Nanotechnology Now

Our NanoNews Digest Sponsors



Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > Scientists observe quantum superconductor-metal transition and superconducting glass: A team including MIPT physicist observed quantum superconductor-metal transition and superconducting glass

Abstract:
The article "Collapse of superconductivity in a hybrid tin-grapheme Josephson junction array'" (authors: Zheng Han, Adrien Allain, Hadi Arjmandi-Tash,Konstantin Tikhonov, Mikhail Feigelman, Benjamin Sacépé,Vincent Bouchiat, published in Nature Physics on March 30, 2014, DOI:10.1038/NPHYS2929) presents the results of the first experimental study of the graphene-based quantum phase transition of the "superconductor-to-metal" type, i.e. transformation of the system's ground state from superconducting to metallic, upon changing the electron concentration in graphene sheet.

Scientists observe quantum superconductor-metal transition and superconducting glass: A team including MIPT physicist observed quantum superconductor-metal transition and superconducting glass

Moscow, Russia | Posted on April 16th, 2014

The system is a regular array of tin nanodisks (the radius of each disk is 200 nm) situated on a graphene substrate. Tin becomes a superconductor at temperatures lower than T0 = 3.5 degrees Kelvin. Tin nanodiscs electrically contact with each other due to electronic conductivity through graphene. At temperatures significantly below T0 the state of the nanodisk can be characterized by a single variable - "phase," defined in the period from 0 to 2π. Due to the transfer of Cooper pairs of electrons between nanodiscs the so-called Josephson junctions are formed, which seek to establish a coherent superconducting state with uniform nanodisk phases across the entire lattice.

Graphene allows to gradually change the density of conduction electrons in it by changing the voltage on the electrostatic gate, and thus the strength of Josephson junctions between tin nanodiscs. Phase correlations among nanodiscs are destroyed by thermal fluctuations at temperatures above the critical temperature Tc. At high density of conduction electrons in graphene the measured value Tc (around 0.5-0.7 K) is in good agreement with the previously developed theory, published in the article by Feigel'man, M.; Skvortsov, M. & Tikhonov, K. Theory of proximity-induced superconductivity in graphene, Solid State Communications, *149*, 1101 - 1105 (2009).

Upon lowering the electron density of grapheme the energies of Josephson junctions weaken due to increase in the resistance of graphene, and the temperature of transition into coherent state drops sharply to below the minimum temperature of the experiment (60 mK). In other words, the spatial phase coherence between different individual nanodisks is destroyed solely by quantum (independent of temperature) phase fluctuations. As a result, superconductor-to-metal quantum phase transition takes place.

First approach to the theory of such a phase transition have previously been developed in the paper Feigel'man, M.; Larkin A. & Skvortsov, M. "Quantum superconductor-metal transition in a proximity array," Physical Review Letters *86* 1869, (2001).

In the domain of lowest measurable temperatures the resistance of the studied array turns out to be nearly temperature-independent, and, at the same time, it is an exponentially sharp function of voltage on the electric back-gate; this observation is yet to be explained as no complete theory is capable of describing it at present.

In addition to the above-mentioned superconductor-to-metal transition, the authors discovered the so-called "superconducting glass" state, which is created as a result of disorder and frustration in the Josephson junctions, but nevertheless corresponds to some of the minima of the total energy of the Josephson junctions array. Here, the controlling parameter is the strength of external magnetic field. Competition of periodic dependency on the magnitude of magnetic flux through the elementary cell of the nanodisk lattice and random dependency on the same parameter (due to mesoscopic fluctuations) leads to a phase diagram of the "re-entrant" type. Namely, the magnitude of the maximum superconducting current that flows through the entire lattice depends non-monotonically upon an external magnetic field; first it decreases (all the way down to zero), and then reappears with the increase of the magnetic field in a certain range of its values.

###

####

For more information, please click here

Contacts:
Alexandra O. Borissova

7-495-408-6445

Copyright © Moscow Institute of Physics and Technology

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

New synthesis method may shape future of nanostructures, clean energy: Findings advance efficient solar spliting of water into hydrogen fuel September 2nd, 2014

Accounting for Biological Aggregation in Heating and Imaging of Magnetic Nanoparticles September 2nd, 2014

Engineers develop new sensor to detect tiny individual nanoparticles September 2nd, 2014

Future solar panels September 2nd, 2014

Graphene

Competition for Graphene: Berkeley Lab Researchers Demonstrate Ultrafast Charge Transfer in New Family of 2D Semiconductors August 26th, 2014

Graphene Structure Studied in Iran by Novel Method August 25th, 2014

Graphene may be key to leap in supercapacitor performance August 20th, 2014

Ultrasonic Waves Applied in Production of Graphene Nanosheets August 20th, 2014

Superconductivity

Study finds physical link to strange electronic behavior: Neutron measurements offer new clues about iron-based superconductor July 31st, 2014

UCF Nanotech Spinout Developing Revolutionary Battery Technology: Power the Next Generation of Electronics with Carbon July 23rd, 2014

Flashes of light on the superconductor: Using light to modulate the properties of a copper-based superconductor July 15th, 2014

Iranian researchers Produce High-Temperature Superconductive Nanorods July 7th, 2014

Discoveries

Secure Computing for the ‘Everyman': Quantum computing goes to market in tech transfer agreement with Allied Minds September 2nd, 2014

Cool Calculations for Cold Atoms: New theory of universal three-body encounters September 2nd, 2014

UO-Berkeley Lab unveil new nano-sized synthetic scaffolding technique: Oil-and-water approach from Richmond's UO lab to spark new line of versatile peptoid nanosheets September 2nd, 2014

Future solar panels September 2nd, 2014

Announcements

New synthesis method may shape future of nanostructures, clean energy: Findings advance efficient solar spliting of water into hydrogen fuel September 2nd, 2014

Accounting for Biological Aggregation in Heating and Imaging of Magnetic Nanoparticles September 2nd, 2014

Engineers develop new sensor to detect tiny individual nanoparticles September 2nd, 2014

Future solar panels September 2nd, 2014

Interviews/Book Reviews/Essays/Reports/Podcasts/Journals

UO-Berkeley Lab unveil new nano-sized synthetic scaffolding technique: Oil-and-water approach from Richmond's UO lab to spark new line of versatile peptoid nanosheets September 2nd, 2014

New synthesis method may shape future of nanostructures, clean energy: Findings advance efficient solar spliting of water into hydrogen fuel September 2nd, 2014

Engineers develop new sensor to detect tiny individual nanoparticles September 2nd, 2014

Future solar panels September 2nd, 2014

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More














ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







© Copyright 1999-2014 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE