Electronic Raman scattering in the 2D antiferromagnet NiPS 3

Electronic Raman scattering activates the investigation of d-d excitations and electron-spin coupling in 2D antiferromagnets.

Fermi surface instabilities in electronic Raman scattering of the metallic kagome lattice CsV3Sb5

Understanding the link between a charge density wave (CDW) instability and superconductivity is a central theme of the 2D metallic kagome compounds AV3Sb5 (A=K, Rb, and Cs). Using polarization-resolved electronic Raman spectroscopy, we shed light on Fermi surface fluctuations and electronic instabilities. We observe a quasielastic peak (QEP) whose spectral weight is progressively enhanced towards the superconducting transition. The QEP temperature-dependence reveals a steep increase in coherent in-plane charge correlations within the charge-density phase. In contrast, out-of-plane charge fluctuations remain strongly incoherent across the investigated temperature range. In-plane phonon anomalies appear at T* ≈ 50 K in addition to right below TCDW ≈ 95 K, while showing no apparent evidence of reduced symmetry at low temperatures. In conjunction with the consecutive phonon anomalies within the CDW state, our electronic Raman data unveil additional electronic instabilities that persist down to the superconducting phase, thereby offering a superconducting mechanism.

Fallacies on pairing symmetry and intrinsic electronic Raman spectrum in high-Tc cuprate superconductors

Certain significant fallacies are involved in discussions of the high-[Formula: see text] mechanism unsolved for over 30 years in cuprate superconductors. These fallacies are explored with the aim of unraveling this mechanism. Moreover, using polarized electronic Raman scattering in inhomogeneous underdoped cuprate superconductors, the intrinsic nonlinear Raman spectrum is obtained by subtracting the pseudogap characteristic of a nonlinear from the linear Raman spectrum measured in the [Formula: see text] mode of the node area below the critical temperature. The intrinsic nonlinear behavior implies the existence of the nodal superconducting gap denying [Formula: see text]-wave pairing symmetry. An origin of the nodal superconducting gap is discussed.