We consider quasiperiodic nonconservative perturbations of two-dimensional nonlinear Hamiltonian systems. We introduce the notion of a degenerate resonance and study the topology of a degenerate ...resonance zone with odd and even orders of degeneracy. A special attention is paid the oscillation synchronization while an invariant torus is passing through the resonance zone. We establish the existence of synchronization intervals with respect to a control parameter. The study is based on the analysis of a pendulum–type averaged system determining the dynamics in the resonance zone.
Abyssal channels are the key points controlling bottom circulation of the World Ocean. They provide meridional transport of the coldest Antarctic Bottom Water between deep-water basins influencing ...the meridional overturning circulation and the climate on a global scale. Here we show that the synoptic variability of deep-water flows including blocking abyssal currents between deep ocean basins is related to sea level anomalies observed over the channels. Our results demonstrate that processes at the ocean surface have a more significant connection with the bottom circulation than it was considered earlier. This study opens a discussion of the importance of mesoscale eddies and air-sea interactions on water exchange between abyssal basins, meridional heat transport in the ocean, and possible responses of the ocean to the observed sea level rise in a changing climate.
We study quasiperiodic nonconservative perturbations of two-dimensional Hamiltonian systems with nonmonotone rotation. We study the behavior of solutions in neighborhoods of resonance energy levels ...close to degenerate ones. We find conditions for the existence of resonance quasiperiodic solutions (m-dimensional invariant tori in the extended phase space) and study bifurcations in resonance zones. The results are illustrated by an example of asymmetric Duffing equation for which we also solve the problem of constructing solutions of unperturbed equations.
At very small twist angles of ∼0.1°, bilayer graphene exhibits a strain-accompanied lattice reconstruction that results in submicron-size triangular domains with the standard, Bernal stacking. If the ...interlayer bias is applied to open an energy gap inside the domain regions making them insulating, such marginally twisted bilayer graphene is expected to remain conductive due to a triangular network of chiral one-dimensional states hosted by domain boundaries. Here we study electron transport through this helical network and report giant Aharonov-Bohm oscillations that reach in amplitude up to 50% of resistivity and persist to temperatures above 100 K. At liquid helium temperatures, the network exhibits another kind of oscillations that appear as a function of carrier density and are accompanied by a sign-changing Hall effect. The latter are attributed to consecutive population of the narrow minibands formed by the network of one-dimensional states inside the gap.
This book is devoted to the structure of the Mandelbrot set — a remarkable and important feature of modern theoretical physics, related to chaos and fractals and simultaneously to analytical ...functions, Riemann surfaces, phase transitions and string theory. The Mandelbrot set is one of the bridges connecting the world of chaos and order.
Cyclotron motion of charge carriers in metals and semiconductors leads to Landau quantization and magneto-oscillatory behavior in their properties. Cryogenic temperatures are usually required to ...observe these oscillations. We show that graphene superlattices support a different type of quantum oscillation that does not rely on Landau quantization. The oscillations are extremely robust and persist well above room temperature in magnetic fields of only a few tesla. We attribute this phenomenon to repetitive changes in the electronic structure of superlattices such that charge carriers experience effectively no magnetic field at simple fractions of the flux quantum per superlattice unit cell. Our work hints at unexplored physics in Hofstadter butterfly systems at high temperatures.
Giant Nonlocality Near the Dirac Point in Graphene Abanin, D. A.; Morozov, S. V.; Ponomarenko, L. A. ...
Science (American Association for the Advancement of Science),
04/2011, Letnik:
332, Številka:
6027
Journal Article
Recenzirano
Odprti dostop
Transport measurements have been a powerful tool for discovering electronic phenomena in graphene. We report nonlocal measurements performed in the Hall bar geometry with voltage probes far away from ...the classical path of charge flow. We observed a large nonlocal response near the Dirac point in fields as low as 0.1 tesla, which persisted up to room temperature. The nonlocality is consistent with the long-range flavor currents induced by the lifting of spin/valley degeneracy. The effect is expected to contribute strongly to all magnetotransport phenomena near the neutrality point.
Small perturbative fields in a synchrotron influence both the spin and orbital motion of a stored beam. Their effect on the beam polarization consists of two contributions, a direct kick and an ...effect of the ring lattice due to orbit perturbation. Spin response function is an analytic technique to account for both contributions. We develop such a technique for the spin-transparent synchrotrons where the design spin motion is degenerate. Several perspective applications are illustrated or discussed. In particular, we consider the questions of the influence of lattice imperfections on the spin dynamics and spin manipulation during an experiment. The presented results are of a direct relevance to NICA (JINR), RHIC (BNL), EIC (BNL) and other existing and future colliders when they arranged with polarization control in the spin-transparent mode.
•Sensitized Mn2+ luminescence is studied in lithium tetraborate.•Existence of complex luminescence centres is proposed.•Slow or ultrafast Mn2+ luminescence decays occur depending on the excitation ...energy.•Mechanisms for excitation transfer and luminescence decay acceleration are proposed.
Sub-nanosecond luminescence of Mn2+ in Mn-, Sn/Mn-, and Cu/Mn-doped Li2B4O7 ceramics is observed under laser excitation. Picosecond pulsed laser radiation (350–370 nm) generates the frequency-doubled radiation directly in a single microcrystal selected in a ceramic sample, with this secondary radiation falling within the impurity-induced VUV excitation bands of doped Li2B4O7. These excitation bands are attributed to the creation of an impurity-bound intra-anionic exciton in MeiO4–BO3–MnLi complex centres (Mei = Mn, Sn, or Cu). The exciton, in turn, interacts with a nearby Mn2+ ion due to mixing of the Mn2+ excited states with the excitonic states. Exciton annihilation involves Mn2+ energy levels as transient states and causes a sub-nanosecond radiative transition which is accelerated, being accompanied by rearrangement of the surrounding atoms. Excitation within the lower-energy bands is related to the other part of the complex luminescence centre, this is metal-to-ligand intra-anionic charge transfer, which makes an electron accessible to MnLi, while the hole is transferred only during relaxation of the excited structure. Mn2+ radiative transitions are not forced in the latter case, and slow Mn2+ luminescence decay is observed.
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