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.
@article{arxiv.2401.17141,
title = {Incipient nematicity from electron flat bands in a kagome metal},
author = {Nathan Drucker and Thanh Nguyen and Manasi Mandal and Phum Siriviboon and Yujie Quan and Artittaya Boonkird and Ryotaro Okabe and Fankang Li and Kaleb Buragge and Fumiaki Funuma and Masaaki Matsuda and Douglas Abernathy and Travis Williams and Songxue Chi and Feng Ye and Christie Nelson and Bolin Liao and Pavel Volkov and Mingda Li},
journal= {arXiv preprint arXiv:2401.17141},
year = {2024}
}
Comments
37 pages, 5 main figures, 14 supplementary figures