Order-by-disorder charge density wave condensation at $\mathbf{\textit{q} =(\frac{1}{3},\frac{1}{3},\frac{1}{3})}$ in kagome metal ScV$_6$Sn$_6$
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arXiv
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| Natura: | Preprint |
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2023
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| _version_ | 1866914653734436864 |
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| author | Subedi, Alaska |
| author_facet | Subedi, Alaska |
| contents | The recent discovery of a charge density wave order at the wave vector $P$ $(\frac{1}{3},\frac{1}{3},\frac{1}{3})$ in the kagome metal ScV$_6$Sn$_6$ has created a mystery because subsequent theoretical and experimental studies show a dominant phonon instability instead at another wave vector $H$ $(\frac{1}{3},\frac{1}{3},\frac{1}{2})$. In this paper, I use first principles total energy calculations to map out the landscape of the structural distortions due to the unstable phonon modes at $H$, $L$ $(\frac{1}{2},0,\frac{1}{2})$, and $P$ present in this material. In agreement with previous results, I find that the distortions due to the $H$ instability cause the largest gain in energy relative to the parent structure, followed in order by the $L$ and $P$ instabilities. However, only two distinct structure occur due to this instability, which are separated by 6 meV/f.u. The instability at $L$ results in three distinct structures separated in energy by 5 meV/f.u. In contrast, six different distorted structures are stabilized due to the instability at $P$, and they all lie within 2 meV/f.u.\ of each other. Hence, despite a lower energy gain, the condensation at $P$ could be favorable due to a larger entropy gain associated with the fluctuations within a manifold with larger multiplicity via the order-by-disorder mechanism. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2308_11553 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Order-by-disorder charge density wave condensation at $\mathbf{\textit{q} =(\frac{1}{3},\frac{1}{3},\frac{1}{3})}$ in kagome metal ScV$_6$Sn$_6$ Subedi, Alaska Strongly Correlated Electrons Materials Science The recent discovery of a charge density wave order at the wave vector $P$ $(\frac{1}{3},\frac{1}{3},\frac{1}{3})$ in the kagome metal ScV$_6$Sn$_6$ has created a mystery because subsequent theoretical and experimental studies show a dominant phonon instability instead at another wave vector $H$ $(\frac{1}{3},\frac{1}{3},\frac{1}{2})$. In this paper, I use first principles total energy calculations to map out the landscape of the structural distortions due to the unstable phonon modes at $H$, $L$ $(\frac{1}{2},0,\frac{1}{2})$, and $P$ present in this material. In agreement with previous results, I find that the distortions due to the $H$ instability cause the largest gain in energy relative to the parent structure, followed in order by the $L$ and $P$ instabilities. However, only two distinct structure occur due to this instability, which are separated by 6 meV/f.u. The instability at $L$ results in three distinct structures separated in energy by 5 meV/f.u. In contrast, six different distorted structures are stabilized due to the instability at $P$, and they all lie within 2 meV/f.u.\ of each other. Hence, despite a lower energy gain, the condensation at $P$ could be favorable due to a larger entropy gain associated with the fluctuations within a manifold with larger multiplicity via the order-by-disorder mechanism. |
| title | Order-by-disorder charge density wave condensation at $\mathbf{\textit{q} =(\frac{1}{3},\frac{1}{3},\frac{1}{3})}$ in kagome metal ScV$_6$Sn$_6$ |
| topic | Strongly Correlated Electrons Materials Science |
| url | https://arxiv.org/abs/2308.11553 |