Evidence of electronic instability driven structural distortion in the nodal line semimetal CoSn$_2$
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| Main Authors: | , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866914060976521216 |
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| author | Nandi, Suman Maity, Bishal Dan, Shovan Ali, Khadiza Patra, Bikash Mondal, Anshuman Garbarino, Gaston Rodière, Pierre Ramakrishnan, Sitaram Singh, Bahadur Thamizhavel, Arumugam |
| author_facet | Nandi, Suman Maity, Bishal Dan, Shovan Ali, Khadiza Patra, Bikash Mondal, Anshuman Garbarino, Gaston Rodière, Pierre Ramakrishnan, Sitaram Singh, Bahadur Thamizhavel, Arumugam |
| contents | Understanding the mechanisms that drive spontaneous rotational symmetry breaking in correlated electron systems is a central challenge in condensed matter physics. Although such symmetry breaking phases have been studied in low-dimensional and strongly correlated materials, its emergence in structurally simpler compounds remains less explored. Here, we investigate non-magnetic CoSn$_2$ that is a centrosymmetric intermetallic compound crystallizing in a tetragonal structure at ambient conditions, and discover an electronically driven symmetry breaking instability. Electrical resistivity reveals a distinct change in the slope below 25 K, deviating from the expected Bloch-Grüneisen behavior. This anomaly is attributed towards a structural change as at 22 K single crystal X-ray diffraction using synchrotron radiation uncovers weak superlattice reflections that leads to a doubling of $\textbf{a}$ and $\textbf{c}$, resulting in a 4-fold superstructure. The symmetry of the lattice reduces from tetragonal to acentric monoclinic but without any discernible monoclinic distortion down to 10 K. This structural transition is accompanied by a twofold symmetry in angular magnetoresistance, contrasting the fourfold symmetry observed at higher temperatures. First-principles calculations show no phonon softening but reveal enhanced electronic susceptibility, suggesting an electronic instability. Polarization-dependent ARPES measurements further identify a strong orbital anisotropy dominated by the in-plane Co-$d_{xy}$ states. Collectively, our results point to an electronic instability driven structural distortion in CoSn$_2$, offering a rare platform to study symmetry breaking in a non-magnetic metallic system. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2509_23221 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Evidence of electronic instability driven structural distortion in the nodal line semimetal CoSn$_2$ Nandi, Suman Maity, Bishal Dan, Shovan Ali, Khadiza Patra, Bikash Mondal, Anshuman Garbarino, Gaston Rodière, Pierre Ramakrishnan, Sitaram Singh, Bahadur Thamizhavel, Arumugam Materials Science Understanding the mechanisms that drive spontaneous rotational symmetry breaking in correlated electron systems is a central challenge in condensed matter physics. Although such symmetry breaking phases have been studied in low-dimensional and strongly correlated materials, its emergence in structurally simpler compounds remains less explored. Here, we investigate non-magnetic CoSn$_2$ that is a centrosymmetric intermetallic compound crystallizing in a tetragonal structure at ambient conditions, and discover an electronically driven symmetry breaking instability. Electrical resistivity reveals a distinct change in the slope below 25 K, deviating from the expected Bloch-Grüneisen behavior. This anomaly is attributed towards a structural change as at 22 K single crystal X-ray diffraction using synchrotron radiation uncovers weak superlattice reflections that leads to a doubling of $\textbf{a}$ and $\textbf{c}$, resulting in a 4-fold superstructure. The symmetry of the lattice reduces from tetragonal to acentric monoclinic but without any discernible monoclinic distortion down to 10 K. This structural transition is accompanied by a twofold symmetry in angular magnetoresistance, contrasting the fourfold symmetry observed at higher temperatures. First-principles calculations show no phonon softening but reveal enhanced electronic susceptibility, suggesting an electronic instability. Polarization-dependent ARPES measurements further identify a strong orbital anisotropy dominated by the in-plane Co-$d_{xy}$ states. Collectively, our results point to an electronic instability driven structural distortion in CoSn$_2$, offering a rare platform to study symmetry breaking in a non-magnetic metallic system. |
| title | Evidence of electronic instability driven structural distortion in the nodal line semimetal CoSn$_2$ |
| topic | Materials Science |
| url | https://arxiv.org/abs/2509.23221 |