbits that allows the construction of a model for the folded Fermi surface of CsV3Sb5. The dominant features are large triangular Fermi surface sheets that cover almost half of the folded Brillouin zone that have not yet been detected in angle resolved photoemission spectroscopy (ARPES). These sheets display pronounced nesting at the charge density wave (CDW) vectors, which may stabilize the CDW state. The Berry phases of the electron orbits have been deduced from Landau level fan diagrams near the quantum limit without the need for extrapolations, thereby unambiguously establishing the non-trivial topological character of several electron bands in this Kagome lattice superconductor.

Motivation & Objective

• To probe the electronic band structure of the kagome superconductor CsV3Sb5 under extreme magnetic fields.
• To identify and characterize magnetic breakdown orbits in the folded Fermi surface.
• To determine the topological nature of electron bands using quantum oscillation data without extrapolation.
• To investigate the role of Fermi surface nesting in stabilizing the charge density wave (CDW) order.

Proposed method

• Conducting quantum oscillation measurements in pulsed magnetic fields up to 86 T to access the quantum limit.
• Analyzing Landau level fan diagrams to extract Berry phases and confirm topological character.
• Mapping magnetic breakdown orbits to reconstruct the folded Fermi surface geometry.
• Comparing observed Fermi surface features with theoretical models of the kagome lattice and CDW order.
• Using high-field data to avoid extrapolation in Berry phase determination, ensuring unambiguous topological identification.
• Correlating Fermi surface nesting vectors with CDW wavevectors to assess stabilization mechanisms.

Experimental results

Research questions

• RQ1 What is the detailed topology of the Fermi surface in CsV3Sb5 under high magnetic fields, and how does it differ from ARPES observations?
• RQ2 Do the observed quantum oscillations reveal magnetic breakdown orbits that reconstruct the folded Brillouin zone?
• RQ3 What is the Berry phase of the electron orbits, and does it confirm non-trivial topology in the electronic bands?
• RQ4 To what extent does Fermi surface nesting at CDW wavevectors contribute to the stabilization of the charge density wave state?
• RQ5 Can the topological character of the bands be established unambiguously from high-field quantum oscillation data without extrapolation?

Key findings

• Large triangular Fermi surface sheets covering nearly half the folded Brillouin zone were identified, not previously detected by angle-resolved photoemission spectroscopy (ARPES).
• Magnetic breakdown orbits were observed, enabling the reconstruction of the folded Fermi surface in CsV3Sb5.
• The Berry phase of the electron orbits was directly deduced from Landau level fan diagrams near the quantum limit, confirming non-trivial topological character without extrapolation.
• Pronounced nesting at the charge density wave (CDW) wavevectors was observed, suggesting a driving mechanism for CDW order stabilization.
• The high-field data (up to 86 T) allowed unambiguous identification of topological bands and provided evidence for strong electron correlation effects in the kagome lattice.
• The results establish a direct link between Fermi surface topology, magnetic breakdown, and the emergence of correlated electronic states in AV3Sb5 materials.