Magnetization-dependent Rashba splitting of quantum well states at the Co/W interface

Moras, Paolo; Bihlmayer, Gustav; Sheverdyaeva, P. M.; Mahatha, S. K.; Papagno, M.; Sánchez-Barriga, J.; Rader, O.; Novinec, L.; Gardonio, Sandra; Carbone, C.

doi:10.1103/physrevb.91.195410

Cited by 25 publications

(23 citation statements)

References 39 publications

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“…Up to now, k-resolved experimental observations of the magnetization-related changes of the electronic band structure of a ferromagnetic film were reported only for surface-or interface-related electronic states such as the surface state of oxidized Gd(0001) [48] or quantum well states in Co/W(110) [49]. In these works, the observed effect was interpreted in relation to the so-called Rashba term [50,51] in the total Hamiltonian of the system.…”

Section: Resultsmentioning

confidence: 99%

Fermi Surface Manipulation by External Magnetic Field Demonstrated for a Prototypical Ferromagnet

et al. 2016

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We consider the details of the near-surface electronic band structure of a prototypical ferromagnet, Fe(001). Using high-resolution angle-resolved photoemission spectroscopy, we demonstrate openings of the spin-orbit-induced electronic band gaps near the Fermi level. The band gaps, and thus the Fermi surface, can be manipulated by changing the remanent magnetization direction. The effect is of the order of ΔE ¼ 100 meV and Δk ¼ 0.1 Å −1 . We show that the observed dispersions are dominated by the bulk band structure. First-principles calculations and one-step photoemission calculations suggest that the effect is related to changes in the electronic ground state and not caused by the photoemission process itself. The symmetry of the effect indicates that the observed electronic bulk states are influenced by the presence of the surface, which might be understood as related to a Rashba-type effect. By pinpointing the regions in the electronic band structure where the switchable band gaps occur, we demonstrate the significance of spinorbit interaction even for elements as light as 3d ferromagnets. These results set a new paradigm for the investigations of spin-orbit effects in the spintronic materials. The same methodology could be used in the bottom-up design of the devices based on the switching of spin-orbit gaps such as electric-field control of magnetic anisotropy or tunneling anisotropic magnetoresistance.

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Section: Resultsmentioning

confidence: 99%

Fermi Surface Manipulation by External Magnetic Field Demonstrated for a Prototypical Ferromagnet

et al. 2016

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“…For example, very recent experiments [14][15][16] have replaced HM with threedimensional topological insulators (3D TIs) [17]. The TIs enhance [18][19][20] (by a factor v F /α R , where v F is the Fermi velocity on the surface of TI and α R is the Rashba SOC strength [21,22] at the F/HM interface) the transverse nonequilibrium spin density driven by the longitudinal charge current, which is responsible for the large fieldlike SOT component [20,23] observed experimentally [14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Antidamping spin-orbit torque driven by spin-flip reflection mechanism on the surface of a topological insulator: A time-dependent nonequilibrium Green function approach

2016

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Motivated by recent experiments observing spin-orbit torque (SOT) acting on the magnetization m of a ferromagnetic (F) overlayer on the surface of a three-dimensional topological insulator (TI), we investigate the origin of the SOT and the magnetization dynamics in such systems. We predict that lateral F/TI bilayers of finite length, sandwiched between two normal metal leads, will generate a large anti-damping-like SOT per very low charge current injected parallel to the interface. The large values of anti-damping-like SOT are spatially localized around the transverse edges of the F overlayer. Our analysis is based on adiabatic expansion (to first order in ∂ m/∂t) of time-dependent nonequilibrium Green functions (NEGFs), describing electrons pushed out of equilibrium both by the applied bias voltage and by the slow variation of a classical degree of freedom [such as m(t)]. From it we extract formulas for spin torque and charge pumping, which show that they are reciprocal effects to each other, as well as Gilbert damping in the presence of SO coupling. The NEGF-based formula for SOT naturally splits into four components, determined by their behavior (even or odd) under the time and bias voltage reversal. Their complex angular dependence is delineated and employed within Landau-Lifshitz-Gilbert simulations of magnetization dynamics in order to demonstrate capability of the predicted SOT to efficiently switch m of a perpendicularly magnetized F overlayer.

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“…Indeed, these states are difficult to resolve when the film thickness exceeds a few monolayers, due to the overlap of narrow d-bands with different symmetry. Nevertheless, the k || -dependent dispersion of d-like QW states has been recently determined by ARPES on relatively thick Co [29] and Fe [30] films.…”

Section: Introductionmentioning

confidence: 99%

Energy-momentum mapping ofd-derived Au(111) states in a thin film

et al. 2016

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The quantum well states of a film can be used to sample the electronic structure of the parent bulk material and determine its band parameters. We highlight the benefits of two-dimensional film band mapping, with respect to complex bulk analysis, in an angle-resolved photoemission spectroscopy study of the 5d states of Au(111). Discrete 5d-derived quantum well states of various orbital characters form in Au (111)

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Magnetization-dependent Rashba splitting of quantum well states at the Co/W interface

Cited by 25 publications

References 39 publications

Fermi Surface Manipulation by External Magnetic Field Demonstrated for a Prototypical Ferromagnet

Fermi Surface Manipulation by External Magnetic Field Demonstrated for a Prototypical Ferromagnet

Antidamping spin-orbit torque driven by spin-flip reflection mechanism on the surface of a topological insulator: A time-dependent nonequilibrium Green function approach

Energy-momentum mapping ofd-derived Au(111) states in a thin film

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