"Superconductivity and ferroelectricity in strontium titanate and related compundso" by Kamran Behnia (PSL Research University)

Wednesday, April 17, 2019 - 4:00pm to 5:00pm
Condensed Matter Physics Seminar

Superconductivity and ferroelectricity in strontium titanate and related compounds

Kamran Behnia

Ecole Supérieure de Physique et de Chimie Industrielles

PSL Research University, Paris, France


Long-range ferroelectric order is aborted in strontium titanate because of quantum fluctuations. The extremely large low-temperature dielectric constant elongates the effective Bohr radius to a micron. Consequently, removing one oxygen atom out of several tens of thousands suffices to turn the insulator to a metal with a sharp Fermi surface and a superconducting instability and intriguing features in charge transport below and above the degeneracy temperature.


Substituting a tiny fraction of strontium atoms with calcium stabilizes long-range ferroelectric order. Remarkably, dilute superconductivity and dilute ferroelectricity coexist in a narrow window of doping in Sr1-xCaxTiO3-d. With increasing carrier concentration, the ferroelectric order is destroyed, and the superconducting critical temperature is enhanced near this quantum phase transition, confirming the suspected intimate link between dilute superconductivity and ferroelectric fluctuations.

4-330 PAB