Theory of the charge density wave in A V3 Sb5 kagome metals

Journal Article · Mon Dec 27 04:00:00 EST 2021 · Physical Review. B

DOI:https://doi.org/10.1103/physrevb.104.214513· OSTI ID:1979685

Christensen, Morten H. ^[1]; Birol, Turan ^[2]; Andersen, Brian M. ^[3]; Fernandes, Rafael M. ^[2]

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1. Copenhagen Univ. (Denmark); OSTI
2. Univ. of Minnesota, Minneapolis, MN (United States)
3. Copenhagen Univ. (Denmark)

The family of metallic kagome compounds AV₃Sb₅ (A = K, Rb, Cs) was recently discovered to exhibit both superconductivity and charge order. The nature of the charge density wave (CDW) phase is presently unsettled, which complicates the interpretation of the superconducting ground state. In this paper, we use group theory and density functional theory (DFT) to derive and solve a phenomenological Landau model for this CDW state. The DFT results reveal three unstable phonon modes with the same in-plane momentum but different out-of-plane momenta, whose frequencies depend strongly on the electronic temperature. This is indicative of an electronically driven CDW, stabilized by features of the in-plane electronic dispersion. Motivated by the DFT analysis, we construct a Landau free-energy expansion for coupled CDW order parameters with wave vectors at the M and L points of the hexagonal Brillouin zone. We find an unusual trilinear term coupling these different order parameters, which can promote the simultaneous condensation of both CDWs even if the two modes are not nearly degenerate. We classify the different types of coupled multi-Q CDW orders, focusing on those that break the sixfold rotational symmetry and lead to a unit-cell doubling along all three crystallographic directions, as suggested by experiments. Here, we determine a region in parameter space, characterized by large nonlinear Landau coefficients, where these phases—dubbed staggered trihexagonal and staggered Star of David—are the leading instabilities of the system. Finally, we discuss the implications of our results for the kagome metals.

• Research Organization: Univ. of Minnesota, Minneapolis, MN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE); National Science Foundation (NSF); Independent Research Fund Denmark
• Grant/Contract Number: SC0020045
• OSTI ID: 1979685
• Journal Information: Physical Review. B, Journal Name: Physical Review. B Journal Issue: 21 Vol. 104; ISSN 2469-9950
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
charge density waves
density functional calculations
group theory
kagome lattice
materials science
physics
superconductors