源于超导HgBa2CuO4 +δ中低能带Hg-O的Q=0集体模
Q=0 collective modes originating from the low-lying Hg-O band in the superconducting HgBa2CuO4+δ
摘要：
基于最近发现的两个Q \sim 0集体模[Y. Li等人，Nature 468，283（2010）; ibid Nat.Phys.8，404（2012）]中的单层HgBa 2CuO 4 +δ，其通常被认为是赝能隙的轨道电流起源的证据，我们检查了由第一原理计算约束的替代的和无折射的情况。我们发现，除了常见的CuO 2能带外，在费米能级附近还存在一个Hg-O杂化态，它对该体系的低能基态有贡献.我们计算的自旋激发谱的基础上的随机相位近似的超导态使用两个带模型，并表明，集体模式的多轨道通道中出现在Q=0。这种模式在能量上分裂，但仍保持在Q \sim 0，因为赝能隙的发展打破了自旋通道中的平移对称性和时间反转对称性，从而使电子态脱离。赝能隙态下的动力学模和静态矩的观测结果与实验结果符合得很好。这一建议的一个可验证的预测是磁秩序的发展也在Hg-O层。通过光学研究探测Hg-O带，或Hg-O层中的磁矩将是该计算的测试。
英文摘要：
Motivated by the recent discovery of two Q\sim0 collective modes [Y. Li et al., Nature 468, 283 (2010); ibid Nat. Phys. 8, 404 (2012)] in the single-layer HgBa2CuO4+δ, which are often taken as evidence of the orbital current origin of a pseudogap, we examine an alternative and assumption-free scenario constrained by first-principle calculations. We find that in addition to the common CuO2 band, a hybridized Hg-O state is present in the vicinity of the Fermi level, and that it contributes to the low-energy ground state of this system. We calculate the spin-excitation spectrum based on the random-phase-approximation in the superconducting state using a two band model and show that a collective mode in the multi-orbital channel arises at Q=0. This mode splits in energy, yet remains at Q\sim0 as the pseudogap develops breaking both translational and time-reversal symmetries in the spin-channel, and thus gap out the electrnic states. The observations of the dynamical mode and static moment in the pseudogap state are in good accord with experimental observations. A verifiable prediction of this proposal is the development of magnetic order also in the Hg-O layer. Detection of Hg-O band via optical study, or magnetic moment in the Hg-O layer will be tests of this calculation.
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