Floriana Lombardi, Chalmers University of Technology, Göteborg

Jeudi 5 mars à 14h, amphi Holweck
Escalier c, 1 er ètage.

Restoring the Planckian regime via suppression of charge
order in an underdoped YBCO cuprate superconductor

The normal state of the cuprate high-temperature superconductors (HTS), near optimal
doping, is characterized by a linear temperature dependence of the resistivity which
persists at the lowest T, when superconductivity is suppressed. This “strange
metal” behavior has been found to be ubiquitous in strongly correlated electron
superconductors and it is typical of quantum systems dominated by strong
electron-electron correlations and characterized by a fundamental relaxation time
scale τ that solely depends on the absolute temperature T and constants of nature,
( where ћ and kB are the (reduced) Planck and Boltzmann constants). However, the
T-linear behavior is lost in the underdoped regime of HTS already below T 240 K,
and the explanation for this effect is still unknown. In this contribution we
present new data where we show that in highly strained, ultrathin and underdoped
YBa2Cu3O7-δ (YBCO) films the T-linear resistivity (Planckian regime) is restored by
the suppression of the CDW order in the YBCO a-axis direction, which we have
detected by Resonant Inelastic X-ray Scattering measurements. This observation
clearly points towards an intimate connection between the onset of CDW order and the
resistivity vs temperature behavior in HTS, a link that was missing until now. This
conclusion appears also consistent with the “strange metal” phase of HTS having its
origin in a Quantum Critical Point (QCT) at T = 0. The recovery of the strange metal
behavior in ultrathin underdoped YBCO films shows the dramatic role played by strain
and confinement to manipulate the ground state of HTS and to reshape the phase
diagram. Moreover we will also give example on how the interplay between the
strange metal phase superconductivity and CDW order is crucial to design YBCO
devices at the nanoscale like nanowires based single photon detectors.

Restoring the Planckian regime via suppression of charge order in an underdoped
YBCO cuprate superconductor

Authors : E. Andersson1, R. Arpaia1,2, M. Rossi2,†, R. Fumagalli2, E. Trabaldo1, N.
B. Brookes3, L. Braicovich2,3, G. Ghiringhelli2,4, U. Gran1, T. Bauch1 and F.
Lombardi1,*

1 Quantum Device Physics Laboratory, Department of Microtechnology and Nanoscience,
Chalmers University of Technology, SE-41296, Göteborg, Sweden

2 Dipartimento di Fisica, Politecnico di Milano, I-20133 Milano, Italy

3 ESRF, The European Synchrotron, F-38043 Grenoble, France

4 CNR-SPIN, Dipartimento di Fisica, Politecnico di Milano, I-20133 Milano, Italy


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