Condensed-Matter Physics & Materials Science Seminar

"Quantiative Determination of the the Fluctuations Leading to Superconductivity in Cuprates"

Presented by Chandra Varma, University of California, Riverside

Tuesday, June 14, 2016, 1:30 pm — ISB Bldg. 734, Conf. Rm. 201 (upstairs)

I will report on Laser based ARPES of unprecedented accuracy and stability (taken by the group of Xingjiang Zhou, IOP, Beijing), together with a method of analysis suggested by me (and carried out with the group of Han-Yong Choi,
Asia Pacific Center for Theoretical Physics, Korea), to quantitatively extract the e↵ective frequency and momentum dependent interactions of fermions in both the full symmetry (normal) and the d-wave (pairing) symmetry in a family
of cuprates. The results are remarkably simple. The principal interactions are of the form:
I(k, k',w)~g0 [(1−cos(20k)cos(20'k)]F(w)
They are separable functions of momentum and frequency, the first part is the repulsive part and the second part is the attractive d-wave part. F(w) is nearly constant with an upper-energy cutoff of about 0.4eV. The dimensionless
coupling constant g0 ~ 0.15. These results were predicted in a theory of superconductivity and of the strange metal phase by quantum-critical fluctuation of loop-currents. They also rule out several alternatives proposed. I will also comment
on the normal state and superconductivity in the Fe-based compounds.

Hosted by: Peter D. Johnson

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