• Buhot, Jonathan

Abstract

<jats:p>We report on an emerging symmetry axis in the magnetoresistance of bulk single crystals of quasi–one-dimensional Li<jats:sub>0.9</jats:sub>Mo<jats:sub>6</jats:sub>O<jats:sub>17</jats:sub> below <jats:italic>T</jats:italic><jats:sub>min</jats:sub> = 25 K, the temperature at which the electrical resistivity experiences a minimum. Detailed angle-dependent magnetoresistance sweeps reveal that this symmetry axis is induced by the development of a negative magnetoresistance, which is suppressed only for magnetic fields oriented along the poles of the MoO<jats:sub>6</jats:sub> octahedra that form the conducting chains. We show that this unusual negative magnetoresistance is consistent with the melting of dark excitons, composed of previously omitted orbitals within the <jats:italic>t</jats:italic><jats:sub>2g</jats:sub> manifold that order below <jats:italic>T</jats:italic><jats:sub>min</jats:sub>. The unveiled symmetry axis in directional magnetic fields not only provides evidence for the crystallization of these dark excitons but also sheds new light on the long-standing mystery of the metal-insulator transition in Li<jats:sub>0.9</jats:sub>Mo<jats:sub>6</jats:sub>O<jats:sub>17</jats:sub>.</jats:p>

Topics

• impedance spectroscopy
• single crystal
• resistivity
• crystallization
• one-dimensional