氟氧化物BaBiO $_2$ F中费米能级的移动和拓扑绝缘相的实现
Shifting of Fermi Level and Realization of Topological Insulating Phase in the Oxyfluoride BaBiO$_2$F
摘要：
BaBiO $_3$虽然具有对称性保护的狄拉克态，但不是拓扑绝缘体的缺点通过经由π移动费米能级（E $_F$）来克服。密度泛函理论计算表明，电子的引入既不影响自旋轨道耦合，也不影响态的宇称，但它作为一个理想的电子给体移动E $_F$。我们发现，33%的掺杂足以使E $_F$移动$\sim$ 2 eV，使不变的狄拉克态位于其上，使BaBiO $_2$ F成为拓扑绝缘体。氟化立方化合物可以通过实验合成，因为声子研究预测了$\sim$ 500 K以上的动力学稳定性。此外，狄拉克态被发现是对低温相晶格畸变，使结构单斜不变。这些结果具有实际意义，因为它们开辟了通过适当的掺杂将超导氧化物族ABiO $_3$（A = Na，K，Cs，Ba，Sr，Ca）转化为真正的拓扑绝缘体的可能性。
英文摘要：
The disadvantage of BaBiO$_3$ of not being a topological insulator despite having symmetry protected Dirac state is overcome by shifting the Fermi level (E$_F$) via fluorination. The DFT calculations reveal that the fluorination neither affects the spin-orbit coupling nor the parity of the states, but it acts as a perfect electron donor to shift the E$_F$. We find that 33 % fluorination is sufficient to shift the E$_F$ by $\sim$ 2 eV so that the invariant Dirac state lies on it to make BaBiO$_2$F a topological insulator. The fluorinated cubic compound can be experimentally synthesized as the phonon studies predict dynamical stability above $\sim$ 500 K. Furthermore, the Dirac states are found to be invariant against the low-temperature phase lattice distortion which makes the structure monoclinic. The results carry practical significance as they open up the possibility of converting the family of superconducting oxides, ABiO$_3$ (A = Na, K, Cs, Ba, Sr, Ca), to real topological insulator through appropriate fluorination.
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