Unconventional insulator-to-metal phase transition in Mn3Si2Te6

• Published in: Nature communications Vol. 15; no. 1; pp. 8104 - 6
• Main Authors: Gu, Yanhong, Smith, Kevin A., Saha, Amartyajyoti, De, Chandan, Won, Choong-jae, Zhang, Yang, Lin, Ling-Fang, Cheong, Sang-Wook, Haule, Kristjan, Ozerov, Mykhaylo, Birol, Turan, Homes, Christopher, Dagotto, Elbio, Musfeldt, Janice L.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 16-09-2024; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/119/2795; 639/301/119/995; Colossal magnetoresistance; Current carriers; Electron spin; electronic properties and materials; Frequency dependence; Humanities and Social Sciences; Infrared signatures; Inhomogeneity; Jahn-Teller effect; Magnetoresistivity; MATERIALS SCIENCE; Metals; multidisciplinary; Percolation; Phase separation; Phase transitions; phase transitions and critical phenomena; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-52350-1

The nodal-line semiconductor Mn
3
Si
2
Te
6
is generating enormous excitment due to the recent discovery of a field-driven insulator-to-metal transition and associated colossal magnetoresistance as well as evidence for a new type of quantum state involving chiral orbital currents. Strikingly, these qualities persist even in the absence of traditional Jahn-Teller distortions and double-exchange mechanisms, raising questions about exactly how and why magnetoresistance occurs along with conjecture as to the likely signatures of loop currents. Here, we measured the infrared response of Mn
3
Si
2
Te
6
across the magnetic ordering and field-induced insulator-to-metal transitions in order to explore colossal magnetoresistance in the absence of Jahn-Teller and double-exchange interactions. Rather than a traditional metal with screened phonons, the field-driven insulator-to-metal transition leads to a weakly metallic state with localized carriers. Our spectral data are fit by a percolation model, providing evidence for electronic inhomogeneity and phase separation. Modeling also reveals a frequency-dependent threshold field for carriers contributing to colossal magnetoresistance which we discuss in terms of polaron formation, chiral orbital currents, and short-range spin fluctuations. These findings enhance the understanding of insulator-to-metal transitions in new settings and open the door to the design of unconventional colossal magnetoresistant materials.
Field-driven insulator-to-metal transition and associated colossal magnetoresistance have been reported in the magnetic nodal-line semiconductor Mn
3
Si
2
Te
6
. Gu et al. measure infrared response across magnetic ordering and the transition, revealing a weakly metallic state instead of a traditional metallic state.