arXiv subjects

Igor Neri

Publications and source records attributed to Igor Neri.

7 recordsLinked to original sources

arXiv2017

Operating Gravitational Wave Detectors far from equilibrium

Tiny vibrations of mechanical structures are the main limiting cause in a number of high sensitivity measurement apparatus, chief among them the most sensitive displacement apparatus on earth: gravitational wave interferometers. Such devices are usually operated at equilibrium and small fluctuations are perceived as noise that sets a lower limit to the detection capabilities. An example is the so-called thermal noise, ubiquitous and unavoidable. In this letter we present an approach aimed at operating the interferometer out of equilibrium. We show that selective cooling of single modes of the mechanical structure is able to positively impact the measurement sensitivity, in selected frequency ranges. Experiments conducted on thin silica membranes show promising results for the implementation of such technique in next generation gravitational wave detectors.

physics.ins-det↗

arXiv2017

Cost of remembering a bit of information

In 1961, Rolf Landauer pointed out that resetting a binary memory requires a minimum energy of $k_BT \ln(2)$. However, once written, any memory is doomed to loose its content if no action is taken. To avoid memory losses, a refresh procedure is periodically performed. In this paper we present a theoretical model and an experiment on a micro-electro-mechanical system to evaluate the minimum energy required to preserve one bit of information over time. Two main conclusions are drawn: i) in principle the energetic cost to preserve information for a fixed time duration with a given error probability can be arbitrarily reduced if the refresh procedure is performed often enough; ii) the Heisenberg uncertainty principle sets an upper bound on the memory lifetime.

cond-mat.stat-mech↗

arXiv2016

Electronic transport modulation on few-layers suspended MoS$_2$ under strain

The production of new sensors, transducers and electronic components can benefit from the possibility to alter the electronic transport of metal-semicondutor-metal (MSM) devices. 2D materials are extremely appealing for those new technologies. This can determined by several phenomena as piezoelectric effect, piezoresistive effect and modulation of Schottky barrier. In particular, MoS$_2$, among other Transition Metal Dichalcogenides (TMDs), is predicted to show a transition from semiconductor to metal under strain. In this article we present measurements on the modulation of electronic transport on few layer MoS$_2$ suspended ribbons under uniaxial tensile strain. Experimentally observed changes in the two terminal IV curves can be explained in terms of band gap closing in the semiconductor. A maximum gauge factor of 240 is achieved for a 3-layer ribbon. We also report on the fabrication process that allows to apply high strains to suspended MoS$_2$ ribbons, paving the way to future studies on the effect of strain in 2D materials.

cond-mat.mtrl-sci↗

arXiv2016

Heat production and error probability relation in Landauer reset at effective temperature

The erasure of a classical bit of information is a dissipative process. The minimum heat produced during this operation has been theorized by Rolf Landauer in 1961 to be equal to $k_B T \ln 2$ and takes the name of Landauer limit, Landauer reset or Landauer principle. Despite its fundamental importance, the Landauer limit remained untested experimentally for more than fifty years until recently when it has been tested using colloidal particles and magnetic dots. Experimental measurements on different devices, like micro-mechanical systems or nano-electronic devices are still missing. Here we show the results obtained in performing the Landauer reset operation in a micro-mechanical system, operated at an effective temperature. The measured heat exchange is in accordance with the theory reaching values close to the expected limit. The data obtained for the heat production is then correlated to the probability of error in accomplishing the reset operation.

cond-mat.mes-hall↗

arXiv2016

Micro-electromechanical memory bit based on magnetic repulsion

A bistable micro-mechanical system based on magnetic repulsion is presented exploring its applicability as memory unit where the state of the bit is encoded in the rest position of a deflected cantilever. The non-linearity induced on the cantilever can be tuned through the magnetic interaction intensity between the cantilever magnet and the counter magnet in terms of geometrical parameters. A simple model provides a sound prediction of the behavior of the system. Finally we measured the energy required to store a bit of information on the system that, for the considered protocols, is bounded by the energy barrier separating the two stable states.

cond-mat.mes-hall↗

arXiv2016

Band gap engineering of MoS$_2$ upon compression

Molybdenum disulfide (MoS$_2$) is a promising candidate for 2D nanoelectronic devices, that shows a direct band-gap for monolayer structure. In this work we study the electronic structure of MoS$_2$ upon both compressive and tensile strains with first-principles density-functional calculations for different number of layers. The results show that the band-gap can be engineered for experimentally attainable strains (i.e. $\pm 0.15$). However compressive strain can result in bucking that can prevent the use of large compressive strain. We then studied the stability of the compression, calculating the critical strain that results in the on-set of buckling for free-standing nanoribbons of different lengths. The results demonstrate that short structures, or few-layer MoS$_2$, show semi-conductor to metal transition upon compressive strain without bucking.

cond-mat.mtrl-sci↗

arXiv2015

Sub $k_B T$ micro-electromechanical irreversible logic gate

In modern computers, computation is performed by assembling together sets of logic gates. Popular gates like AND, OR, XOR, processing two logic inputs and yielding one logic output, are often addressed as irreversible logic gates where the sole knowledge of the output logic value, is not sufficient to infer the logic value of the two inputs. Such gates are usually believed to be bounded to dissipate a finite minimum amount of energy determined by the input-output information difference. Here we show that this is not necessarily the case, by presenting an experiment where a OR logic gate, realized with a micro electromechanical cantilever, is operated with energy well below the expected limit, provided the operation is slow enough and frictional phenomena are properly addressed.

cond-mat.mes-hall↗