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A detailed understanding of the origin of the magnetism in dilute magnetic semiconductors is crucial to their development for applications. Using hard X-ray angle-resolved photoemission (HARPES) at 3.2 keV, we investigate the bulk electronic structure of the prototypical dilute magnetic semiconductor Ga 0.97 Mn 0.03 As, and the reference undoped GaAs. The data are compared to theory based on the coherent potential approximation and fully relativistic one-step-model photoemission calculations including matrix-element effects. Distinct differences are found between angle-resolved, as well as angle-integrated, valence spectra of Ga 0.97 Mn 0.03 As and GaAs, and these are in good agreement with theory. Direct observation of Mn-induced states between the GaAs valence-band maximum and the Fermi level, centred about 400 meV below this level, as well as changes throughout the full valence-level energy range, indicates that ferromagnetism in Ga 1− x Mn x As must be considered to arise from both p – d exchange and double exchange, thus providing a more unifying picture of this controversial material. The origin of the magnetism in manganese-doped gallium arsenide has been the subject of much debate. Now, hard X-ray angle-resolved photoemission has been used to probe the electronic structure of this material and clarify the mechanism through which the magnetism arises.

Many properties of real materials can be modeled using ab initio methods within a single-particle picture. However, for an accurate theoretical treatment of excited states, it is necessary to describe electron-electron correlations including interactions with bosons: phonons, plasmons, or magnons. In this work, by comparing spin- and momentum-resolved photoemission spectroscopy measurements to many-body calculations carried out with a newly developed first-principles method, we show that a kink in the electronic band dispersion of a ferromagnetic material can occur at much deeper binding energies than expected ( E b  = 1.5 eV). We demonstrate that the observed spectral signature reflects the formation of a many-body state that includes a photohole bound to a coherent superposition of renormalized spin-flip excitations. The existence of such a many-body state sheds new light on the physics of the electron-magnon interaction which is essential in fields such as spintronics and Fe-based superconductivity. The conduction electron and magnon interactions are essential for the understanding and development of spintronics and superconductivity. Here the authors show a deep binding energy kink in spin-resolved photoemission spectra which is understood as a signature the many-body spin flip excitation in Fe single crystal thin film.

Traditional ultraviolet/soft X-ray angle-resolved photoemission spectroscopy (ARPES) may in some cases be too strongly influenced by surface effects to be a useful probe of bulk electronic structure. Going to hard X-ray photon energies and thus larger electron inelastic mean-free paths should provide a more accurate picture of bulk electronic structure. We present experimental data for hard X-ray ARPES (HARPES) at energies of 3.2 and 6.0 keV. The systems discussed are W, as a model transition-metal system to illustrate basic principles, and GaAs, as a technologically-relevant material to illustrate the potential broad applicability of this new technique. We have investigated the effects of photon wave vector on wave vector conservation, and assessed methods for the removal of phonon-associated smearing of features and photoelectron diffraction effects. The experimental results are compared to free-electron final-state model calculations and to more precise one-step photoemission theory including matrix element effects. Angle-resolved photoemission spectroscopy is possibly the most widely used technique to probe the electronic structure of crystals. Unfortunately the technique is usually too sensitive to surface properties. It is now demonstrated that by using hard X-rays as the incident radiation it is possible to probe the electronic structure in the bulk.

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=100meV and Δk=0.1Å−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 spin-orbit 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.

A detailed understanding of the origin of the magnetism in dilute magnetic semiconductors is crucial to their development for applications. Using hard X-ray angle-resolved photoemission (HARPES) at 3.2 keV, we investigate the bulk electronic structure of the prototypical dilute magnetic semiconductor Ga(0.97)Mn(0.03)As, and the reference undoped GaAs. The data are compared to theory based on the coherent potential approximation and fully relativistic one-step-model photoemission calculations including matrix-element effects. Distinct differences are found between angle-resolved, as well as angle-integrated, valence spectra of Ga(0.97)Mn(0.03)As and GaAs, and these are in good agreement with theory. Direct observation of Mn-induced states between the GaAs valence-band maximum and the Fermi level, centred about 400 meV below this level, as well as changes throughout the full valence-level energy range, indicates that ferromagnetism in Ga(1-x)Mn(x)As must be considered to arise from both p-d exchange and double exchange, thus providing a more unifying picture of this controversial material.

A detailed understanding of the origin of the magnetism in dilute magnetic semiconductors is crucial to their development for applications. Using hard X-ray angle-resolved photoemission (HARPES) at 3.2keV, we investigate the bulk electronic structure of the prototypical dilute magnetic semiconductor Ga sub(0.97)Mn sub(0.03)As, and the reference undoped GaAs. The data are compared to theory based on the coherent potential approximation and fully relativistic one-step-model photoemission calculations including matrix-element effects. Distinct differences are found between angle-resolved, as well as angle-integrated, valence spectra of Ga sub(0.97)Mn sub(0.03)As and GaAs, and these are in good agreement with theory. Direct observation of Mn-induced states between the GaAs valence-band maximum and the Fermi level, centred about 400meV below this level, as well as changes throughout the full valence-level energy range, indicates that ferromagnetism in Ga sub(1-x)Mn sub(x)As must be considered to arise from both p-d exchange and double exchange, thus providing a more unifying picture of this controversial material.

