AI 中文总结
本文通过调节各向异性次近邻跃迁，在单轨道蜂窝晶格紧束缚模型中实现了狭义III型狄拉克锥，其临界点两侧存在I、II型狄拉克锥，且该模型还存在与狄拉克点能量重合的额外平线，可用于探索非常规热力学特性。
AI 中文摘要
临界倾斜狄拉克锥因二维无质量狄拉克费米子系统中具有的非常规电子特性而受到大量关注，其中狭义III型狄拉克锥的特征是沿连接两个狄拉克点的方向存在平坦色散。我们采用单轨道蜂窝晶格上的紧束缚模型，证明通过调节各向异性次近邻跃迁可以实现狭义III型狄拉克锥；在临界点两侧会出现I型和II型狄拉克锥，从而可系统研究跨越I型、狭义III型和II型区域的电子特性。我们进一步发现，该模型在动量空间中存在额外平线，其能量与狭义III型临界点处的狄拉克点能量重合。这种能带结构会显著增强费米能量处的态密度，因此与理想狭义III型狄拉克锥的预期相比，电子比热大幅提升。我们的结果表明，具有各向异性次近邻跃迁的蜂窝晶格为探索由狭义III型狄拉克锥与费米能量处额外平线的能量重合所产生的非常规热力学特性提供了一个简单平台。
英文摘要
Critically tilted Dirac cones have attracted considerable attention because of their unconventional electronic properties in two-dimensional massless Dirac-fermion systems. Among them, the narrow-sense type-III Dirac cone is characterized by a flat dispersion along the direction connecting the two Dirac points. Using a tight-binding model on a single-orbital honeycomb lattice, we demonstrate that narrow-sense type-III Dirac cones can be realized by tuning anisotropic next-nearest-neighbor hoppings. Type-I and type-II Dirac cones emerge on either side of the critical point, enabling a systematic investigation of the electronic properties across the type-I, narrow-sense type-III, and type-II regimes. We further find that the present model exhibits additional flat lines in momentum space whose energy coincides with the Dirac-point energy at the narrow-sense type-III critical point. This band structure produces a pronounced enhancement of the density of states at the Fermi energy and, consequently, a substantial enhancement of the electronic specific heat compared with that expected for an ideal narrow-sense type-III Dirac cone. Our results show that the honeycomb lattice with anisotropic next-nearest-neighbor hoppings provides a simple platform for exploring unconventional thermodynamic properties arising from the energy coincidence of narrow-sense type-III Dirac cones and additional flat lines at the Fermi energy.
Comments12 pages, 23 figures, The Supplemental Material is included as an Appendix
