TY - JOUR
T1 - Electronic transport across the insulator-metal transition in Co-doped pyrite FeS2 single crystals
AU - Das, Bhaskar
AU - Voigt, Bryan
AU - Moore, William
AU - Lee, Yeon
AU - Maiti, Moumita
AU - Chaturvedi, Vipul
AU - Haugstad, Greg
AU - Manno, Michael
AU - Aydil, Eray
AU - Leighton, Chris
N1 - Publisher Copyright:
© 2025 American Physical Society.
PY - 2025/5
Y1 - 2025/5
N2 - Pyrite FeS2 is a low-cost, sustainable, nontoxic, ∼1-eV-band gap semiconductor with unrealized potential in several application arenas, including photovoltaics. From the fundamental perspective, issues such as surface conduction and the deep-donor nature of S vacancies have hindered the study of low-temperature electronic phenomena in pyrite, including the insulator-metal transition (IMT). Here, we leverage a recently developed CoS2-based contact scheme in tandem with wide-range doping via shallow Co donors to directly access low-temperature bulk FeS2 transport properties and thus probe the IMT. Thoroughly characterized FeS2:Co single crystals are studied over broad ranges of temperature (0.4-400 K) and Hall electron density (8.6×1016-2.0×1020cm-3) through resistivity, Hall effect, and magnetoresistance measurements. The IMT is found to occur near 2×1017cm-3, with Efros-Shklovskii variable-range hopping below this, weak-localization-corrected metallic conductivity above this, and the onset of magnetic effects at the highest doping levels. Most significantly, unexpected additional phenomena are found near the IMT, including a nonlinear Hall effect with nonmonotonic temperature and doping dependence, and a nonsaturating, linear positive magnetoresistance at low temperatures. Quantitative analysis points to unusually strong disorder effects in the vicinity of the IMT, further elucidating the electronic behavior of this unique semiconductor.
AB - Pyrite FeS2 is a low-cost, sustainable, nontoxic, ∼1-eV-band gap semiconductor with unrealized potential in several application arenas, including photovoltaics. From the fundamental perspective, issues such as surface conduction and the deep-donor nature of S vacancies have hindered the study of low-temperature electronic phenomena in pyrite, including the insulator-metal transition (IMT). Here, we leverage a recently developed CoS2-based contact scheme in tandem with wide-range doping via shallow Co donors to directly access low-temperature bulk FeS2 transport properties and thus probe the IMT. Thoroughly characterized FeS2:Co single crystals are studied over broad ranges of temperature (0.4-400 K) and Hall electron density (8.6×1016-2.0×1020cm-3) through resistivity, Hall effect, and magnetoresistance measurements. The IMT is found to occur near 2×1017cm-3, with Efros-Shklovskii variable-range hopping below this, weak-localization-corrected metallic conductivity above this, and the onset of magnetic effects at the highest doping levels. Most significantly, unexpected additional phenomena are found near the IMT, including a nonlinear Hall effect with nonmonotonic temperature and doping dependence, and a nonsaturating, linear positive magnetoresistance at low temperatures. Quantitative analysis points to unusually strong disorder effects in the vicinity of the IMT, further elucidating the electronic behavior of this unique semiconductor.
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U2 - 10.1103/PhysRevMaterials.9.054601
DO - 10.1103/PhysRevMaterials.9.054601
M3 - Article
AN - SCOPUS:105004695590
SN - 2475-9953
VL - 9
JO - Physical Review Materials
JF - Physical Review Materials
IS - 5
M1 - 054601
ER -