Abstract
There has been increasing interest in materials where relativistic effects induce non-trivial electronic states with promise for spintronics applications. One example is the splitting of bands with opposite spin chirality produced by the Rashba spin-orbit coupling in asymmetric potentials. Sizable splittings have been hitherto obtained using either heavy elements, where this coupling is intrinsically strong, or large surface electric fields. Here by means of angular resolved photoemission spectroscopy and first-principles calculations, we give evidence of a large Rashba coupling of 0.25 eV Å, leading to a remarkable band splitting up to 0.15 eV with hidden spin-chiral polarization in centrosymmetric BaNiS2. This is explained by a huge staggered crystal field of 1.4 V Å−1, produced by a gliding plane symmetry, that breaks inversion symmetry at the Ni site. This unexpected result in the absence of heavy elements demonstrates an effective mechanism of Rashba coupling amplification that may foster spin-orbit band engineering.
Highlights
There has been increasing interest in materials where relativistic effects induce non-trivial electronic states with promise for spintronics applications
The Rashba Hamiltonian, H^ R 1⁄4 aR^z Á r^Âk^ 1⁄4 bE Á r^Âk, where aR and b are constants and r^ is the spin vector operator composed of the Pauli matrices s^x, s^y and s^z, requires an electric field E 1⁄4 Ez^z that breaks the inversion symmetry along the z-direction perpendicular to the plane containing the spin r and the electron wave vector k
To the best of our knowledge, the experimental band structure is not available for BaNiS2 and first-principles calculations have been hitherto limited to a simple density functional theory (DFT) approach in the local density approximation neglecting the Hubbard repulsion term, U, and relativistic SO effects[19,20]
Summary
There has been increasing interest in materials where relativistic effects induce non-trivial electronic states with promise for spintronics applications. By means of angular resolved photoemission spectroscopy and first-principles calculations, we give evidence of a large Rashba coupling of 0.25 eVÅ, leading to a remarkable band splitting up to 0.15 eV with hidden spin-chiral polarization in centrosymmetric BaNiS2 This is explained by a huge staggered crystal field of 1.4 VÅ À 1, produced by a gliding plane symmetry, that breaks inversion symmetry at the Ni site. By means of angular-resolved photoemission spectroscopy (ARPES) on high-quality single crystals, we find a very large Rashba splitting up to DeE150 meV, which is unexpected in a centrosymmetric system without electronically active heavy elements This observation is explained by a very effective LIA mechanism associated with a peculiar non-symmorphic square-pyramidal structure with a gliding plane symmetry. The mechanism unveiled by the present results, opens new possibilities to tune effectively the topological order of solids without the constraint of using either heavy elements or external fields
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