Authors: Vladimir M. Fomin | V. Kagalovsky
Source: physica status solidi (RRL) - Rapid Research Letters (article, 2023-11-01)
Field: Chemistry — Physical and Theoretical Chemistry

Topological and Geometrical Effects in Complex Nanostructures The present Special Issue represents a vividly developing realm of nanophysics: investigations of novel electronic, magnetic, optical, and transport properties of nanostructures with complex geometry and non-trivial topology emerging due to the modern advances in high-tech fabrication techniques. This topical scope was reflected at the Mini-Colloquium “Topological and geometrical effects in complex nanostructures”, organized by Vladimir M. Fomin and Feodor V. Kusmartsev in the framework of the 29th General Conference of the Condensed Matter Division of the European Physical Society in conjunction with the Institute of Physics, which took place from 21 to 26 August 2022 in Manchester, UK. The present Special Issue (partly reflecting the contributions to the Mini-Colloquium) exhibits diverse ongoing experimental and theoretical efforts toward understanding and engineering of properties of complex nanostructures, which open unprecedented potentialities for the design, functionalization, and integration of nanodevices. Arsen Herasymchuk, Sergei Sharapov, and Valery Gusynin [article number 2300084] studied the edge states in a finite-width graphene ribbon and a semi-infinite geometry in the presence of a perpendicular magnetic field and an in-plane electric field applied perpendicular to a zigzag edge. They considered both gapless and gapped Dirac fermions using analytic and numerical methods within the framework of low-energy effective theory. The authors found analytically (by employing Darwin's expansion of the parabolic cylinder functions of large order and argument) that a surface mode localized at the zigzag edge remains dispersionless even in the presence of an electric field. Keith Slevin and Tomi Ohtsuki [article number 2300080] studied irrelevant corrections to scaling of the previously reported data for the Lyapunov exponents of the Chalker–Coddington model using both polynomial fitting and Gaussian process fitting. They implemented a new scaling Ansatz, proposed by Dresselhaus et al., to study the two-terminal conductance. The main conclusion of their research is that the factorization Ansatz, while giving acceptable fits for some ranges of data, is possibly not exact. Porous semiconductor compounds represent a class of materials under intense research focus over the last few years. Eduard V. Monaico, Elena I. Monaico, Veaceslav V. Ursaki, and Ion M. Tiginyanu [article number 2300039] studied the effect of anodization in binary semiconductor compounds having various bandgaps and crystallographic orientations. They presented morphologies and topologies with a focus on technological procedures applied for generating arrays of pores with a controlled design. They discussed the mechanism of pores growth under the photoresist masks and the connection between the mask's design and the architecture of the produced porous structure. Investigations of various physical properties used scanning electron microscopy, photoluminescence, cathodoluminescence spectroscopy, and contact angle measurements. Igor Yurkevich and Victor Kagalovsky [article number 2200485] studied a strongly interacting 1D system with many channels. When single-electron inter-channel backscattering processes become relevant, they freeze corresponding fields, whereas other fields remain free. It is natural then to use a new basis built on these gapped and free fields. A mathematical procedure to separate gapped and conducting channels is proposed. The authors solved exactly the problem for a two-channel system with inter-channel counter-clockwise backscattering as relevant perturbation for arbitrary intra- and inter-channel interactions. They found effective Luttinger parameter and velocity for the free field. The parameters of the free field are independent of the interactions between right- and left-moving electrons in the same channel and between electrons moving in the same direction in different channels. Finally, if the interchannel interactions are weak, the free field becomes noninteracting (effective Luttinger parameter is equal to one) independently of the intra-channel interactions’ strength. Igor Bogush and Vladimir M. Fomin [article number 2300064] studied superconductor Nb open nanotubes under a strong transport current in an applied magnetic field on the base of the time-dependent Ginzburg–Landau equation. The hysteresis effect in the current–voltage characteristics emerges due to the different regimes of order parameter dynamics. The upper and lower branches of the hysteresis loop are manifestations of the phase-slip and vortex regimes, correspondingly. The geometric characteristics of the hysteresis loop are found for nanotubes of radii varying from 190 to 440 nm as a function of the applied magnetic field. In nanotubes of radii of 240 nm and larger, the area of the hysteresis loop is a non-monotonous function of the applied magnetic field with a maximum in the range from 15 to 20 mT. Interestingly, normal conductivity crucially influences the hysteresis effect in superconductor open nanotubes. In particular, the hysteresis effect disappears under a high enough normal conductivity. The topology and geometry determine the phonon spectrum and thermal conductivity of nanoarchitectures. Igor Bogush [article number 2300037] reveals that the phonon spectra do not differ for rolled-up nanotubes and concentric multi-walled nanotubes when the nanotube