biostudies-literatureGu YDOE | SC | Basic Energy Sciences (BES)DOE | SC | Basic Energy Sciences8104https://www.ebi.ac.uk/biostudies/studies/S-EPMC11405877biostudies-literatureUnknown15(1)The nodal-line semiconductor Mn₃Si₂Te₆ 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 Mn₃Si₂Te₆ 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.Nature communicationsUnconventional insulator-to-metal phase transition in Mn₃Si₂Te₆.PMC11405877DE-SC00023144Saha ALin LFDe CGu YOzerov MHaule KDagotto EHomes CWon CJZhang YMusfeldt JLSmith KACheong SWBirol TfalseUnconventional insulator-to-metal phase transition in Mn₃Si₂Te₆.The nodal-line semiconductor Mn₃Si₂Te₆ 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 Mn₃Si₂Te₆ 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.2024-01-01T00:00:00Z2024 Sep2025-04-18T13:07:38.56Z2025-04-06T22:40:45.168ZS-EPMC114058773928518510.1038/s41467-024-52350-1