Thermal Hall conductivity in the cuprate Mott insulators Nd2CuO4 and Sr2CuO2Cl2

The heat carriers responsible for the unexpectedly large thermal Hall conductivity of the cuprate Mott insulator La2CuO4 were recently shown to be phonons. However, the mechanism by which phonons in cuprates acquire chirality in a magnetic field is still unknown. Here, we report a similar thermal Hall conductivity in two cuprate Mott insulators with significantly different crystal structures and magnetic orders – Nd2CuO4 and Sr2CuO2Cl2 – and show that two potential mechanisms can be excluded – the scattering of phonons by rare-earth impurities and by structural domains. Our comparative study further reveals that orthorhombicity, apical oxygens, the tilting of oxygen octahedra and the canting of spins out of the CuO2 planes are not essential to the mechanism of chirality. Our findings point to a chiral mechanism coming from a coupling of acoustic phonons to the intrinsic excitations of the CuO2 planes.

Температурный сдвиг бесфононных f-f-линий люминесценции Er-=SUP=-3+-=/SUP=- в квантовом параэлектрике KTaO-=SUB=-3-=/SUB=-

In KTaO_3:Er crystals, we observed a temperature shift, unusual for rare earth impurities, for narrow zero-phonon luminescence lines, due to the ^4 S _3/2 → ^4 I _13/2, ^4 F _9/2 → ^4 I _15/2, and ^4 S _3/2 → ^4 I _15/2 transitions in Er^3+ impurity ions. The magnitude of the shifts turned out to be comparable with the large shifts of the R lines of the Cr^3+ luminescence in SrTiO_3:Cr and KTaO_3:Cr crystals, that is, substantially larger than that for the three-charged rare earth ions usually observed in the f – f luminescence spectra in ionic crystals.

Tracing origins of uranium ore concentrates (UOCs) by multidimensional statistical analysis of rare-earth impurities

A novel approach using REE data of uranium ores instead of UOC samples to trace the origins of unknown UOCs was developed.