More information: Ofir Shein Lumbroso et al. Electronic noise due to temperature differences in atomic-scale junctions, Nature (2018). DOI: 10.1038/s41586-018-0592-2 Elke Scheer et al. Unexpected noise from hot electrons, Nature (2018). DOI: 10.1038/d41586-018-06932-x A. Hamo et al. Electron attraction mediated by Coulomb repulsion, Nature (2016). DOI: 10.1038/nature18639 A single-quantum mechanical transport channel constituted the resulting junctions wherein electrons could be transmitted from one electrode to the other. The probability of electron transfer could be adjusted by varying the openness of the channel. An ideal test bed setup was thus provided to explore the properties of noise contribution so far overlooked. When a temperature difference was applied between the two electrodes, the authors observed a strong increase in electronic noise compared with electrodes at the same temperature. The new noise, termed ‘delta-T noise,’ scaled with the square of the temperature difference, exhibiting similar dependence on electrical conductance as shot noise. Citation: Electronic noise due to temperature difference in atomic-scale junctions (2018, October 30) retrieved 18 August 2019 from https://phys.org/news/2018-10-electronic-noise-due-temperature-difference.html Experimental setup and noise contributions. a) Schematic of the break junction setup and the gold-hydrogen (Au/H2) junction. b) Illustration of standard shot noise, thermal noise and delta-T defined above, generated in atomic-scale junctions, e is electron charge. Credit: Nature, doi: 10.1038/s41586-018-0592-2. © 2018 Science X Network More than a century ago, in 1918, German Physicist Walter Schottky published a paper describing causes and manifestations of noise in electrical measurements. In the publication, Schottky showed that an electric current produced by an applied voltage was noisy, even at absolute zero temperature, when all random heat-induced motion had stopped. The noise was a direct consequence of quantized electric charge that arrived in discrete units. The noise was termed ‘shot noise,’ as it resulted from the granularity of the charge flow. In systems that are in thermal equilibrium, noise with distinctly different properties from shot noise came into play at non-zero temperatures known as Johnson-Nyquist noise. Shot noise is now a key tool to characterize nanoscale electrical conductors, since it contains information on quantum-transport properties that cannot be revealed via mere electric-current measurements. In the study, the authors studied junctions composed of single atoms or molecules suspended between a pair of gold electrodes. The electrodes were fabricated by breaking a thin gold wire into two parts and bringing them gently back in to contact. In this process, hydrogen molecules were evaporated onto the device, known as a mechanically controllable break junction, to capture individual atoms or molecules between the electrode tips and establish an electrical contact. A mysterious insulating phenomenon in a superconductor Three types of electronic noise. Experimental setup where single atoms or molecules are suspended between the tips of two electrodes. a) At a non-zero temperature (red) electrons flow between the two electrodes (arrows). The associated electrical signal contains thermal noise, which varies linearly with electrical conductance (shown in units of quantum conductance). b) If a voltage is applied to the device, electrons flow from one electrode to another and can be backscattered from the atom or molecule. The resulting signal contains ‘shot’ noise that is present even when the device is at absolute zero temperature (blue). Shot noise has a characteristic (non-monotonic) dependence on conductance. c) If a temperature gradient is applied to the device (indicated from temperatures rising through blue to purple and red) electrons flow from both electrodes and can be backscattered. The study showed that the resulting electrical signal contained a previously unreported type of noise, named delta-noise. This noise depends on conductance similar to shot noise. Credit: Nature News and Views, doi: https://www.nature.com/articles/d41586-018-06932-x Journal information: Nature This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Explore further Noise is a fundamental feature of any electrical measurement that calculates random and correlated signal fluctuations. Although noise is typically undesirable, noise can be used to probe quantum effects and thermodynamic quantities. Writing in Nature, Shein Lumbroso and co-workers now report a new type of electronic noise discovered to be distinct from all other previous observations. Understanding such noise can be essential to design efficient nanoscale electronics. The findings of the study were explained via the quantum theory of charge transport known as Landauer theory, developed in the past few decades. The theory included both shot noise and thermal noise for intensive testing at the atomic and molecular scale. The theory accurately described many experimental observations when working entirely in thermal equilibrium or when applying small voltages. On closer inspection of the theory, the authors observed that inclusion of a noise component only occurred when a temperature difference was solely applied across a junction as experimentally observed with delta-T noise. In the absence of an applied voltage, an electric current can arise due to a temperature difference via a phenomenon termed the Seebeck effect. According to the study, the delta-T noise arose from the discreteness of the charge carriers mediating the heat transport.Although the Landauer theory is widely used, surprisingly, delta-T noise was not previously observed. The present work therefore conveyed a key message that careful experimental design and rigorous analysis are required to study the details of quantum transport. In practice, quantum-transport experiments that weren’t entirely in thermal equilibrium could show strongly enhanced noise, which could be mistaken for noise arising from interactions between charge carriers or due to subtle effects. Unexpectedly high noise in electric-current measurements could be due to unintentional temperature gradients in experimental setups. In practice, the authors’ work can potentially be used to detect undesirable hot spots in electrical circuits. Future experimental focus will explore the relationship between delta-T noise and shot noise, with a nonlinear dependence on applied voltage. This phenomenon was recently observed in high-voltage experiments at atomic junctions. In combination with thermal noise, delta-T noise can be used as a probe for temperature differences in nanoscale systems. Delta-T noise is a versatile probe compared to physical sensors, not limited to a particular setup range, and that can be applied to conductors of variable sizes, including those at the atomic scale. The versatility allows delta-T noise to become an attractive tool for heat management, which includes thermoelectricity, heat pumping and heat dissipation, important for energy saving and sustainable energy production. Since temperature gradients are often unintentionally produced in electronic circuits, to prevent performance-limiting effects of delta-T noise, the temperature gradients should be minimized. The sensitivity of delta-T noise on the properties and interactions of charge carriers could become a valuable tool in quantum-transport.
