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Abstract Spin-orbit coupling in noncentrosymmetric crystals leads to spin-momentum locking – a directional relationship between an electron’s spin angular momentum and its linear momentum. Isotropic orthogonal Rashba spin-momentum locking has been studied for decades, while its counterpart, isotropic parallel Weyl spin-momentum locking has remained elusive in experiments. Theory predicts that Weyl spin-momentum locking can only be realized in structurally chiral cubic crystals in the vicinity of Kramers-Weyl or multifold fermions. Here, we use spin- and angle-resolved photoemission spectroscopy to evidence Weyl spin-momentum locking of multifold fermions in the chiral topological semimetal PtGa. We find that the electron spin of the Fermi arc surface states is orthogonal to their Fermi surface contour for momenta close to the projection of the bulk multifold fermion at the Γ point, which is consistent with Weyl spin-momentum locking of the latter. The direct measurement of the bulk spin texture of the multifold fermion at the R point also displays Weyl spin-momentum locking. The discovery of Weyl spin-momentum locking may lead to energy-efficient memory devices and Josephson diodes based on chiral topological semimetals.
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Data for "Gate-tunable spin texture in a Dirac semimetal-ferromagnetic semiconductor heterostructure"
Abstract: We use a concerted theory-experiment effort to investigate the formation of chiral real space spin texture when the archetypal Dirac semimetal Cd3As2 is interfaced with In1−xMnxAs, a ferromagnetic semiconductor with perpendicular magnetic anisotropy. We combine DFT calculations, the linear response theory for spin susceptibility and micromagnetic simulations to explore the possibility of chiral spin texture in this heterostructure. While a non-zero off-diagonal spin susceptibility in the Cd3As2 layer due to inversion symmetry breaking suggests the presence of Dzyaloshinskii-Moriya interaction (DMI) between local moments in the InMnAs layers, the amplitude may not be strong enough to give a “full” skyrmion texture. Instead, the interace states at the junction may promote a “partial” skyrmion texture. Using electrical magnetoresistance measurements at low temperature, we observe an emergent excess contribution to the transverse magneto-resistance whose behavior is consistent with a topological Hall effect arising from the formation of an interfacial chiral spin texture. This excess Hall voltage varies with gate voltage, indicating a promising electrostatically-tunable platform for understanding the interplay between the helical momentum space states of a Dirac semimetal and chiral real-space spin textures in a ferromagnet.
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- Award ID(s):
- 2407130
- PAR ID:
- 10698107
- Publisher / Repository:
- scholarsphere
- Date Published:
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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