178,280 research outputs found
Thouless pumping and topology
No full textPhysicists and engineers from all around the world are constantly thinking of ways to improve the performance of conventional electronic devices by reducing the dissipated energy and to this aim recently is working its way employing quantum technologies. In a conductor a direct current is usually associated with a dissipative flow of electrons in response to an applied bias voltage. In quantum systems, however, a dissipationless transport can be induced via adiabatic cyclic variation of the system parameters in the absence of any external bias. An example is the quantum pump, or Thouless pump, the quantum version of the famous Archimede’s screw in which water from a low-level is pushed up the tube by the slow and periodic rotation of the helicoid. The quantum device is obtained slowly time periodic potential. Interestingly, the charge pumped after a period is quantized and is connected to a bulk property of the system, the so called topological invariant, i.e. a property of a geometric shape that does not change when the shape is stretched or distorted and thus is robust to external perturbations.
The exciting developments in the exploitation of quantum pumps have been reported in an article of the prestigious journal Nature Reviews Physics involving the Department of Physics at University of Salerno, where a research on quantum devices is coordinated by Prof. Roberta Citro, and the Quantum Optics group at Ludwig Maximilian University of Munich, led by Prof. Monika Aidelsburger. The article describes in details various quantum pumps, arguing how they produce a lot less heat than conventional electric currents generators, making them promising candidates for future electronic devices with significantly reduced power consumption.
Quantum pumping has received much attention in mesoscopic electronic systems, mainly owing to its potential of reducing the dissipation of energy as wasteful heat, for defining a better current standard for metrological purpose or even being used for quantum computing. Recent experimental realizations of Thouless pumps have been observed in photonics, magneto-mechanical and electro-mechanical systems and other examples cover the fields of spintronics with implications in the efficiency of data storage and transfer
Effect of magnetic field induced spin chiral-interaction on quasi-one dimensional spin systems
No full textProgresses on topological phenomena, time-driven phase transitions, and unconventional superconductivity
No full textIn this perspective we discuss three emerging fields of condensed matter physics which in recent years have attracted considerable attention. In particular, we consider the recent challenging topics on time-dependent phase transitions, topological phenomena, and unconventional superconductivity, with the aim to foster the community towards new applications and technological advancements. As for the time-dependent phase transitions, in recent years the experiments have shown light-induced phase transitions and new fields of application are emerging, including material design. Regarding topological materials, new challenges have arisen to detect the Majorana origin of quantized conductance in superconducting hybrid structures, as well as the effect of interaction on edge channels. Finally, concerning superconductivity, non-conventional pairing and correlation effects dominate the physics of a vast class of two-dimensional materials and novel devices were recently conceived. This work offers a comprehensive overview on these topics for promoting new ideas in these fertile fields of research
Long-term analysis of stochastic θ-methods for damped stochastic oscillators
No full textWe analyze long-term properties of stochastic θ-methods for damped linear stochastic oscillators. The presented a-priori analysis of the error in the correlation matrix allows to infer the long-time behaviour of stochastic θ-methods and their capability to reproduce the same long-term features of the continuous dynamics. The theoretical analysis is also supported by a selection of numerical experiments
Theory of a peristaltic pump for fermionic quantum fluids
No full textMotivated by the recent developments in fermionic cold atoms and in nanostructured systems, we propose the model of a peristaltic quantum pump. Differently from the Thouless paradigm, a peristaltic pump is a quantum device that generates a particle flux as the effect of a sliding finite-size microlattice. A one-dimensional tight-binding Hamiltonian model of this quantum machine is formulated and analyzed within a lattice Green's function formalism on the Keldysh contour. The pump observables, as, e.g., the pumped particles per cycle, are studied as a function of the pumping frequency, the width of the pumping potential, the particles mean free path, and system temperature. The proposed analysis applies to arbitrary peristaltic potentials acting on fermionic quantum fluids confined to one dimension. These confinement conditions can be realized in nanostructured systems or, in a more controllable way, in cold atoms experiments. In view of the validation of the theoretical results, we describe the outcomes of the model considering a fermionic cold atoms system as a paradigmatic example
Non-Hermitian topological phases in an extended Kitaev model
No full textIn this work we address the study of topological phase protection of open quantum systems. Using the self-energy formalism, we investigate the paradigmatic case of an extended Kitaev model. The results show how the topological order can be affected by coupling the system to two external leads, giving rise to Non-Hermitian topological phases. Our results could be useful in spectroscopic measurements made on nanowire-based mesoscopic devices
Nearly conservative multivalue methods with extended bounded parasitism
No full textThe paper is focused on the analysis of parasitism for multivalue numerical methods intended as geometric numerical integrators for Hamiltonian problems. In particular, the main topic is the design of multivalue numerical methods whose parasitic components remain bounded over certain time intervals, opening the path to the development of nearly conservative multivalue methods able to guarantee a control of parasitism in the long time. The analysis of parasitism as well as the development of the corresponding methods is the core of the treatise. The effectiveness of the approach is also confirmed on selected Hamiltonian problems
Review of \u3cem\u3eProtecting Participants and Facilitating Social and Behavioral Sciences Research.\u3c/em\u3e Constance F Citro, Daniel R. Iglen and Cora B. Marrett (Eds.).
No full textBook book note for Constance F. Citro, Daniel R. Iglen and Cora B. Marrett (Eds.), Protecting Participants and Facilitating Social and Behavioral Sciences Research. Washington, DC: National Academies Press, 2003. $39.00 papercover
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