Artem Abanov

Skyrmion in a real magnetic film

Skyrmions are the magnetic defects in an ultrathin magnetic film, similar to the bubble domains in the thicker films. Even weak uniaxial anisotropy determines its radius unambiguously. We consider the dynamics of the skyrmion decay. We show that the discreteness of the lattice in an isotropic 2D magnet leads to a slow rotation of the local magnetization in the skyrmion and, provided a small dissipation, to decay of the skyrmion. The radius of such a skyrmion as a function of time is calculated. We prove that uniaxial anisotropy stabilizes the skyrmion and study the relaxation process.

Skyrmion production on demand by homogeneous DC currents

Topological magnetic textures - like skyrmions - have become a major player in the design of next-generation magnetic storage technology due to their stability and the control of their motion by ultra-low current densities. A major challenge to develop this new skyrmion-based technology is to achieve the controlled and deterministic creation of magnetic skyrmions without the need of complex setups. We demonstrate a solution to this challenge by showing how to create skyrmions and other magnetic textures in ferromagnetic thin films by means of a homogeneous DC current and without requiring Dzyaloshinskii-Moriya interactions. This is possible by exploiting a static loss of stability arising from the interplay of current-induced spin-transfer torque and a spatially inhomogeneous magnetization, which can be achieved, e.g., by locally engineering the anisotropy, the magnetic field, or other magnetic interactions. The magnetic textures are created controllably, efficiently, and periodically with a period that can be tuned by the applied current strength. We propose specific experimental setups realizable with simple materials, such as cobalt based materials, to observe the periodic formation of skyrmions. We show that adding chiral interactions will not influence the basics of the generations but then influence the consequent dynamics with respect to the stabilization of topological textures. Our findings allow for the production of skyrmions on demand in simple ferromagnetic thin films by homogeneous DC currents.

Stable path to ferromagnetic hydrogenated graphene growth

In this paper, we propose a practical way to stabilize half-hydrogenated graphene (graphone). We show that the dipole moments induced by a hexagonal-boron nitride (h-BN) substrate on graphene stabilize the hydrogen atoms on one sublattice of the graphene layer and suppress the migration of the adsorbed hydrogen atoms. Based upon first principle spin polarized density of states calculations, we show that the graphone obtained in different graphene/h-BN heterostructures exhibits a half metallic state. We propose to use this exotic material for spin valve systems and other spintronics devices.

Superconductivity near a Quantum-Critical Point: The Special Role of the First Matsubara Frequency

Near a quantum-critical point in a metal strong fermion-fermion interaction mediated by a soft collective boson gives rise to incoherent, non-Fermi liquid behavior. It also often gives rise to superconductivity which masks the non-Fermi liquid behavior. We analyze the interplay between the tendency to pairing and fermionic incoherence for a set of quantum-critical models with effective dynamical interaction between low-energy fermions. We argue that superconducting T_{c} is nonzero even for strong incoherence and/or weak interaction due to the fact that the self-energy from dynamic critical fluctuations vanishes for the two lowest fermionic Matsubara frequencies ω_{m}=±πT. We obtain the analytic formula for T_{c}, which reproduces well earlier numerical results for the electron-phonon model at vanishing Debye frequency.

Continuous Néel-to-Bloch transition in strips whose thickness increases: Statics and dynamics

For strips of width 2w and height h, with both exchange and the dipole-dipole interaction, we find that Neel and Bloch domain walls are locally stable. As h is increased to hc, Neel walls evolve continuously to Bloch walls by a second-order transition. It is mediated by a critical mode with , corresponding to motion of the domain wall center. A uniform out-of-plane rf-field couples strongly to this critical mode only in the Neel phase. Local, but not global stability relative to a crosstie phase was established.

Reduced effect of impurities on the universal pairing scale in the cuprates

We consider the effect of non-magnetic impurities on the onset temperature

Long-wavelength anomalous diffusion mode in the two-dimensional XY dipole magnet

T^*

Phase diagram of ultrathin ferromagnetic films with perpendicular anisotropy

for the

Current-driven periodic domain wall creation in ferromagnetic nanowires

d-

Lateral hydrogenated graphene/h-BN Tunneling Magnetoresistance Devices

wave pairing in spin-fluctuation scenario for the cuprates. We analyze intermediate coupling regime when the magnetic correlation length