Condensed Matter Seminar

Prof. Premala Chandra
Rutgers University

Thursday, November 12, 2008
1:00 pm in SPL 52

The J1-J2 Model: A Bridge between the Bronze and the Iron Ages of Superconductivity

Abstract: In this talk I will discuss the J1-J2 model and its modern impact on the iron-based superconductors.

The J1-J2 Heisenberg model was "born" twenty years ago in the early era of high temperature superconductivity as a simple example of a spin liquid. Although this model proved inutile for cuprate superconductivity, it had many spin-offs. These included the prediction of an emergent finite-temperature nematic Ising phase transition that was sought but not found in numerical simulations of the time.

Five years ago, state-of-the-art computational studies confirmed the presence of this fluctation-induced nematic Ising order. Then came the iron age, the discovery of superconductivity in iron-layered compounds. Here through local chemistry, the magnetic interactions are described by the J1-J2 model and there is an observable realization of the nematic Ising transition.

I will describe recent experiments that confirm the presence of nematic fluctuations in these materials, and will also discuss how the J1-J2 model provides a basis for linking the s+- superconducting order parameter with the original RVB hypothesis for cuprate superconductors.

Wikipedia Entry on Bronze:
Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive, but sometimes with other elements such as phosphorus, manganese, aluminium, silicon (..oxygen, strontium, ytterbium,lanthanum....)