Abstract

The electronic structure of magnetically doped topological insulator Bi_1.09Gd_0.06Sb_0.85Te₃ is studied in the vicinity of the Dirac point at various temperatures (above and below the Néel temperature, 1–35 K) and synchrotron radiation polarizations using angle-resolved photoelectron spectroscopy. It is shown that the energy gap exists in photoemission spectra at the Dirac point, which remains open above the long-range magnetic ordering temperature T_N. Measurements of magnetic properties by the superconducting magnetometry method show antiferromagnetic ordering with the paramagnetic transition temperature of 8.3 K. The studies of the temperature dependence of the Dirac cone state intensity by photoelectron spectroscopy confirm the existence of the magnetic transition and show the possibility of its indication directly from photoemission spectra. A more detailed analysis of the splitting between states of upper and lower Dirac cones (i.e., the energy gap) at the Dirac point in the photoelectron spectra shows the dependence of the gap at the Dirac point on the synchrotron radiation polarization type (28–30 meV for p-polarization and 22–25 meV for circularly polarized radiation of opposite chirality). The gap opening mechanism at the Dirac point above T_N due to “coupling” of Dirac fermions with opposite momenta and spin orientations due to their interaction with the spin texture formed immediately during photoemission in the region of the photoemission hole at the magnetic impurity atom (Gd). It is shown that the gap at the Dirac point, measured above T_N, is dynamic and is formed immediately during photoemission. In this case, the gap nature remains magnetic (even in the absence of long-range magnetic ordering) and is caused by properties of magnetic topological insulator, which does control the gap invariability when passing through T_N. The dynamic nature of the generated gap is confirmed by its dependence on synchrotron radiation polarization.

中文翻译：

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掺G拓扑绝缘子电子光谱中狄拉克点的空位打开机制

摘要

使用角分辨光电子在不同温度（高于和低于Néel温度，1-35 K）和狄拉克点附近研究了磁掺杂拓扑绝缘子Bi _1.09 Gd _0.06 Sb _0.85 Te ₃的电子结构。光谱学。结果表明，在狄拉克点处的光发射谱中存在能隙，该能隙在远距离磁有序温度T _N以上保持开放。用超导磁力法测量的磁性能显示顺磁转变温度为8.3 K时反铁磁有序。通过光电子能谱对狄拉克锥态强度的温度依赖性的研究证实了磁转变的存在并表明了其指示的可能性。直接来自光发射光谱。在光电子光谱的狄拉克点上上下狄拉克锥的状态之间的分裂（即能隙）的更详细分析显示，狄拉克点处的间隙与同步加速器辐射极化类型有关（28–30）兆电子伏为p极化波和22-25兆电子伏为相反手性的圆偏振辐射）。上方狄拉克点的缝隙打开机制T _N是由于狄拉克费米子与具有相反动量和自旋取向的“耦合”所致，这是由于它们与在光发射期间在磁性杂质原子（Gd）的光发射孔区域中立即形成的自旋织构相互作用。结果表明，在狄拉克点处的间隙在T _N之上测量是动态的，并且在光发射期间立即形成。在这种情况下，间隙性质保持磁性（即使在没有长距离磁序的情况下也是如此），并且是由磁性拓扑绝缘子的特性引起的，该特性确实控制了穿过T _N时的间隙不变性。所产生的间隙的动态性质由其对同步加速器辐射极化的依赖性来证实。