AI 中文总结
本研究通过第一性原理计算，揭示了交替磁体CsCr$_2$S$_2$O中，已存在的C型反铁磁序与电子关联协同，通过轨道选择性机制，驱动键序与次级自旋密度波耦合，实现金属-绝缘体转变的新机制。
AI 中文摘要
在CsCr$_2$S$_2$O中，识别出由键序（BO）与次级自旋密度波（SDW）耦合驱动的金属-绝缘体转变（MIT）。这种耦合的产生源于已存在的C型反铁磁（C-AFM）序破坏了时间反演对称性。第一性原理计算揭示了轨道选择性物理：Cr-$d_{yz}$轨道形成局域磁矩并建立交替磁序，而Cr-$d_{xz}$轨道保持金属性并与S-$p_z$轨道杂化，因此低能物理由Cr-$d_{xz}$和S-$p_z$轨道主导。 onsite相互作用随后增强了巡游$d_{xz}$电子的次级SDW（sSDW）不稳定性，该不稳定性与Cr-$d_{xz}$-S-$p_z$键序耦合。由此产生的耦合sSDW-BO同时产生了实验观测到的结构畸变、电荷歧化、局域Cr磁矩调制和能隙打开。本研究结果确立了一种轨道选择性机制，其中已存在的交替磁性与电子关联协同驱动结构型MIT。
英文摘要
A metal-insulator transition (MIT) driven by bond order (BO) coupled with a secondary spin-density wave (SDW) is identified in CsCr$_2$S$_2$O. Such coupling is enabled as a result of the broken time-reversal symmetry due to the pre-existing C-type antiferromagnetic (C-AFM) order. First-principles calculations reveal an orbital-selective physics that Cr-$d_{yz}$ orbitals form local moments and establish the altermagnetic order, while the Cr-$d_{xz}$ orbitals remain metallic and hybridize with S-$p_z$. Thus the low-energy physics is governed by the Cr-$d_{xz}$ and S-$p_z$ orbitals. On-site interactions then enhance a secondary SDW ($s$SDW) instability of the itinerant $d_{xz}$ electrons, which couples to the Cr-$d_{xz}$-S-$p_z$ bonding order. The resulting coupled $s$SDW-BO simultaneously produces experimentally observed structural distortion, charge disproportionation, local Cr-moment modulation, and gap opening. Our results establish an orbital-selective mechanism upon which pre-existing altermagnetism and electronic correlations cooperate to drive a structural MIT.
