Diego Mastrogiuseppe

Symmetries and hybridization in the indirect interaction between magnetic moments inMoS2nanoflakes

We study the Ruderman-Kittel-Kasuya-Yosida interaction between magnetic impurities embedded in

Kondo effect in graphene with Rashba spin-orbit coupling

p

Hybridization and anisotropy in the exchange interaction in three-dimensional Dirac semimetals

-doped transition metal dichalcogenide triangular flakes. The role of underlying symmetries is exposed by analyzing the interaction as a function of impurity separation along zigzag and armchair trajectories, in specific parts of the sample. The large spin-orbit coupling in these materials produces strongly anisotropic interactions, including a Dzyaloshinskii-Moriya component that can be sizable and tunable. We consider impurities hybridized to different orbitals of the host transition-metal and identify specific characteristics for onsite and hollow site adsorption. In the onsite case, the different components of the interaction have similar magnitude, while for the hollow site, the Ising component dominates. We also study the dependence of the interaction with the level of hole doping, which supplies a further degree of tunability. Our results could provide ways of controlling helical long range spin order in magnetic impurity arrays embedded in these materials.

Noncollinear exchange interaction in transition metal dichalcogenide edges

We study the Kondo screening of a magnetic impurity adsorbed in graphene in the presence of Rashba spin-orbit interaction. The system is described by an effective single-channel Anderson impurity model, which we analyze using the numerical renormalization group. The nontrivial energy dependence of the host density of states gives rise to interesting behaviors under variation of the chemical potential or the spin-orbit coupling. Varying the Rashba coupling produces strong changes in the Kondo temperature characterizing the many-body screening of the impurity spin, and at half filling allows an approach to a quantum phase transition separating the strong-coupling Kondo phase from a free-moment phase. Tuning the chemical potential close to sharp features of the hybridization function results in striking features in the temperature dependencies of thermodynamic quantities and in the frequency dependence of the impurity spectral function.

RKKY interaction and intervalley processes inp-doped transition-metal dichalcogenides

We study the Ruderman-Kittel-Kasuya-Yosida interaction in 3D Dirac semimetals. Using retarded Greens functions in real space, we obtain and analyze asymptotic expressions for the interaction, with magnetic impurities at different distances and relative angle with respect to high symmetry directions on the lattice. We show that the Fermi velocity anisotropy in these materials produces a strong renormalization of the magnitude of the interaction, as well as a correction to the frequency of oscillation in real space. Hybridization of the impurities to different conduction electron orbitals are shown to result in interesting anisotropic spin-spin interactions which can generate spiral spin structures in doped samples.

Microscopic theory for the incommensurate transition in TiOCl

We study the Ruderman-Kittel-Kasuya-Yosida effective exchange interaction between magnetic impurities embedded on the edges of transition-metal dichalcogenide flakes, using a three-orbital tight-binding model. Electronic states lying midgap of the bulk structure have strong one-dimensional (1D) character, localized on the edges of the crystallite. This results in exchange interactions with

Dimerization process and elementary excitations in spin?Peierls chains coupled by frustrated interactions

1/r

Quantum phase transitions into Kondo states in bilayer graphene

(or slower) decay with distance

Generation of chiral solitons in antiferromagnetic chains by a quantum quench

r

Incommensurate spin Luttinger liquid phase in a model for the spin-Peierls materials TiOBr and TiOCl

, similar to other 1D systems. Most interestingly, however, the strong spin-orbit interaction in these materials results in sizable non-collinear Dzyaloshinskii-Moriya interactions between impurities, comparable in size to the usual Ising and in-plane components. Varying the relevant Fermi energy by doping or gating may allow one to modulate the effective interactions, controlling the possible helical ground state configurations of multiple impurities.