The electronic fluid in cuprate superconductors and NMR

Nuclear magnetic resonance (NMR) is a powerful technique to explore quantum fluids in solids. Recently it was found that a number of early conclusions derived with NMR about the cuprates were flawed, as is easily seen from an overview of all cuprate planar copper shifts [1] and relaxation data [2,3]. For example, there is no evidence for special electronic spin fluctuations [2,3], and, the uniform magnetic response above Tc shows hitherto unknown behaviour [1,2]. The latter implies a large spin shift below Tc for one direction of the external magnetic field, while the nuclear relaxation ceases completely for all cuprates [3]. This must have consequences for the pairing. To shed more light on this peculiar behaviour, we discuss data for other nuclei and their relation to the local charge symmetry, which sustains the existence of this unusual spin shift.

[1] J. Haase, M. Jurkutat, J. Kohlrautz, Condensed Matter 2, 16 (2017).
[2] M. Avramovska, D. Pavićević, and J. Haase, J Supercond 243, 337 (2019).
[3] M. Jurkutat, M. Avramovska, G. V. M. Williams, D. Dernbach, D. Pavićević, and J. Haase, J Supercond 155, 629 (2019).