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Imágenes del ferromagnetismo orbital en un aislante de Chern
C L Tschirhart1, M Serlin1, H Polshyn1
1Department of Physics, University of California, Santa Barbara, CA 93106, USA.
Science (New York, N.Y.)
|May 28, 2021
Resumen
Los investigadores observaron el magnetismo orbital en el grafeno de doble capa retorcido, lo que condujo a un efecto Hall anómalo cuantizado. Este magnetismo, principalmente orbital, forma dominios reproducibles vinculados a las imperfecciones estructurales.
Área de la Ciencia:
- Física de la materia condensada
- Ciencias de los materiales
- Los fenómenos cuánticos
Sus antecedentes:
- Los sistemas de banda plana de Moiré exhiben una ruptura de simetría de inversión de tiempo espontánea.
- Esta ruptura de simetría puede conducir al efecto Hall anómalo cuantizado (QAHE).
- Comprender la naturaleza y el origen del magnetismo en estos sistemas es crucial.
Objetivo del estudio:
- Para investigar las propiedades magnéticas del grafeno de doble capa retorcida (TBG) alineado con el nitruro de boro hexagonal (hBN).
- Para determinar la naturaleza (orbitales frente a espín) del magnetismo observado.
- Para explorar la relación entre el magnetismo, el QAHE y la estructura del material.
Principales métodos:
- Utilizó un dispositivo de interferencia cuántica superconductor (SQUID) para obtener imágenes de campos magnéticos errantes.
- Magnetización medida en las heteroestructuras TBG/hBN.
- Mapeado la evolución espacial de la inversión impulsada por el campo magnético.
Principales resultados:
- Se observó una magnetización significativa (varios magnetones de Bohr por portador de carga), lo que indica principalmente el magnetismo orbital.
- Encontramos un gran cambio en la magnetización cerca de la brecha QAHE, consistente con la teoría del aislante orbital de Chern.
- Se han identificado dominios magnéticos reproducibles a escala micrométrica relacionados con trastornos estructurales.
Conclusiones:
- El estudio confirma el magnetismo orbital como la fuente de QAHE en TBG/hBN.
- Los estados de borde quiral contribuyen a la magnetización, apoyando el modelo de aislante orbital de Chern.
- El desorden estructural juega un papel clave en fijar los dominios magnéticos e influir en la inversión magnética.
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