Charge density wave energy scale in superconducting cuprates

An outstanding challenge in high-T_c cuprates is to understand how charge density wave order is related to the pseudogap and superconducting phases [1]. To address this issue it is important to extract the energy scale Δ_CDW associated with the charge modulations, and to compare it with the pseudogap (PG) Δ_PG and the superconducting gap Δ_SC. However, while T_CDW is well-characterized from earlier works [2] little has been known about Δ_CDW until now. We will report the extraction of Δ_CDW for several cuprates using electronic Raman spectroscopy [3]. We observe that Δ_CDW increases in a manner similar to the doping dependence of Δ_PG and Δ_SC. This reveals that the three phases have a common microscopic origin. In addition, we find that Δ_CDW ≈ Δ_SC over a substantial doping range, which suggests that CDW and superconducting phases are intimately related, for example intertwined or connected by an emergent symmetry [1, 4-6].

[1] E.Fradkin et al., Rev. Mod. Phys. 87, 457 (2015).
[2] R.Comin etl al., Annu. Rev. Condens. Matter Phys. 7, 369 (2016).
[3] B.Loret et al., arXiv:1808.08198 (2018).
[4] K.B.Efetov et al., Nat. Phys. 194 9, 442 (2013).
[5] S.Sachdev et al., Phys. Rev. Lett. 111, 027202 (2013).
[6] Y.Wang et al., Phys. Rev. Lett. 114, 197001 (2015).