Dresden 2017 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 69: Focus Session: Superconductivity in the Vicinity of a Quantum Critical Point
TT 69.2: Invited Talk
Thursday, March 23, 2017, 15:30–16:00, HSZ 03
Quantum Criticality in Cuprate and Iron Based Superconductors — •Antony Carrington — University of Bristol, U.K.
I will review experiments which show that BaFe2(As1−xPx)2 is perhaps the best example of a quantum critical superconductor with a high Tc. Quantum oscillation cyclotron mass, specific heat and magnetic penetration depth are all strongly enhanced over a narrow range of x. Interestingly this increase in mass does not influence either the lower or upper critical fields in the expected way.
I will also discuss the applicability of quantum criticality to the cuprates. By measuring quantum oscillations in YBa2Cu4O8 under hydrostatic pressure we are able to show that the quasiparticle mass decreases as maximum Tc is approached. This result is opposite to the behaviour found when YBa2Cu3O7−δ is tuned towards maximum Tc by oxygen doping. Our results suggest that the proximity of the CDW end point to the maximum in Tc with doping is coincidental and that therefore quantum fluctuations of the CDW order do not boost Tc in the cuprates.