Nasu Joji, Kato Yasuyuki, Yoshitake Junki, Kamiya Yoshitomo, Motome Yukitoshi
Department of Physics, Tokyo Institute of Technology, Meguro, Tokyo 152-8551, Japan.
Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan.
Phys Rev Lett. 2017 Mar 31;118(13):137203. doi: 10.1103/PhysRevLett.118.137203.
While phase transitions between magnetic analogs of the three states of matter-a long-range ordered state, paramagnet, and spin liquid-are extensively studied, the possibility of "liquid-liquid" transitions, namely, between different spin liquids, remains elusive. By introducing the additional Ising coupling into the honeycomb Kitaev model with bond asymmetry, we discover that the Kitaev spin liquid turns into a spin-nematic quantum paramagnet before a magnetic order is established by the Ising coupling. The quantum phase transition between the two liquid states accompanies a topological change driven by fractionalized excitations, the Z_{2} gauge fluxes, and is of first order. At finite temperatures, this yields a persisting first-order transition line that terminates at a critical point located deep inside the regime where quantum spins are fractionalized. It is suggested that similar transitions may occur in other perturbed Kitaev magnets with bond asymmetry.
虽然对物质三态的磁性类似物之间的相变——长程有序态、顺磁体和自旋液体——进行了广泛研究，但“液-液”转变，即在不同自旋液体之间转变的可能性仍然难以捉摸。通过将额外的伊辛耦合引入具有键不对称性的蜂窝状基泰耶夫模型，我们发现基泰耶夫自旋液体在伊辛耦合建立磁序之前转变为自旋向列量子顺磁体。这两种液态之间的量子相变伴随着由分数化激发、Z₂规范通量驱动的拓扑变化，且是一级相变。在有限温度下，这产生了一条持续的一级相变线，该线在量子自旋分数化区域深处的临界点处终止。有人提出，在其他具有键不对称性的受扰基泰耶夫磁体中可能会发生类似的转变。
