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Fabrication of a novel magnetic topological heterostructure and temperature evolution of its massive Dirac cone.

ABSTRACT: Materials that possess nontrivial topology and magnetism is known to exhibit exotic quantum phenomena such as the quantum anomalous Hall effect. Here, we fabricate a novel magnetic topological heterostructure Mn₄Bi₂Te₇/Bi₂Te₃ where multiple magnetic layers are inserted into the topmost quintuple layer of the original topological insulator Bi₂Te₃. A massive Dirac cone (DC) with a gap of 40-75?meV at 16?K is observed. By tracing the temperature evolution, this gap is shown to gradually decrease with increasing temperature and a blunt transition from a massive to a massless DC occurs around 200-250?K. Structural analysis shows that the samples also contain MnBi₂Te₄/Bi₂Te₃. Magnetic measurements show that there are two distinct Mn components in the system that corresponds to the two heterostructures; MnBi₂Te₄/Bi₂Te₃ is paramagnetic at 6?K while Mn₄Bi₂Te₇/Bi₂Te₃ is ferromagnetic with a negative hysteresis (critical temperature ~20?K). This novel heterostructure is potentially important for future device applications.

SUBMITTER: Hirahara T

PROVIDER: S-EPMC7515900 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Fabrication of a novel magnetic topological heterostructure and temperature evolution of its massive Dirac cone.

Hirahara T T Otrokov M M MM Sasaki T T TT Sumida K K Tomohiro Y Y Kusaka S S Okuyama Y Y Ichinokura S S Kobayashi M M Takeda Y Y Amemiya K K Shirasawa T T Ideta S S Miyamoto K K Tanaka K K Kuroda S S Okuda T T Hono K K Eremeev S V SV Chulkov E V EV

Nature communications 20200924 1

Materials that possess nontrivial topology and magnetism is known to exhibit exotic quantum phenomena such as the quantum anomalous Hall effect. Here, we fabricate a novel magnetic topological heterostructure Mn4Bi2Te7/Bi2Te3 where multiple magnetic layers are inserted into the topmost quintuple layer of the original topological insulator Bi2Te3. A massive Dirac cone (DC) with a gap of 40-75 meV at 16 K is observed. By ...[more]

PMID: 32973165

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Project description:A new kind of magnetically-doped antiferromagnetic (AFM) topological insulators (TIs) with stoichiometry Bi1.09Gd0.06Sb0.85Te3 has been studied by angle-resolved photoemission spectroscopy (ARPES), superconducting magnetometry (SQUID) and X-ray magnetic circular dichroism (XMCD) with analysis of its electronic structure and surface-derived magnetic properties at different temperatures. This TI is characterized by the location of the Dirac gap at the Fermi level (EF) and a bulk AFM coupling below the Neel temperature (4-8 K). At temperatures higher than the bulk AFM/PM transition, a surface magnetic layer is proposed to develop, where the coupling between the magnetic moments located at magnetic impurities (Gd) is mediated by the Topological Surface State (TSS) via surface Dirac-fermion-mediated magnetic coupling. This hypothesis is supported by a gap opening at the Dirac point (DP) indicated by the surface-sensitive ARPES, a weak hysteresis loop measured by SQUID at temperatures between 30 and 100 K, XMCD measurements demonstrating a surface magnetic moment at 70 K and a temperature dependence of the electrical resistance exhibiting a mid-gap semiconducting behavior up to temperatures of 100-130 K, which correlates with the temperature dependence of the surface magnetization and confirms the conclusion that only TSS are located at the EF. The increase of the TSS's spectral weight during resonant ARPES at a photon energy corresponding to the Gd 4d-4f edge support the hypothesis of a magnetic coupling between the Gd ions via the TSS and corresponding magnetic moment transfer at elevated temperatures. Finally, the observed out-of-plane and in-plane magnetization induced by synchrotron radiation (SR) due to non-equal depopulation of the TSS with opposite momentum, as seen through change in the Dirac gap value and the k∥-shift of the Dirac cone (DC) states, can be an indicator of the modification of the surface magnetic coupling mediated by the TSS.

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Fabrication of a novel magnetic topological heterostructure and temperature evolution of its massive Dirac cone.

Publications

Fabrication of a novel magnetic topological heterostructure and temperature evolution of its massive Dirac cone.

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