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Large magnetic gap at the Dirac point in Bi_2Te_3/MnBi_2Te_4 heterostructures

机译：Bi_2Te_3 / MnBi_2Te_4异质结构中Dirac点处的大磁隙

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Magnetically doped topological insulators enable the quantum anomalous Hall effect (QAHE), which provides quantized edge states for lossless charge-transport applications(1-8). The edge states are hosted by a magnetic energy gap at the Dirac point(2), but hitherto all attempts to observe this gap directly have been unsuccessful. Observing the gap is considered to be essential to overcoming the limitations of the QAHE, which so far occurs only at temperatures that are one to two orders of magnitude below the ferromagnetic Curie temperature, T-C (ref. (8)). Here we use low-temperature photoelectron spectroscopy to unambiguously reveal the magnetic gap of Mn-doped Bi2Te3, which displays ferromagnetic out-of-plane spin texture and opens up only below T-C. Surprisingly, our analysis reveals large gap sizes at 1 kelvin of up to 90 millielectronvolts, which is five times larger than theoretically predicted(9). Using multiscale analysis we show that this enhancement is due to a remarkable structure modification induced by Mn doping: instead of a disordered impurity system, a self-organized alternating sequence of MnBi2Te4 septuple and Bi2Te3 quintuple layers is formed. This enhances the wavefunction overlap and size of the magnetic gap(10). Mn-doped Bi2Se3 (ref. (11)) and Mn-doped Sb2Te3 form similar heterostructures, but for Bi2Se3 only a nonmagnetic gap is formed and the magnetization is in the surface plane. This is explained by the smaller spin-orbit interaction by comparison with Mn-doped Bi2Te3. Our findings provide insights that will be crucial in pushing lossless transport in topological insulators towards room-temperature applications.
机译：磁性掺杂的拓扑绝缘体可实现量子异常霍尔效应（QAHE），该效应为无损电荷传输应用（1-8）提供了量化的边缘状态。边缘状态由狄拉克点（2）上的磁能隙所主导，但迄今为止，直接观察该隙的所有尝试均未成功。观察间隙对克服QAHE的局限性至关重要，QAHE局限性迄今仅在比铁磁居里温度T-C低一到两个数量级的温度下才会发生（参考文献（8））。在这里，我们使用低温光电子能谱法清楚地揭示了Mn掺杂的Bi2Te3的磁隙，该磁隙显示出铁磁面外自旋织构，并且仅在T-C以下打开。出人意料的是，我们的分析显示出在1开尔文处的最大间隙尺寸高达90毫伏，是理论上预测的五倍（9）。使用多尺度分析，我们表明这种增强是由于Mn掺杂引起的显着结构修饰：代替无序杂质系统，形成了自组织的MnBi2Te4六元组和Bi2Te3五元组的交替序列。这增强了波函数的重叠和磁隙（10）的大小。 Mn掺杂的Bi2Se3（参考文献（11））和Mn掺杂的Sb2Te3形成相似的异质结构，但对于Bi2Se3，仅形成非磁性间隙，并且磁化作用在表面上。与Mn掺杂的Bi2Te3相比，自旋轨道相互作用较小，可以解释这一点。我们的发现提供了一些见解，这些见解对于将拓扑绝缘子的无损传输推向室温应用至关重要。

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  • 来源
    《Nature》 |2019年第7787期|423-428|共6页
  • 作者

    Rienks E. D. L.; Wimmer S.; Sanchez-Barriga J.; Caha O.; Mandal P. S.; Ruzicka J.; Ney A.; Steiner H.; Volobuev V. V.; Groiss H.; Albu M.; Kothleitner G.; Michalicka J.; Khan S. A.; Minar J.; Ebert H.; Bauer G.; Freyse F.; Varykhalov A.; Rader O.; Springholz G.;

  • 作者单位

    Helmholtz Zentrum Berlin Mat & Energie Elektronenspeicherring BESSY 2 Berlin Germany|Tech Univ Dresden Inst Festkorperphys Dresden Germany|Leibniz Inst Festkorper & Werkstoffforsch Dresden Dresden Germany;

    Johannes Kepler Univ Linz Inst Halbleiter & Festkorperphys Linz Austria;

    Helmholtz Zentrum Berlin Mat & Energie Elektronenspeicherring BESSY 2 Berlin Germany;

    Masaryk Univ Dept Condensed Matter Phys Brno Czech Republic;

    Helmholtz Zentrum Berlin Mat & Energie Elektronenspeicherring BESSY 2 Berlin Germany|Univ Potsdam Inst Phys & Astron Potsdam Germany;

    Johannes Kepler Univ Linz Inst Halbleiter & Festkorperphys Linz Austria|Natl Tech Univ Kharkiv Polytech Inst Kharkov Ukraine|Polish Acad Sci Int Res Ctr MagTop Warsaw Poland|Polish Acad Sci Inst Phys Warsaw Poland;

    Johannes Kepler Univ Linz Christian Doppler Lab Nanoscale Phase Transformat Zentrum Oberflachen & Nanoanalyt Linz Austria;

    Graz Univ Technol Graz Ctr Electron Microscopy Inst Electron Microscopy & Nanoanal Graz Austria;

    Brno Univ Technol Cent European Inst Technol Brno Czech Republic;

    Univ West Bohemia New Technol Res Ctr Plzen Czech Republic;

    Ludwig Maximilians Univ Munchen Dept Chem Munich Germany;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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