- Award ID(s):
- 1847811
- NSF-PAR ID:
- 10497157
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- Nano Letters
- Volume:
- 23
- Issue:
- 7
- ISSN:
- 1530-6984
- Page Range / eLocation ID:
- 2483 to 2489
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
null (Ed.)Quantum anomalous Hall effect has been observed in magnetically doped topological insulators. However, full quantization, up until now, is limited within the sub–1 K temperature regime, although the material’s magnetic ordering temperature can go beyond 100 K. Here, we study the temperature limiting factors of the effect in Cr-doped (BiSb) 2 Te 3 systems using both transport and magneto-optical methods. By deliberate control of the thin-film thickness and doping profile, we revealed that the low occurring temperature of quantum anomalous Hall effect in current material system is a combined result of weak ferromagnetism and trivial band involvement. Our findings may provide important insights into the search for high-temperature quantum anomalous Hall insulator and other topologically related phenomena.more » « less
-
Realization of ferromagnetic (FM) interlayer coupling in magnetic topological insulators (TIs) of the MnBi 2 Te 4 family of materials (MBTs) may pave the way for realizing the high-temperature quantum anomalous Hall effect (high- T QAHE). Here we propose a generic dual d-band (DDB) model to elucidate the energy difference (Δ E = E AFM − E FM ) between the AFM and FM coupling in transition-metal (TM)-doped MBTs, where the valence of TMs splits into d-t 2g and d-e g sub-bands. Remarkably, the DDB shows that Δ E is universally determined by the relative position of the dopant (X) and Mn d-e g / t 2g bands, . If Δ E d > 0, then Δ E > 0 and the desired FM coupling is favored. This surprisingly simple rule is confirmed by first-principles calculations of hole-type 3d and 4d TM dopants. Significantly, by applying the DDB model, we predict the high- T QAHE in the V-doped Mn 2 Bi 2 Te 5 , where the Curie temperature is enhanced by doubling of the MnTe layer, while the topological order mitigated by doping can be restored by strain.more » « less
-
Abstract Integration of a quantum anomalous Hall insulator with a magnetically ordered material provides an additional degree of freedom through which the resulting exotic quantum states can be controlled. Here, an experimental observation is reported of the quantum anomalous Hall effect in a magnetically‐doped topological insulator grown on the antiferromagnetic insulator Cr2O3. The exchange coupling between the two materials is investigated using field‐cooling‐dependent magnetometry and polarized neutron reflectometry. Both techniques reveal strong interfacial interaction between the antiferromagnetic order of the Cr2O3and the magnetic topological insulator, manifested as an exchange bias when the sample is field‐cooled under an out‐of‐plane magnetic field, and an exchange spring‐like magnetic depth profile when the system is magnetized within the film plane. These results identify antiferromagnetic insulators as suitable candidates for the manipulation of magnetic and topological order in topological insulator films.
-
Abstract Van der Waals heterostructures offer great versatility to tailor unique interactions at the atomically flat interfaces between dissimilar layered materials and induce novel physical phenomena. By bringing monolayer 1 T’ WTe2, a two-dimensional quantum spin Hall insulator, and few-layer Cr2Ge2Te6, an insulating ferromagnet, into close proximity in an heterostructure, we introduce a ferromagnetic order in the former via the interfacial exchange interaction. The ferromagnetism in WTe2manifests in the anomalous Nernst effect, anomalous Hall effect as well as anisotropic magnetoresistance effect. Using local electrodes, we identify separate transport contributions from the metallic edge and insulating bulk. When driven by an AC current, the second harmonic voltage responses closely resemble the anomalous Nernst responses to AC temperature gradient generated by nonlocal heater, which appear as nonreciprocal signals with respect to the induced magnetization orientation. Our results from different electrodes reveal spin-polarized edge states in the magnetized quantum spin Hall insulator.
-
Abstract The quantum anomalous Hall (QAH) effect is characterized by a dissipationless chiral edge state with a quantized Hall resistance at zero magnetic field. Manipulating the QAH state is of great importance in both the understanding of topological quantum physics and the implementation of dissipationless electronics. Here, the QAH effect is realized in the magnetic topological insulator Cr‐doped (Bi,Sb)2Te3(CBST) grown on an uncompensated antiferromagnetic insulator Al‐doped Cr2O3. Through polarized neutron reflectometry (PNR), a strong exchange coupling is found between CBST and Al‐Cr2O3surface spins fixing interfacial magnetic moments perpendicular to the film plane. The interfacial coupling results in an exchange‐biased QAH effect. This study further demonstrates that the magnitude and sign of the exchange bias can be effectively controlled using a field training process to set the magnetization of the Al‐Cr2O3layer. It demonstrates the use of the exchange bias effect to effectively manipulate the QAH state, opening new possibilities in QAH‐based spintronics.