Superconductivity in Ce-based cage compounds.

Cerium-based ternary compounds CeNiCdand CePdCddo not exhibit long-range order down to millikelvin temperature range. Given the large separation between Ce ions which significantly reduces the super-exchange interactions and vanishingly small Ruderman-Kittel-Kasuya-Yosida interaction, here we show that nodal superconductivity mediated by the valence fluctuations must be a ground state in these materials. We propose that the critical temperature for the superconducting transition can be significantly increased by applying hydrostatic pressure.

Interacting fermions in narrow-gap semiconductors with band inversion.

Highly unconventional behavior of the thermodynamic response functions has been experimentally observed in a narrow gap semiconductor samarium hexaboride. Motivated by these observations, we use renormalization group technique to investigate many-body instabilities in the-orbital narrow gap semiconductors with band inversion in the limit of weak coupling. By projecting out the double occupancy of the-states we formulate a low-energy theory describing the interacting particles in two hybridized electron- and hole-like bands.

Strong second harmonic generation in two-dimensional ferroelectric IV-monochalcogenides.

The two-dimensional ferroelectrics GeS, GeSe, SnS and SnSe are expected to have large spontaneous in-plane electric polarization and enhanced shift-current response. Using density functional methods, we show that these materials also exhibit the largest effective second harmonic generation reported so far. It can reach magnitudes up to [Formula: see text] which is about an order of magnitude larger than that of prototypical GaAs.