Observation of superparamagnetism in coexistence with quantum anomalous Hall C = ±1 and C = 0 Chern states
| Autor: | Ella Lachman, Y. Myasoedov, Yoshinori Tokura, Masashi Kawasaki, Martin E. Huber, Masataka Mogi, Yonathan Anahory, Eli Zeldov, Aviram Uri, Atsushi Tsukazaki, Jayanta Sarkar, K. Bagani |
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| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
Quantum anomalous Hall effect
FOS: Physical sciences 02 engineering and technology lcsh:Atomic physics. Constitution and properties of matter 01 natural sciences Quantization (physics) Condensed Matter::Materials Science Quantum state 0103 physical sciences Mesoscale and Nanoscale Physics (cond-mat.mes-hall) lcsh:TA401-492 010306 general physics Quantum Axion Physics Condensed Matter - Materials Science Condensed matter physics Condensed Matter - Mesoscale and Nanoscale Physics Doping Materials Science (cond-mat.mtrl-sci) 021001 nanoscience & nanotechnology Condensed Matter Physics Electronic Optical and Magnetic Materials lcsh:QC170-197 Condensed Matter - Other Condensed Matter Topological insulator lcsh:Materials of engineering and construction. Mechanics of materials 0210 nano-technology Superparamagnetism Other Condensed Matter (cond-mat.other) |
| Zdroj: | npj Quantum Materials, Vol 2, Iss 1, Pp 1-7 (2017) |
| ISSN: | 2397-4648 |
| Popis: | Simultaneous transport and scanning nanoSQUID-on-tip magnetic imaging studies in Cr-(Bi,Sb)$_2$Te$_3$ modulation-doped films reveal the presence of superparamagnetic order within the quantum anomalous Hall regime. In contrast to the expectation that a long-range ferromagnetic order is required for establishing the quantum anomalous Hall state, superparamagnetic dynamics of weakly interacting nanoscale magnetic islands is observed both in the plateau transition regions as well as within the fully quantized C=$\pm$1 Chern plateaus. Modulation doping of the topological insulator films is found to give rise to significantly larger superparamagnetic islands as compared to uniform magnetic doping, evidently leading to enhanced robustness of the quantum anomalous Hall effect. Nonetheless, even in this more robust quantum state, attaining full quantization of transport coefficients requires magnetic alignment of at least 95% of the superparamagnetic islands. The superparamagnetic order is also found within the incipient C=0 zero Hall plateau, which may host an axion state if the top and bottom magnetic layers are magnetized in opposite directions. In this regime, however, a significantly lower level of island alignment is found in our samples, hindering the formation of the axion state. Comprehension and control of superparamagnetic dynamics is thus a key factor in apprehending the fragility of the quantum anomalous Hall state and in enhancing the endurance of the different quantized states to higher temperatures for utilization of robust topological protection in novel devices. Comment: 17 pages, 3 figures |
| Databáze: | OpenAIRE |
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