论文标题
磁场诱导的范德华磁体中的量子相变
Magnetic field-induced quantum phase transitions in a van der Waals magnet
论文作者
论文摘要
探索新的参数制度以实现和控制物质的新阶段一直是现代冷凝物质物理研究的主要主题。最近在几乎独立的单层原子晶体中发现了2D磁性的发现已经导致观察到散装对应物中缺少许多新型磁性现象。磁性和晶体结构之间的这种复杂的相互作用为探索这个新的2D参数制度中的量子相变提供了足够的机会。在这里，使用磁场和依赖温度的圆形拉曼光谱，我们绘制了CRI3的相图，该相位图已知是其2D膜中的层次AFM，在其3D体积中是FM。但是，我们在3D CRI3散装晶体中揭示了一种新型的层状AFM和FM的混合状态，其中分层的AFM在表面层中存活，FM出现在更深的散装层中。然后，我们表明表面层次在2 t的临界磁场下转移到FM中，类似于在少数层情况下发现的磁场。有趣的是，与这种磁相变的同时，我们发现了一个一阶结构相变，它改变了从C3I到C2H的晶体学点基团，因此从对称的角度来看，这个单斜结构相属于3D Nematic Order Order rorder corvisical class。 Our result not only unveils the complex single magnon behavior in 3D CrI3, but also settles down the puzzle of how CrI3 transits from a bulk FM to a thin layered AFM semiconductor, despite recent efforts in understanding the origin of layered AFM in CrI3 thin layer, and reveals the intimate relationship between the layered AFM-to-FM and the crystalline rhombohedral-to-monoclinic phase transitions.这些发现进一步为将来的基于2D磁铁的机械设备打开了机会。
Exploring new parameter regimes to realize and control novel phases of matter has been a main theme in modern condensed matter physics research. The recent discovery of 2D magnetism in nearly freestanding monolayer atomic crystals has already led to observations of a number of novel magnetic phenomena absent in bulk counterparts. Such intricate interplays between magnetism and crystalline structures provide ample opportunities for exploring quantum phase transitions in this new 2D parameter regime. Here, using magnetic field and temperature dependent circularly polarized Raman spectroscopy of phonons and magnons, we map out the phase diagram of CrI3 that has been known to be a layered AFM in its 2D films and a FM in its 3D bulk. We, however, reveal a novel mixed state of layered AFM and FM in 3D CrI3 bulk crystals where the layered AFM survives in the surface layers and the FM appears in deeper bulk layers. We then show that the surface layered AFM transits into the FM at a critical magnetic field of 2 T, similar to what was found in the few layer case. Interestingly, concurrent with this magnetic phase transition, we discover a first-order structural phase transition that alters the crystallographic point group from C3i to C2h and thus, from a symmetry perspective, this monoclinic structural phase belongs to the 3D nematic order universality class. Our result not only unveils the complex single magnon behavior in 3D CrI3, but also settles down the puzzle of how CrI3 transits from a bulk FM to a thin layered AFM semiconductor, despite recent efforts in understanding the origin of layered AFM in CrI3 thin layer, and reveals the intimate relationship between the layered AFM-to-FM and the crystalline rhombohedral-to-monoclinic phase transitions. These findings further open up opportunities for future 2D magnet-based magneto-mechanical devices.
