Skip to main content

TIFR discovery challenges theory of superconductivity(thehindu)


A team of researchers has discovered semi-conductivity in bismuth at around -273 C°


Researchers at the Tata Institute of Fundamental Research (TIFR), Mumbai, have made a landmark discovery that challenges the conventional understanding of superconductivity.

A team, lead by Dr. S. Ramakrishnan of the Department of Condensed Matter Physics and Material Sciences at TIFR, has discovered bismuth semi-metal in bulk form becoming a superconductor when the temperature is lowered to 530 microKelvin (about -273 degree C), which is three orders of magnitude higher than the theoretical prediction. The results were published in the journal Science .

“The Bardeen-Cooper-Schrieffer (BCS) theory [which explains superconductivity in most low Tc superconductors] cannot explain the superconductivity seen in bismuth,” said Dr. Ramakrishnan, the corresponding author of the paper. “The discovery demands a new theory and a new mechanism to understand superconductivity in bismuth. This discovery provides an alternative path for discovering new superconducting materials which are very different from the conventional superconductors.”



Superconductors are materials that conduct electricity with no resistance whatsoever. To become superconductors, the element should have mobile electrons, and these electrons should come together to form pairs, known as Cooper pairs. Unlike other elements in the periodic table, bismuth has unusual phenomenon — while metallic superconductors have one mobile electron per atom, bismuth has only one mobile electron per 100,000 atoms. Since carrier density is so small, people did not believe that bismuth will superconduct.

Also, bismuth’s electronic energy (Fermi energy) is comparable to the lattice (phonon) energy. “So the conventional BCS theory and its extensions which assume that Fermi energy is two to three orders of magnitude higher than phonon energy is not valid in bismuth. We know that if we prove superconductivity in bismuth, it will be from a different mechanism,” Dr. Ramakrishnan said.

“Superconductivity in bismuth is puzzling. Even at 10 milliKelvin, people did not find superconductivity in bismuth. So they gave up nearly 20 years back,” said Om Prakash Shukla from TIFR and the first author of the paper.
Labels:

Comments

Post a Comment

Popular posts from this blog

NGT terminates chairmen of pollution control boards in 10 states (downtoearth,)

Cracking the whip on 10 State Pollution Control Boards (SPCBs) for ad-hoc appointments, the National Green Tribunal has ordered the termination of Chairpersons of these regulatory authorities. The concerned states are Himachal Pradesh, Sikkim, Tamil Nadu, Uttarakhand, Kerala, Rajasthan, Telangana, Haryana, Maharashtra and Manipur. The order was given last week by the principal bench of the NGT, chaired by Justice Swatanter Kumar. The recent order of June 8, 2017, comes as a follow-up to an NGT judgment given in August 2016. In that judgment, the NGT had issued directions on appointments of Chairmen and Member Secretaries of the SPCBs, emphasising on crucial roles they have in pollution control and abatement. It then specified required qualifications as well as tenure of the authorities. States were required to act on the orders within three months and frame Rules for appointment [See Box: Highlights of the NGT judgment of 2016 on criteria for SPCB chairperson appointment]. Having
Post a Comment
Click Here To Read more »

High dose of Vitamin C and B3 can kill colon cancer cells: study (downtoearth)

In a first, a team of researchers has found that high doses of Vitamin C and niacin or Vitamin B3 can kill cancer stem cells. A study published in Cell Biology International showed the opposing effects of low and high dose of vitamin C and vitamin B3 on colon cancer stem cells. Led by Bipasha Bose and Sudheer Shenoy, the team found that while low doses (5-25 micromolar) of Vitamin C and B3 proliferate colon cancer stem cells, high doses (100 to 1,000 micromolar) killed cancer stem cells. Such high doses of vitamins can only be achieved through intravenous injections in colon cancer patients. The third leading cause of cancer deaths worldwide, colon cancer can be prevented by an intake of dietary fibre and lifestyle changes. While the next step of the researchers is to delineate the mechanisms involved in such opposing effects, they also hope to establish a therapeutic dose of Vitamin C and B3 for colon cancer stem cell therapy. “If the therapeutic dose gets validated under in vivo
1 comment
Click Here To Read more »

SC asks Centre to strike a balance on Rohingya issue (.hindu)

Supreme Court orally indicates that the government should not deport Rohingya “now” as the Centre prevails over it to not record any such views in its formal order, citing “international ramifications”. The Supreme Court on Friday came close to ordering the government not to deport the Rohingya. It finally settled on merely observing that a balance should be struck between humanitarian concern for the community and the country's national security and economic interests. The court was hearing a bunch of petitions, one filed by persons within the Rohingya community, against a proposed move to deport over 40,000 Rohingya refugees. A three-judge Bench, led by Chief Justice of India Dipak Misra, began by orally indicating that the government should not deport Rohingya “now”, but the government prevailed on the court to not pass any formal order, citing “international ramifications”. With this, the status quo continues even though the court gave the community liberty to approach i
1 comment
Click Here To Read more »