Incipient nematicity from electron flat bands in a kagome metal

Nathan Drucker; Thanh Nguyen; Manasi Mandal; Phum Siriviboon; Yujie Quan; Artittaya Boonkird; Ryotaro Okabe; Fankang Li; Kaleb Buragge; Fumiaki Funuma; Masaaki Matsuda; Douglas Abernathy; Travis Williams; Songxue Chi; Feng Ye; Christie Nelson; Bolin Liao; Pavel Volkov; Mingda Li

arXiv · 2401.17141

Incipient nematicity from electron flat bands in a kagome metal

Nathan Drucker·Thanh Nguyen·Manasi Mandal·Phum Siriviboon·Yujie Quan·Artittaya Boonkird·Ryotaro Okabe·Fankang Li·Kaleb Buragge·Fumiaki Funuma·Masaaki Matsuda·Douglas Abernathy·Travis Williams·Songxue Chi·Feng Ye·Christie Nelson·Bolin Liao·Pavel Volkov·Mingda Li

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Abstract

Engineering new quantum phases requires fine tuning of the electronic, orbital, spin, and lattice degrees of freedom. To this end, the kagome lattice with flat bands has garnered great attention by hosting various topological and correlated phases, when the flat band is at the Fermi level. Here we discover unconventional nematiciy in kagome metal CoSn, where flat bands are fully occupied below the Fermi level. Thermodynamic, dilatometry, resonant X-ray scattering, inelastic neutron scattering, Larmor diffraction, and thermoelectric measurements consistently hint at rotational symmetry-breaking and nematic order that is pronounced only near T=225 K. These observations, principally the nematic's finite temperature stability -- incipience -- can be explained by a phenomenological model which reveals that thermally excited flat bands promote symmetry breaking at a characteristic temperature. Our work shows that thermal fluctuations, which are typically detrimental for correlated electron phases, can induce new ordered states of matter, avoiding the requirements for fine tuning of electronic bands.

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Nathan Drucker, Thanh Nguyen, Manasi Mandal, Phum Siriviboon, Yujie Quan, Artittaya Boonkird, Ryotaro Okabe, Fankang Li, Kaleb Buragge, Fumiaki Funuma, Masaaki Matsuda, Douglas Abernathy, Travis Williams, Songxue Chi, Feng Ye, Christie Nelson, Bolin Liao, Pavel Volkov, Mingda Li. 2024-01-30. Incipient nematicity from electron flat bands in a kagome metal. https://arxiv.org/abs/2401.17141

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