Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userMetastable solitonic states in the strained itinerant helimagnet FeGe
96
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The tensile strain is a promising tool for creation and manipulation of magnetic solitonic textures in the chiral helimagnets via tunable control of magnetic anisotropy and Dzyaloshinskii-Moriya interaction. Here, by using the in-situ resonant small-angle x-ray scattering we demonstrate that the skyrmion and chiral soliton lattices can be achieved as metastable states in FeGe lamella as distinct states or even simultaneously by combining the tensile strain and magnetic fields in various orientations with respect to the deformation. The small-angle scattering data are discussed in the frame of the analytical model which is sufficient to describe the experimental results for soliton lattice. By using the experimental results and analytical theory, unwinding of the metastable skyrmions in the perpendicular magnetic field as seen by small-angle scattering experiment was analyzed by the micromagnetic simulation.
rate research
Read More
Chiral magnetic interactions induce complex spin textures including helical and conical spin waves, as well as particle-like objects such as magnetic skyrmions and merons. These spin textures are the basis for innovative device paradigms and give rise to exotic topological phenomena, thus being of interest for both applied and fundamental sciences. Present key questions address the dynamics of the spin system and emergent topological defects. Here we analyze the micromagnetic dynamics in the helimagnetic phase of FeGe. By combining magnetic force microscopy, single-spin magnetometry, and Landau-Lifschitz-Gilbert simulations we show that the nanoscale dynamics are governed by the depinning and subsequent motion of magnetic edge dislocations. The motion of these topologically stable objects triggers perturbations that can propagate over mesoscopic length scales. The observation of stochastic instabilities in the micromagnetic structure provides new insight to the spatio-temporal dynamics of itinerant helimagnets and topological defects, and discloses novel challenges regarding their technological usage.
Memory or transistor devices based on electrons spin rather than its charge degree of freedom offer certain distinct advantages and comprise a cornerstone of spintronics. Recent years have witnessed the emergence of a new field, valleytronics, which seeks to exploit electrons valley index rather than its spin. An important component in this quest would be the ability to control the valley index in a convenient fashion. Here we show that the valley polarization can be switched from zero to one by a small reduction in density, simply tuned by a gate bias, in a two-dimensional electron system. This phenomenon arises fundamentally as a result of electron-electron interaction in an itinerant, dilute electron system. Essentially, the kinetic energy favors an equal distribution of electrons over the available valleys, whereas the interaction between electrons prefers single-valley occupancy below a critical density. The gate-bias-tuned transition we observe is accompanied by a sudden, two-fold change in sample resistance, making the phenomenon of interest for potential valleytronic transistor device applications. Our observation constitutes a quintessential demonstration of valleytronics in a very simple experiment.
We have studied the electronic structure of hexagonal MnAs, as epitaxial continuous film on GaAs(001) and as nanocrystals embedded in GaAs, by Mn 2p core-level photoemission spectroscopy. Configuration-interaction analyses based on a cluster model show that the ground state of the embedded MnAs nanocrystals is dominated by a d5 configuration that maximizes the local Mn moment. Nanoscaling and strain significantly alter the properties of MnAs. Internal strain in the nanocrystals results in reduced p-d hybridization and enhanced ionic character of the Mn-As bonding interactions. The spatial confinement and reduced p-d hybridization in the nanocrystals lead to enhanced d-electron localization, triggering d-d electron correlations and enhancing local Mn moments. These changes in the electronic structure of MnAs have an advantageous effect on the Curie temperature of the nanocrystals, which is measured to be remarkably higher than that of bulk MnAs.
The non-trivial topology of the three-dimensional (3D) topological insulator (TI) dictates the appearance of gapless Dirac surface states. Intriguingly, when a 3D TI is made into a nanowire, a gap opens at the Dirac point due to the quantum confinement, leading to a peculiar Dirac sub-band structure. This gap is useful for, e.g., future Majorana qubits based on TIs. Furthermore, these Dirac sub-bands can be manipulated by a magnetic flux and are an ideal platform for generating stable Majorana zero modes (MZMs), which play a key role in topological quantum computing. However, direct evidence for the Dirac sub-bands in TI nanowires has not been reported so far. Here we show that by growing very thin ($sim$40-nm diameter) nanowires of the bulk-insulating topological insulator (Bi$_{1-x}$Sb$_x$)$_2$Te$_3$ and by tuning its chemical potential across the Dirac point with gating, one can unambiguously identify the Dirac sub-band structure. Specifically, the resistance measured on gate-tunable four-terminal devices was found to present non-equidistant peaks as a function of the gate voltage, which we theoretically show to be the unique signature of the quantum-confined Dirac surface states. These TI nanowires open the way to address the topological mesoscopic physics, and eventually the Majorana physics when proximitised by an $s$-wave superconductor.
When twisted to angles near 1{deg}, graphene multilayers provide a new window on electron correlation physics by hosting gate-tuneable strongly-correlated states, including insulators, superconductors, and unusual magnets. Here we report the discovery of a new member of the family, density-wave states, in double bilayer graphene twisted to 2.37{deg}. At this angle the moire states retain much of their isolated bilayer character, allowing their bilayer projections to be separately controlled by gates. We use this property to generate an energetic overlap between narrow isolated electron and hole bands with good nesting properties. Our measurements reveal the formation of ordered states with reconstructed Fermi surfaces, consistent with density-wave states, for equal electron and hole densities. These states can be tuned without introducing chemical dopants, thus opening the door to a new class of fundamental studies of density-waves and their interplay with superconductivity and other types of order, a central issue in quantum matter physics.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
