Condensed Matter Physics

One-dimensional Rashba states with unconventional spin texture in Bi chains

Spin-polarized electrons confined in low-dimensional structures are of high interest for spintronics applications. Here, we investigate the electronic structure of an ordered array of Bi monomer and dimer chains on the Ag(110) surface. By means of spin-resolved photoemission spectroscopy, we find Rashba-Bychkov split bands crossing the Fermi level with one-dimensional constant energy contours. These bands are up-spin polarized for positive wave vectors and down-spin polarized for negative wave vectors, at variance with the Rashba-Bychkov model that predicts a pair of states with opposite spin in each half of the surface Brillouin zone. Density functional theory shows that spin-selective hybridization with the Ag bulk bands originates this unconventional spin texture.

Gd induced modifications in the magnetocaloric properties of dysprosium manganites

We report structural, electronic, magnetic, and magnetocaloric studies of polycrystalline DyMnO3 and its A-site Gd substituents, Dy1−xGdxMnO3, where 0 ≤ x ≤ 1. Detailed comparison of various magnetocaloric
parameters shows that Dy0.5Gd0.5MnO3 has the best values with a large isothermal magnetic entropy change,Sm max ~ 15.35 J/kg K, adiabatic temperature change,Tad max ~ 6.15 K and relative cooling power, RCP ~ 307 J/kg, suggesting that rare earth mixing plays a vital role in enhancing the magnetocaloric properties. In addition, absence of magnetic and thermal hysteresis also makes it one of the best candidates for magnetic refrigeration among all known potential candidates for cryogenic temperature applications.

Probing the Electronic Structure of Hybrid Perovskites in the Orientationally Disordered Cubic Phase

Hybrid organic–inorganic lead halide perovskites are projected as new generation photovoltaic and optoelectronic materials with improved efficiencies. However, their electronic structure so far remains poorly understood, particularly in the orientationally disordered cubic phase. We performed electronic structure investigations using angle-resolved photoemission spectroscopy on two prototypical samples (MAPbBr3 and MAPbCl3) in their cubic phase, and the results are compared with the calculations within two theoretical models where MA+ is orientationally (1) disordered (MA+ ion is replaced by spherically symmetric Cs+ ion) and (2) ordered (MA oriented along (100) direction) but keeping the symmetry of the unit cell cubic. Degeneracy of the valence bands and behavior of constant energy contours are consistent with model 1, which supports strongly the disordered nature of the orientation of the MA+ ions in the cubic phase. Band structure calculations also reveal that spin–orbit coupling induced Rashba splitting is suppressed by the orientational disorder.