Origin of competing charge density waves in kagome metal ScV<sub>6</sub>Sn<sub>6</sub>.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 39616157.
- Also identified by DOI 10.1038/s41467-024-54702-3 and PMC identifier 11608277.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Understanding competing charge density wave (CDW) orders in the bilayer kagome metal ScV<sub>6</sub>Sn<sub>6</sub> remains challenging. Experimentally, upon cooling, short-range order with wave vector <math xmlns="http://www.w3.org/1998/Math/MathML"> <msub><mrow><mi>q</mi></mrow> <mrow><mn>2</mn></mrow> </msub> <mo>=</mo> <mrow><mo>(</mo> <mrow> <mfrac><mrow><mn>1</mn></mrow> <mrow><mn>3</mn></mrow> </mfrac> <mo>,</mo> <mfrac><mrow><mn>1</mn></mrow> <mrow><mn>3</mn></mrow> </mfrac> <mo>,</mo> <mfrac><mrow><mn>1</mn></mrow> <mrow><mn>2</mn></mrow> </mfrac> </mrow> <mo>)</mo></mrow> </math> forms, which is subsequently suppressed by the condensation of long-range <math xmlns="http://www.w3.org/1998/Math/MathML"> <msub><mrow><mi>q</mi></mrow> <mrow><mn>3</mn></mrow> </msub> <mo>=</mo> <mrow><mo>(</mo> <mrow> <mfrac><mrow><mn>1</mn></mrow> <mrow><mn>3</mn></mrow> </mfrac> <mo>,</mo> <mfrac><mrow><mn>1</mn></mrow> <mrow><mn>3</mn></mrow> </mfrac> <mo>,</mo> <mfrac><mrow><mn>1</mn></mrow> <mrow><mn>3</mn></mrow> </mfrac> </mrow> <mo>)</mo></mrow> </math> CDW order at lower temperature. Theoretically, however, the q<sub>2</sub> CDW is predicted as the ground state, leaving the CDW mechanism elusive. Here, using anharmonic phonon-phonon calculations combined with density functional theory, we predict a temperature-driven structural phase transitions from the high-temperature pristine phase to the q<sub>2</sub> CDW, followed by the low-temperature q<sub>3</sub> CDW, explaining experimental observations. We demonstrate that semi-core electron states stabilize the q<sub>3</sub> CDW over the q<sub>2</sub> CDW. Furthermore, we find that the out-of-plane lattice parameter controls the competing CDWs, motivating us to propose compressive bi-axial strain as an experimental protocol to stabilize the q<sub>2</sub> CDW. Finally, we suggest Ge or Pb doping at the Sn site as another potential avenue to control CDW instabilities. Our work provides a full theory of CDWs in ScV<sub>6</sub>Sn<sub>6</sub>, rationalizing experimental observations and resolving earlier discrepancies between theory and experiment.