Textures of Spin-Orbit Coupled F=2 Spinor Bose Einstein Condensates

We study the textures of F=2 spinor Bose-Einstein condensates (BECs) with spin-orbit coupling (SOC) induced by a synthetic non-Abelian gauge field. On the basis of the analysis of the SOC energy and the numerical calculation of the Gross-Pitaevskii equation, we demonstrate that the textures originate from the helical modulation of the order parameter (OP) due to the SOC. In particular, the cyclic OP consists of two-dimensional lattice textures, such as the hexagonal lattice and the 1/3-vortex lattice, commonly understandable as the two-dimensional network of the helical modulations.Comment: 5 pages, 5 figure

Perpendicular electronic transport and moir\'{e}-induced resonance in twisted interfaces of 3D graphite

We calculate the perpendicular electrical conductivity in twisted three-dimensional graphite (rotationally-stacked graphite pieces) by using the effective continuum model and the recursive Green's function method. In the low twist angle regime $(\theta \lesssim 2^\circ)$, the conductivity shows a non-monotonous dependence with a peak and dip structure as a function of the twist angle. By analyzing the momentum-resolved conductance and the local density of states, this behavior is attributed to the Fano resonance between continuum states of bulk graphite and interface-localized states, which is a remnant of the flat band in the magic-angle twisted bilayer graphene. We also apply the formulation to the high-angle regime near the commensurate angle $\theta \approx 21.8^\circ$, and reproduce the conductance peak observed in the experiment.Comment: 15 pages, 13 figure

Topological Domain Walls in Graphene Nanoribbons with Carrier Doping

We theoretically study magnetic ground states of doped zigzag graphene nanoribbons and the emergence of topological domain walls. Using the Hartree-Fock mean-field approach and an effective continuum model, we demonstrated that the carrier doping stabilizes a magnetic structure with alternating antiferromagnetic domains, where the doped carriers are accommodated in topological bound states localized at the domain wall. The energy spectrum exhibits a Hofstadter-like fractal spectral evolution as a function of the carrier density, where minigaps are characterized by the Chern number associated with the adiabatic charge pump in moving domain walls. A systematic analysis for nanoribbons with different widths revealed that the ferromagnetic domain-wall phase emerges in relatively wide ribbons, while the colinear domain-wall phase arises in narrower ribbons.Comment: 14 pages, 11 figure

Mechanical properties of 2D metal-organic and covalent-organic frameworks with non trivial topological band dispersion

Using density functional theory (DFT), we investigate mechanical properties of a few 2D metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs) having Dirac and flat bands. These porous materials have become a subject of great captivation because of their physical stability, distinctive structural characteristics and large surface to volume ratio. The inherent porosity of these frameworks gives rise to many fascinating and occasionally surprising phenomena, which makes them potential candidates for technological applications. For reliable usage of MOFs/COFs in functional nanodevice and practical application, it is quite imperative to investigate their mechanical properties. Thus, herein a particular attention is paid to study elastic deformation of few 2D MOFs and COFs having non trivial topological band dispersion in the regime with linear dependency of stress upon strain. Specially, we consider different types of deformation and find all the components of elastic tensor from the stress-strain and energy-strain curves. These findings may provide useful information to fabricate the MOFs/COFs based devices by lowering the number of experiments.Comment: 26 Pages, 9 figure