arXiv subjects

C. Śliwa

Publications and source records attributed to C. Śliwa.

3 recordsLinked to original sources

arXiv2023

Quantum transport and mobility spectrum of topological carriers in (001) SnTe/PbTe heterojunctions

Measurements of magnetotransport in SnTe/PbTe heterojunctions grown by the MBE technique on (001) undoped CdTe substrates were performed. At low magnetic fields, quantum corrections to conductivity were observed that may be attributed to the presence of topological states at the junction interface. For a sample with 5 nm thick SnTe layer, the data analysis suggests that midgap states are actually gapped. However, the phase coherence effects in 10 nm and 20 nm SnTe/PbTe samples are fully explained assuming existence of gapless Dirac cones. Magnetotransport at higher magnetic fields is described in the framework of mobility spectrum analysis (MSA). We demonstrate that the electron- and hole-like peaks observed simultaneously for all SnTe/PbTe heterojunctions may originate from the concave and convex parts of the energy isosurface for topological states -- and not from the existence of quasiparticles both carrying negative and positive charges. This interpretation is supported by numerical calculations of conductivity tensor components for gapless (100) Dirac cones, performed within a classical model and based on the solutions of Boltzmann transport equation. Our approach shows the feasibility of MSA in application to magnetotransport measurements on topological matter.

cond-mat.mes-hall↗

arXiv2017

Energetic, electronic and magnetic properties of Mn-dimers on reconstructed (001) GaAs surfaces

We study energetic, magnetic, and electronic properties of diluted substitutional Mn-pairs on the reconstructed $(001)$ GaAs surfaces. The studies are based on first-principles calculations in the framework of the density functional theory. We demonstrate that the stability of the systems strongly depends on the position, orientation, and the distance between the Mn-atoms constituting the pair. Independently of the considered surface reconstruction pattern, the Mn-pairs with Mn-atoms being the nearest neighbors (NN) on cationic sublattice turn out to be energetically more favorable than the pairs with the larger distance between the Mn-atoms. However, the preferential build-up orientation of the Mn-NN-pair depends on the surface reconstruction and is parallel either to $[110]$ or $[1\bar{1}0]$ crystallographic direction. We reveal also the mechanisms of the magnetic ordering of Mn-NN-pairs. The Mn-NN-pairs along the $[110]$ crystallographic direction exhibit always ferromagnetic alignment of Mn spins, whereas the spins in the Mn-NN-pairs along $[1\bar{1}0]$ direction are mostly anti-ferromagnetically aligned. In the electronic structure of the systems containing Mn-pairs with ferromagnetically aligned spins, we observe the valence band hole states in the neighborhood of Fermi energy. This indicates that the surface ferromagnetism in this prototype of dilute magnetic semiconductors can be explained in terms of the $p$-$d$ Zener model.

cond-mat.mtrl-sci↗

arXiv2002

Charge Superselection Sectors for Scalar QED on the Lattice

The lattice model of scalar quantum electrodynamics (Maxwell field coupled to a complex scalar field) in the Hamiltonian framework is discussed. It is shown that the algebra of observables ${\cal O}(Λ)$ of this model is a $C^*$-algebra, generated by a set of gauge-invariant elements satisfying the Gauss law and some additional relations. Next, the faithful, irreducible and non-degenerate representations of ${\cal O}(Λ)$ are found. They are labeled by the value of the total electric charge, leading to a decomposition of the physical Hilbert space into charge superselection sectors. In the Appendices we give a unified description of spinorial and scalar quantum electrodynamics and, as a byproduct, we present an interesting example of weakly commuting operators, which do not commute strongly.

hep-th↗