Emergence of Orbital Nematicity in the Tetragonal Phase of BaFe2(As1−xPx)2
Emergence of Orbital Nematicity in the Tetragonal Phase of BaFe2(As1−xPx)2
复制标题
DOI：
10.7566/jpsj.84.043705
复制
发表时间：
2015-03
影响因子：
1.7
通讯作者：
T. Iye;M. Julien;H. Mayaffre;M. Horvati'c;C. Berthier;K. Ishida;H. Ikeda;S. Kasahara;T. Shibauchi
中科院分区：
文献类型：
--
作者：
T. Iye;M. Julien;H. Mayaffre;M. Horvati'c;C. Berthier;K. Ishida;H. Ikeda;S. Kasahara;T. Shibauchi
本文报道了BaFe_2（As_（0.96）P_（0.04））_2单晶在结构转变温度TS_（\simeq \）121 K以上，平行于[110]o和[100]o方向磁场下的~（75）As-NMR测量结果.两个场方向之间的线宽的大的差异揭示了电场梯度的面内各向异性，即使在四相。这提供了As-4px和4py轨道之间人口不平衡的微观证据，|nx − ny|/|NX + NY|在T → TS时，Fe-3dxz和dyz电子轨道有序化的自然结果。令人惊讶的是，发现这种轨道极化在室温附近已经是静态的，这表明它是由无序对各向异性轨道涨落的钉扎引起的。该效应被发现是更强的低于160 K，这与在以前的扭矩和光电发射测量的向列性的外观相一致。这些结果施加了很强的约束微观模型的非线性状态。
We report on 75As-NMR measurements in single crystalline BaFe2(As0.96P0.04)2 for magnetic fields parallel to the orthorhombic [110]o and [100]o directions above the structural transition temperature TS \( \simeq \) 121 K. A large difference in the linewidth between the two field directions reveals in-plane anisotropy of the electric field gradient, even in the tetragonal phase. This provides microscopic evidence of population imbalance between As-4px and 4py orbitals, which reaches |nx − ny|/|nx + ny| ∼ 15% at T → TS and is a natural consequence of the orbital ordering of Fe-3dxz and dyz electrons. Surprisingly, this orbital polarization is found to be already static near room temperature, suggesting that it arises from the pinning of anisotropic orbital fluctuations by disorder. The effect is found to be stronger below ∼160 K, which coincides with the appearance of nematicity in previous torque and photoemission measurements. These results impose strong constraints on microscopic models of the nematic state.