Discovery of superconductivity in a low carrier density system: Bismuth

Abstract: Bismuth(Bi) has played a very important role in uncovering many interesting physical properties in condensed matter research1 and continues to draw enormous scientific interests due to its anomalous electronic properties. Unlike metals where there is roughly one mobile electron per atom, in a semi-metal like Bi, the concentration of mobile electrons is extremely low (100,000 atoms share a single mobile electron). Hence, the superconductivity (SC) in bulk Bi is thought to be very unlikely at a currently achievable temperature (~40 mK). In this talk, I will describe the first-ever observation of bulk SC in Bi single crystals (99.9999%) below 530 mK under ambient pressure with an estimated critical magnetic field of 5.2 mT (one eighth of earth’s magnetic field) at absolute zero2. The standard models (superconductivity) cannot explain this phenomenon because the characteristic thermal energy is comparable to the Fermi energy in Bi and a new theory is necessary

Date and Time: 2018/03/02 16:00 Venue: CSB Seminar Hall
Speaker: Prof. S. Ramakrishnan Speaker - Affiliations: TIFR, India