Abstract Spin-gapless semiconductors are recently discovered class of materials that behave as an insulator for one spin channel and as a zero-gap semiconductor for the opposite spin. Here, we show from first-principle calculations that one such material Ti2CoSi predicted to exhibit spin-gapless semiconductivity has an energetically close non-spin-polarized phase. In particular, we show that the regular Heusler phase of this material is non-magnetic, while the inverted Heusler phase is nearly spin-gapless semiconducting, with a very small energy difference of ≈ 0.1 eV per 16-atom cell, in favor of the regular Heusler structure. Moreover, we also show that a 100% spin polarization in inverted Heusler phase is detrimentally affected by the emergence of surface states in thin-film geometry. These results need to be taken into account for realistic implementations of this and similar materials in nano-device applications, which rely on highly spin-polarized current in thin-film geometry.

中文翻译：

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在 Ti2CoSi 中实现自旋无间隙半导体的各种挑战

摘要 无自旋无隙半导体是最近发现的一类材料，其表现为一个自旋通道的绝缘体和相反自旋的零隙半导体。在这里，我们从第一性原理计算表明，一种预测显示自旋无隙半导体的此类材料 Ti2CoSi 具有能量上接近的非自旋极化相。特别是，我们表明这种材料的规则 Heusler 相是非磁性的，而倒置的​​ Heusler 相几乎是自旋无隙的半导体，每个 16 原子电池的能量差约为 0.1 eV，有利于常规 Heusler 结构。此外，我们还表明，倒赫斯勒相中的 100% 自旋极化受到薄膜几何结构中表面态出现的不利影响。