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Lia Krusin-Elbaum - IBM Research & CCNY Physics

How "strange metal" state in high temperature superconductors becomes conventional


Attention Jour inhabituel

Unconventional states of metals often emerge from a quantum critical point (QCP) - a zero temperature transition between different ground states of matter. Near QCP the standard Landau’s Fermi-liquid theory is violated due to quantum fluctuations. Whether the QCP physics can explain the mystery of unusual pseudogapped and "strange metal" non-Fermi-liquid states of high-Tc superconductors and their connection to the origins of high Tc is a fundamental question still under debate.

 

Experimentally, the putative QCP and its surroundings are masked by superconductivity and remain uncertain. In this talk I will discuss how by destroying superconductivity with ultrastrong magnetic field in cuprates we can map the crossover to the Fermi liquid (FL) in cuprates in the temperature-doping (T-p) space down to low temperatures. I will show that this crossover and the pseudogap (PG) boundary link in the quantum limit at a value of doping that consistently downshifts under magnetic field in unison with the reduction of Tc.

 

The effect of magnetic field is the key. In a field, the pseudogap boundary T* has scaling properties, and it develops a thermodynamic divergence in the quantum limit corresponding to a zero entropy jump. We conclude that quantum criticality, "strange metal" states and superconductivity in cuprates are intimately linked.

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