电荷密度波化合物中的八重费米子激发
Eightfold Fermionic Excitation in a Charge Density Wave Compound
摘要：
凝聚态系统中的非常规准粒子激发已成为当前研究的重要前沿之一。除了二次和四次简并的外尔和狄拉克费米子，三次、六次和八次对称保护的简并已经被预测，但是在固态材料中实现仍然具有挑战性。在这里，电荷密度波化合物TaTe 4被提出来保持八重费米子激发和狄拉克点的能带。制备了高质量的TaTe 4单晶，其中电荷密度波通过直接成像表面上的原子结构和约45 meV的赝能隙来揭示。TaTe 4的Shubnikov de-Haas振荡与能带结构计算结果一致。扫描隧道显微镜揭示了TaTe 4表面的原子台阶边缘态。这一工作揭示了电荷密度波能够诱导新的拓扑相，为凝聚态材料中的新激发提供了新的思路。
英文摘要：
Unconventional quasiparticle excitations in condensed matter systems have become one of the most important research frontiers. Beyond two- and fourfold degenerate Weyl and Dirac fermions, three-, six- and eightfold symmetry protected degeneracies have been predicted however remain challenging to realize in solid state materials. Here, charge density wave compound TaTe4 is proposed to hold eightfold fermionic excitation and Dirac point in energy bands. High quality TaTe4 single crystals are prepared, where the charge density wave is revealed by directly imaging the atomic structure and a pseudogap of about 45 meV on the surface. Shubnikov de-Haas oscillations of TaTe4 are consistent with band structure calculation. Scanning tunneling microscopy reveals atomic step edge states on the surface of TaTe4. This work uncovers that charge density wave is able to induce new topological phases and sheds new light on the novel excitations in condensed matter materials.
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