Investigation of anomalous ground state on geometrically frustrated magnet

焦绿石氧化物Tb_2Ti_2O_7在20mK以下没有表现出任何长程有序，真正的基态尚未建立。最近，理论界提出，在这种材料的基态中实现了量子自旋冰态。这一态由六个经典自旋冰态通过第一激发双态的杂化叠加而成。从直流磁化强度和比热测量到100mK的磁场沿[100]，[110]，[111]方向，我们澄清了类伊辛磁各向异性，并在0.5K以下观察到类似于自旋冰化合物的Kagome平台的平台特征。此外，我们还观察到了比热的反常现象，表明了向量子自旋冰态的相变。

Pyrochlore oxide Tb_2Ti_2O_7 dose not show any long range ordering down to 20mK and the true ground state had not established yet. Recently, theorists proposed that in the ground state of this material the "quantum spin ice" state is realized. This state consists of the superposition of six classical spin ice states by the hybridization of first excited doublet. From the DC magnetization and specific heat measurements down to 100 mK in the magnetic field along [100], [110], [111] directions, we clarified the Ising-like magnetic anisotropy and the plateau-like feature is observed below 0.5K similar to the Kagome-plateau of spin ice compounds. In addition, we observed the anomaly in specific heat indicating the phase transition to quantum spin ice state.