Van Hove exciton model of the cuprate pseudogap

There is a dichotomy of the Van Hove singularity (VHS) in cuprates, with competing instabilities at wave numbers q = (0,0) (diverging density-of-states [DOS]) and Q=(pi,pi). The latter dominates for small doping x and/or small second-neighbor hopping t', but in most cuprates the DOS anomaly and associated anti-nodal nesting dominate at higher x. The Q-VHS displays an intimate connection with pseudogap physics [1]. The strong sensitivity of the Q-VHS to Pauli blocking indicates a close connection with excitonic physics, suggesting that the Mott-Slater transition that we find is related to the BEC-BCS transition of an underlying excitonic insulator [2].


1 R.S. Markiewicz, I.G. Buda, P. Mistark, C. Lane, and A. Bansil, Scientific Reports 7, 44008 (2017).

2. R.S. Markiewicz and A. Bansil, arXiv:1708.2270