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arXiv · 1904.13363

Possible Topological Phase Transition in Fe-Vacancy-Ordered $β$-Fe$_{4+δ}$Se$_{5}$ Nanowires

Keng-Yu Yeh·Tung-Sheng Lo·Chung-Chieh Chang·Phillip Wu·Kuei-Shu Chang-Liao·Ming-Jye Wang·Maw-Kuen Wu
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Abstract

We studied the electrical transport on $β$-Fe$_{4+δ}$Se$_{5}$ single-crystal nanowires, exhibiting $\sqrt{5}\times\sqrt{5}$ Fe-vacancy order and mixed valence of Fe. We observed a first-order metal-insulator transition of the transition temperature at $\sim$28~K at zero magnetic field. The dielectric relaxation reveals that the transition is related to an energy gap expansion of $\sim$12~meV, involving the charge-orbital ordering. At nearly 28~K, colossal positive magnetoresistance emerges, resulting from the magnetic-field dependent shift of the transition temperature. Through the transition, the magnetotransport behavior transits from two-dimension-like to one-dimension-like conduction. The transition temperature demonstrates anisotropy with the $c$-axis as the preferred orientation in magnetic fields, suggesting the spin-orbital coupling. Our findings demonstrate the novel magnetoresistive transition intimating a topological transition in the Fe-vacancy-ordered $β$-Fe$_{4+δ}$Se$_{5}$ nanowires. The results provide valuable information to better understand the orbital nature and the emergence of superconductivity in FeSe-based materials.

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Keng-Yu Yeh, Tung-Sheng Lo, Chung-Chieh Chang, Phillip Wu, Kuei-Shu Chang-Liao, Ming-Jye Wang, Maw-Kuen Wu. 2019-04-30. Possible Topological Phase Transition in Fe-Vacancy-Ordered $β$-Fe$_{4+δ}$Se$_{5}$ Nanowires. https://arxiv.org/abs/1904.13363

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