radius is much larger than the lattice constant. In case if the interlayer contact of the rolled-up or concentric multi-walled nanotubes is weak, the thermal conductivity practically is not affected by the contact, and the conductivity of the one-layered flat membrane can adequately approximate it. In the case of weak contact, there exists an appreciable difference in the diffusive heat transfer between rolled-up and concentric multi-walled nanotubes of large radii. Thus, the weak interlayer contact can significantly influence the experimental measurements. Superconducting bridges exhibit a number of properties of a Josephson Junction, like the electromagnetic radiation occurring at overcritical currents and steps in the microwave-irradiated current–voltage (I–V) curves. These Josephson effects stem from the periodic motion of superconducting vortices in the narrowest region of the bridge. According to the Aslamazov and Larkin (AL) model, the I–V curve of a constriction exhibits a voltage kink each time the number of vortices in a 1D vortex chain increases by one. However, in the presence of fluctuations and defects, the repulsion between vortices stipulates formation of a 2D vortex jet, which goes beyond the 1D vortex chain model by AL. By milling one or two slits across a MoSi thin strip, Volodymyr M. Bevz, Barbora Budinska, Sebastian Lamb-Camarena, Stanislava O. Shpilinska, Clemens Schmid, Mikhail Yu. Mikhailov, Wolfgang Lang and Oleksandr V. Dobrovolskiy [article number 2200513] make vortices to move in a vortex–jet or a vortex–chain fashion, respectively. Unexpectedly, for the strip with a vortex jet, equidistant voltage kinks are observed at transport currents which are relatively far from the assumption of the AL model. The authors attribute this observation to fast relaxation processes in MoSi. Gian Paolo Papari and Vladimir M. Fomin [article number 2300038] analyzed the origin of the parabolic background of magnetoresistance oscillations experimentally detected in superconducting mesoscopic rings of finite width with input and output stubs as well as in patterned films. The transmission model that explained the oscillations of magnetoresistance is extended to address the parabolic background as a function of the magnetic field. Along with the interference mechanism activated by the ring as a doubly-connected structure, pinned superconducting vortices introduce a further interference-driven distribution of supercurrents, which affects the voltmeter-sensed quasiparticles. The onset of vortices in a mesoscopic ring allows for attributing the full magnetoresistance to the interference of the constituents of the order parameter induced by both the ring with its doubly-connected topology and the vortex array in it. The present Special Issue “Topological and geometrical effects in complex nanostructures” not only allows for the presentation of exciting new results and their intense discussions at the Mini-Colloquium in Manchester, but also opens opportunities for new collaborations and achievements in this fascinating and vigorously developing field of Condensed Matter Physics. We gratefully acknowledge the enthusiastic support of the present Special Issue by the Editor of Physica Status Solidi (Rapid Research Letters) Dr. Stefan Hildebrandt. Professor Dr. Vladimir M. Fomin is university professor in theoretical physics (State University of Moldova, since 1995) and scientific researcher at the Leibniz IFW Dresden (since 2009). He led scientific discovery of the phenomenon of the propagation of spatially-extended interface phonon polaritons in composite superlattices (ANS of Russia, 1999). He is honorary member of the AS of Moldova (2007). He is outstanding reviewer of APS (2023). His research interests are in nanophysics: topology- and geometry-induced properties of 3D superconductor micro-/nanoarchitectures, topological effects in quantum rings, topological states of light in optical microcavities of complex geometry, optical properties of QDs, thermoelectric properties of semiconductor nanostructures, spin-dependent phenomena in semiconductor nanoparticles, vibrational excitations and polaron effects in nanostructures and in TMDs, propulsion mechanisms of tubular micromotors, and application for cleaning polluted water. He has authored six monographs, including “Self-rolled micro- and nanoarchitectures” (2021) and “Physics of Quantum Rings” (2014 and 2018). Professor Victor Kagalovsky is a dean of the faculty of engineering and head of R&D at Shamoon College of Engineering in Be'er-Sheva, Israel. His main research interests are mesoscopic physics, transport properties, and metal-insulator transitions in low-dimensional systems. He studied quantum Hall effects in 2D electron gas (charge effect) and disordered superconductors (spin and thermal effects). His recent research examines Wigner crystals in 2D systems, the robustness of the edge states in topological insulators, phase transitions, and the emergence of superconductivity in 1D ystems. He served as an organizer of international conferences in Dresden, Trieste, and Daejeon. During the last 15 years, he was also a visiting professor at Max-Planck-Institut für Physik Komplexer Systeme in Dresden, at the Northeastern University in Boston, and at the Center for Theoretical Physics of Complex Systems, Institute of Basic Research, Daejeon, South Korea. Zigzag ; Physics ; Topology (electrical circuits) ; Geometry ; Theoretical physics ; Condensed matter physics ; Mathematics Advanced Physical and Chemical Molecular Interactions ; Crystallography and Radiation Phenomena ; Graphene research and applications