Spin- and orbital-resolved access to the electronic bands is necessary to establish key properties of quantum materials such as the quantum-geometric tensor. Despite recent revival on magnetic Kagome compounds, no spectroscopic access to their magnetic properties has been available so far due to small domain sizes and lack of appropriate techniques. Furthermore, their real space magnetic texture is often complex and temperature-dependent. We investigate the magnetic Kagome metal DyMn\\(_6\\)Sn\\(_6\\) using high-resolution micro-focused circular-dichroic angle-resolved photoemission (\\(\\mu\\)-CD-ARPES) to probe its magnetic and electronic properties. By tuning the kinetic energy to various features of the Dy \\(4f\\) multiplet, we resolve magnetic domains in samples cryo-cooled down to 20 K. Smaller, but clear signatures are detected in the Mn \\(3p\\) levels. The behavior of both Dy \\(4f\\) and Mn \\(3p\\) features are in remarkable agreement with our modeling based on the Hartree-Fock method, revealing ferrimagnetic alignment of Dy and Mn local moments, and further strengthening our interpretation. Adjusting the energy to the Mn \\(3d\\)-dominated valence bands reveals signatures which we relate to the orbital magnetization through a comparison to {\\it ab initio} electronic structure calculations. Our study establishes the spectroscopic access to a single magnetic domain in a Kagome metal, paving the way for further research into imaging magnetic phases of novel magnetic materials using \\(\\mu\\)-CD-ARPES.

We visualize the topological ladder and band inversions in PtTe\\(_2\\) using spin-polarized photoemission spectroscopy augmented by three-dimensional momentum imaging. This approach enables the detection of spin polarization in dispersive bands and provides access to topological properties beyond the reach of conventional methods. Extensive mapping of spin-momentum space reveals distinct topological surface states, including a surface Dirac cone at the binding energy \\(E_B \\sim 2.3\\) eV and additional states at \\(E_B \\sim 1.6\\) eV, \\(E_B \\sim 1.0\\) eV, and near the Fermi level. The electronic structure analysis demonstrates strong hybridization between Pt and Te atomic orbitals, confirming the nontrivial topology of these surface states. Furthermore, by comparison to one-step model photoemission calculations, we identify a robust correlation between the initial-state and measured spin polarizations while revealing asymmetries in specific experimental spin textures. These asymmetries, absent in the initial states due to symmetry constraints, arise from the breaking of time-reversal symmetry during the photoemission process, emphasizing the crucial influence of symmetries on experimental signatures of topology.

Among antiferromagnetic materials, Mn\\(_2\\)Au is one of the most intensively studied, and it serves as a very popular platform for testing various ideas related to antiferromagnetic magnetotransport and dynamics. Since recently, this material has also attracted considerable interest in the context of optical properties and optically-driven antiferromagnetic switching. In this work, we use first principles methods to explore the physics of charge photocurrents, spin photocurrents and inverse Faraday effect in antiferromagnetic Mn\\(_2\\)Au. We predict the symmetry and magnitude of these effects, and speculate that they can be used for tracking the dynamics of staggered moments during switching. Our calculations reveal the emergence of large photocurrents of spin in collinear Mn\\(_2\\)Au, whose properties can be understood as a result of a non-linear optical version of spin Hall effect \\(-\\) which we refer to as the \\(\\textit{photospin Hall effect}\\) encoded into the relation between the driving charge and resulting spin photocurrents. Moreover, we suggest that even a very small canting in Mn\\(_2\\)Au can give rise to colossal spin photocurrents which are \\(\\textit{chiral}\\) in flavor. We conclude that the combination of staggered magnetization with the structural and electronic properties of this material results in a unique blend of prominent photocurrents, which makes Mn\\(_2\\)Au a unique platform for advanced optospintronics applications.

In the realm of two-dimensional materials magnetic and transport properties of a unique representative \\(-\\) Fe\\(_3\\)GeTe\\(_2\\) \\(-\\) attract ever increasing attention. Here, we use a developed first-principles method for calculating laser-induced response to study the emergence of photo-induced currents of charge and spin in single-layer Fe\\(_3\\)GeTe\\(_2\\), which are of second order in the electric field. We provide a symmetry analysis of the emergent photocurrents in the system finding it to be in excellent agreement with ab-initio calculations. We analyse the magnitude and behavior of the charge photocurrents with respect to disorder strength, frequency and band filling. Remarkably, not only do we find a large charge current response, but also predict that Fe\\(_3\\)GeTe\\(_2\\) can serve as a source of significant laser-induced spin-currents, which makes this material as a promising platform for various applications in optospintronics.