Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada.
Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada and Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada and Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany.
Phys Rev Lett. 2014 Mar 28;112(12):127002. doi: 10.1103/PhysRevLett.112.127002. Epub 2014 Mar 26.
Spin-orbit coupling has been conjectured to play a key role in the low-energy electronic structure of Sr2RuO4. By using circularly polarized light combined with spin- and angle-resolved photoemission spectroscopy, we directly measure the value of the effective spin-orbit coupling to be 130±30 meV. This is even larger than theoretically predicted and comparable to the energy splitting of the dxy and dxz,yz orbitals around the Fermi surface, resulting in a strongly momentum-dependent entanglement of spin and orbital character in the electronic wavefunction. As demonstrated by the spin expectation value ⟨sk⃗·s-k⃗⟩ calculated for a pair of electrons with zero total momentum, the classification of the Cooper pairs in terms of pure singlets or triplets fundamentally breaks down, necessitating a description of the unconventional superconducting state of Sr2RuO4 in terms of these newly found spin-orbital entangled eigenstates.
自旋轨道耦合被推测在 Sr2RuO4 的低能电子结构中起着关键作用。通过使用圆偏振光结合自旋和角度分辨光发射光谱学，我们直接测量到有效自旋轨道耦合的值为 130±30 meV。这甚至比理论预测的还要大，与费米面附近 dxy 和 dxz,yz 轨道的能量分裂相当，导致电子波函数中自旋和轨道特性的强烈动量相关性纠缠。正如通过对总动量为零的一对电子的自旋期望值 ⟨sk⃗·s-k⃗⟩ 的计算所证明的那样，根据纯单态或三重态对库珀对进行分类从根本上瓦解，这需要根据这些新发现的自旋轨道纠缠本征态来描述 Sr2RuO4 的非常规超导态。