Legends of India Life Achievement Awards are conferred upon living legends who have contributed in taking our art forms to a different platform among the masses in India and abroad. One of India’s most prestigious awards shall be presented on the occasion of 15th Annual Legends of India Sangeet Mahotsav.The Sangeet Mahotsav is dedicated to Swami Vivekananda on the occasion of his 150thBirth anniversary. The music of Swami Vivekananda ‘Dhrupad’ shall be the central theme of the festival. Swami Shantatmananda, Secretary, Ramkrishna Mission, will grace the occasion. Also Read – ‘Playing Jojo was emotionally exhausting’Vivekananda was an exponent of Dhrupad and he also played the tabla, tanpura, khol and pakhawaj. Dhrupad, a genre of Hindustani classical music is said to be the oldest in use in the music tradition. To be held at the Siri Fort Auditorium December 26-27 the live performances of Uday Bhawalkar (Vocal) Bhai Baldeep Singh (Vocal), Gundecha Brothers in jugalbandi with Igino Brunori and Virginia Nicoli (Saxophone and Flute), Ustad Bahauddin Dagar (Rudra Veena) besides a jugalbandi of flute by Ronu Majumdar and Rajan Sajan Mishra (Vocal). Also Read – Leslie doing new comedy special with NetflixThis year, the award for music shall be conferred upon the internationally renowned Hindustani classical vocalist, Prabha Atre. The award for theatre shall be conferred upon Ebrahim Alkazi is god’s gift to theatre, synonymous with the stage and all its forms. As the director (1962–77) of the National School of Drama, Alkazi catalyzed its emergence as India’s premier theatre training institute. The award for fine arts shall be conferred upon Himmat Shah who is one of India’s renowned sculptors of terracotta and bronze, exploring materiality as well as texture. The recipients ofthe award are chosen independently by a selection committee comprising of artists, critics and eminent people associated with the arts.
Kolkata: A youth identified as Suman Ghosh (24) was allegedly murdered by his neighbour Shukla Ghosh over a suspected illicit relationship with her at Nokari Ghosh Para in Ranaghat, Nadia.Locals later ransacked the accused’s house. According to them, Shukla used to live at a stone throwing distance from Suman’s house. Her husband lives outside of Bengal due to his profession. Locals alleged that during her husband’s absence Shukla used to hang out with several youths of the area. She had several illicit relationships with many youths. A few months ago a person who was in a relationship with Shukla got involved in a heated altercation with her over some problem. In distress, Shukla called Suman for help and since then Suman came close to her. Also Read – Rain batters Kolkata, cripples normal lifeAs both of them moved forward with their relationship, Suman discovered that Shukla has relations with other youths as well. During the Puja days, Suman protested against Shukla having multiple relationships. Over this both of them fought continuously. On Friday evening, Shukla called Suman to her house and together consumed alcohol. In the night, Suman felt sick after he returned his home. He was immediately rushed to Ranaghat Sub-Divisional Hospital and later referred to Jawaharlal Nehru Memorial Hospital at Kalyani where he was admitted. Suman died there on Saturday. Hearing the news, Shukla fled the area along with her daughter. On Sunday, Suman’s family members lodged a complaint. They alleged that Shukla poisoned Suman to death.
Kolkata: The Kolkata Port Trust (KoPT) has engaged L&T Consultancy to prepare a master plan for expanding its capacity to 90 million tonnes per annum in a period of four to five years. The move is set to cater to the demand trend of cargo that is expected to go up manifold in five to ten years from now.”Currently the capacity of KoPT is 62 million tonnes. However, with the demand trend and indications from the port users, we have engaged L&T Consultancy for a master plan to ramp up the cargo handling capacity to 90 million tonnes in 4-5 years. We have to be ready to cater to this additional cargo, as otherwise they will shift to other neighbouring ports,” KoPT chairman Vinit Kumar said on the sidelines of a roadshow in the city for the proposed Maritime Conclave 2019. Also Read – Speeding Jaguar crashes into Mercedes car in Kolkata, 2 pedestrians killedAccording to Kumar, KoPT has plans to increase Haldia’s capacity to 65 million tonnes from the existing 45 million tonnes and Kolkata Dock’s capacity to 25 million tonnes from the current capacity of 17-18 million tonnes. KoPT has already undertaken capacity expansion by having liquid outer terminals I and II in Haldia. Kumar’s plan of ramping up the capacity assumes significance with Steel Authority of India (SAIL) Executive Director L N Mallik speaking of their plan to increase production. Mallik had asked the ports to take measures for ensuring enhanced infrastructure to handle higher quantities of raw materials and finished goods. Two other leading steel companies are also taking measures to augment production. Also Read – Bose & Gandhi: More similar than apart, says Sugata Bose”Both Kolkata and Haldia have a good connectivity of road and rail network. So if we can achieve our target then we have bright days ahead,” a senior KoPT official said. According to Kumar, KoPT will soon float a tender for dredging the Kolkata Dock Complex for a period of 4 years, with an expenditure of Rs 88 crore. The dredging at Haldia Dock Complex has already begun. This will increase the draft of the river, encouraging big vessels to handle cargo through KoPT. Shipping ministry director (ports) Arvind Chaudhary said investment interests to the tune of USD 20 billion could be expected from the proposed Maritime Conclave, to be held in Bhubaneswar on February 14-15.