Superconductivity

Superconductivity at Low Density and its Relation to Superconductivity in Topological Materials

Speaker(s): 
Jonathan Ruhman
Dates: 
Thursday, July 6, 2017 - 4:00pm to 5:00pm

Topological superconductors are one of the most exotic states predicted for electronic matter. Recently a new family of superconductors, which appear to be promising candidates of these exotic states, have been discovered in material with topological band structures. The organizing idea is doping a...

Polaron-Plasmon Superconductivity in Strontium Titanate

Speaker(s): 
Alex Edelman
Dates: 
Wednesday, June 7, 2017 - 4:00pm to 5:00pm

Strontium titanate is a bulk insulator that becomes superconducting at remarkably low carrier densities. Even more enigmatic properties become apparent at the strontium titanate/lanthanum aluminate (STO/LAO) interface and it is important to disentangle the effects of reduced dimensionality from the poorly-understood pairing mechanism. Recent experiments measuring the surface photoemission spectrum[1] and bulk tunneling spectrum[1] have found a cross-over, as a function of carrier density, from a polaronic regime with substantial spectral weight associated with strongly...

Potential Inhomogeneities in Presence of Strong Interactions: Birth and Death of Superconductors

Speaker(s): 
Rajdeep Sensarma
Dates: 
Thursday, November 3, 2016 - 4:00pm to 5:00pm

Strong repulsive interactions and potential in homogeneities both tend to localize Fermions on a lattice and lead to loss of superconductivity. The natural question that comes up is whether they compete or complement each other when both are present in a system at the same time. In this talk, we will use a effective Hamiltonian approach which treats both interactions and in homogeneities on the same footing to look at two systems: (a) the Ionic Hubbard Model at half-filling, where a staggered potential on a bipartite lattice competes with interactions to...

Rajdeep Sensarma (TIFR): Potential Inhomogeneities in Presence of Strong Interactions: Birth and Death of Superconductors

Strong repulsive interactions and potential in homogeneities both tend to localize Fermions on a lattice and lead to loss of superconductivity. The natural question that comes up is whether they compete or complement each other when both are present in a system at the same time. In this talk, we will use a effective Hamiltonian approach which treats both interactions and in homogeneities on the same footing to look at two systems: (a) the Ionic Hubbard Model at half-filling, where a staggered potential on a bipartite lattice competes with interactions to delocalize charge and give birth to a novel superconductor. The superconducting Tc scales with the bandwidth of the system and shows a non-monotonic behaviour with the staggered potential, (b) the disordered Hubbard model away from half-filling, where weak disorder competes with strong interaction to preserve superconductivity, but strong disorder complements interactions leading to sudden death of superconductivity in this system.

Swing-Dancing Electron Pairs

  • By Aude Marjolin
  • 13 May 2015

A research team led by PQI faculty Jeremy Levy has discovered electrons that can "swing dance". This unique electronic behavior can potentially lead to new families of quantum devices.

Superconductors, materials that permit electrical current to flow without energy loss, form the basis for magnetic resonance imaging devices as well as emergingtechnologies such as quantum computers. At the heart of all superconductors is the bunching of electrons into pairs.

The work, done in collaboration with researchers from the University of Wisconsin-Madison and the U.S. Naval Research Laboratory, was published May 14 in the journal Nature.