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Filling-Resolved Symmetry-Weighted Order Graph for Correlated Phase Selection in Monolayer Kagome Metals \(A\mathrm{V}_{3}\mathrm{Sb}_{5}\)

John B. Goodenough1, Simon Weinstock1
1Carnegie Mellon Software Engineering Institute
John B. Goodenough
Carnegie Mellon Software Engineering Institute
Simon Weinstock
Carnegie Mellon Software Engineering Institute

Abstract

Monolayer kagome metals \(A\mathrm{V}_{3}\mathrm{Sb}_{5}\) (\(A=\mathrm{K},\mathrm{Rb},\mathrm{Cs}\)) form a problem of materials design under reduced symmetry, with van Hove singularities nearby, charge order, competing superconducting phases, and Hall-sensitivity within a limited energy interval accessible to strain, gate, and stoichiometric tuning. The question raised in the present paper concerns not whether correlated phases arise in monolayer \(A\mathrm{V}_{3}\mathrm{Sb}_{5}\) but which one should be investigated in the first place, given a particular Fermi level and tuning strategy. For answering that, we develop a symmetry-based order graph whose nodes comprise a type-II filling regime around \(-6~\mathrm{meV}\), a type-I filling regime centered on \(9~\mathrm{meV}\), a positive-filling region near \(35~\mathrm{meV}\), six charge-order channels, two main superconducting channels with even parity, and experimental tools. The edge weights incorporate proximity to van Hoves, \(M\)-point commensurability, local/nearest-neighbor interaction preference, time-reversal symmetry consideration, and monolayer access. A different hierarchy emerges for each channel. The type-II quartet channel favors rectangular inverse star of David and star of David doublet ordering, while maintaining \(A_g\) superconducting order as the strongest competitor. The type-I channel accommodates a more symmetric, commensurate charge order through a wide susceptibility peak contribution. A separation of the Hall-active \(\mathrm{TRSB}\)-2 phase from \(B_{1g}\) superconducting order by the positive-filling channel makes anomalous Hall measurements and pairing-symmetry checks a crucial experimental task. Stability normalization in terms of cohesive energy, the \(4~\mathrm{meV}\) per atom distortion limit, and the exfoliation energy of \(42\), \(45\), and \(45~\mathrm{meV}/\text{\AA}^{2}\) for \(A=\mathrm{K}\), Rb, and Cs leads to \(\mathrm{KV}_{3}\mathrm{Sb}_{5}\) as the optimal choice for a first target monolayer sample, although \(\mathrm{RbV}_{3}\mathrm{Sb}_{5}\) and \(\mathrm{CsV}_{3}\mathrm{Sb}_{5}\) samples are important comparative benchmarks.

Keywords: kagome metal, monolayer \(A\mathrm{V}_{3}\mathrm{Sb}_{5}\), charge density wave, superconductivity, van Hove singularity, two-dimensional materials, anomalous Hall response
Copyright © 2023 John B. Goodenough, Simon Weinstock. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.