Abstract
In non-magnetic materials the combination of inversion symmetry breaking (ISB) and spin-orbit coupling (SOC) determines the spin polarization of the band structure. However, a local spin polarization can also arise in centrosymmetric crystals containing ISB subunits. This is namely the case for the nodal-line semimetal ZrSiTe where, by combining spin- and angle-resolved photoelectron spectroscopy with ab initio band structure calculations, we reveal a complex spin polarization. In the bulk, the valence and conduction bands exhibit opposite spin orientations in two spatially separated two-dimensional ZrTe sectors within the unit cell, yielding no net polarization. We also observe spin-polarized surface states that are well separated in energy and momentum from the bulk bands. A layer-by-layer analysis of the spin polarization allows us to unveil the complex evolution of the signal in the bulk states near the surface, thus bringing the intertwined nature of surface and bulk effects to the fore.
Highlights
In non-magnetic materials the combination of inversion symmetry breaking (ISB) and spinorbit coupling (SOC) determines the spin polarization of the band structure
ZrSiTe exhibits surface states that are well separated in energy and momentum from the bulk bands[24], and we find that these surface states are spin polarized
Owing to the local breaking of inversion symmetry, and under the action of SOC, the bands can acquire a local hidden spin polarization, as we show
Summary
In non-magnetic materials the combination of inversion symmetry breaking (ISB) and spinorbit coupling (SOC) determines the spin polarization of the band structure. Those results have established the concept of hidden spin polarization in CS materials, but questions about the relative importance of the local site asymmetry vs the surface SIA in determining the bulk polarization remain open. The crystal structure of ZrSiTe is CS, but contains polar sites with a local electric dipole field (Fig. 2).
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