Competing charge-density wave instabilities in the kagome metal ScV6Sn6
Saizheng Cao, Chenchao Xu, Hiroshi Fukui, Taishun Manjo, Ying Dong, M. Shi, Yang Liu, Chao Cao, Yu Song
Abstract
Abstract Owing to its unique geometry, the kagome lattice hosts various many-body quantum states including frustrated magnetism, superconductivity, and charge-density waves (CDWs). In this work, using inelastic X-ray scattering, we discover a dynamic short-range $$\sqrt{3}\times \sqrt{3}\times 2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msqrt> <mml:mo>×</mml:mo> <mml:msqrt> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msqrt> <mml:mo>×</mml:mo> <mml:mn>2</mml:mn> </mml:math> CDW that is dominant in the kagome metal ScV 6 Sn 6 above T CDW ≈ 91 K, competing with the $$\sqrt{3}\times \sqrt{3}\times 3$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msqrt> <mml:mo>×</mml:mo> <mml:msqrt> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msqrt> <mml:mo>×</mml:mo> <mml:mn>3</mml:mn> </mml:math> CDW that orders below T CDW . The competing CDW instabilities lead to an unusual CDW formation process, with the most pronounced phonon softening and the static CDW occurring at different wavevectors. First-principles calculations indicate that the $$\sqrt{3}\times \sqrt{3}\times 2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msqrt> <mml:mo>×</mml:mo> <mml:msqrt> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msqrt> <mml:mo>×</mml:mo> <mml:mn>2</mml:mn> </mml:math> CDW is energetically favored, while a wavevector-dependent electron-phonon coupling (EPC) promotes the $$\sqrt{3}\times \sqrt{3}\times 3$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msqrt> <mml:mo>×</mml:mo> <mml:msqrt> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msqrt> <mml:mo>×</mml:mo> <mml:mn>3</mml:mn> </mml:math> CDW as the ground state, and leads to enhanced electron scattering above T CDW . These findings underscore EPC-driven correlated many-body physics in ScV 6 Sn 6 and motivate studies of emergent quantum phases in the strong EPC regime.