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Résumé |
"Strange metals" exhibit an anomalous temperature dependence of the low
temperature resistivity and the measurement of their spectral function via ARPES
indicates the breakdown of the conventional quasi-particle picture. In my talk, I
will explain how we construct a semi-holographic description for such behaviours
where we propose an effective theory in which the electron of a two-dimensional
band hybridizes with a fermionic operator of a critical holographic sector, while
also interacting with other bands that preserve quasiparticle characteristics.
Besides the scaling dimension $\nu$ of the fermionic operator in the holographic
sector, the effective theory has two dimensionless couplings $\alpha$ and $\gamma$
determining the holographic and Fermi-liquid-type contributions to the self-energy
respectively. In the case of DC conductivity that irrespective of the choice of
the holographic critical sector, there exists a ratio of the effective couplings
for which we obtain linear-in-T resistivity for a wide range of temperatures. This
scaling persists to arbitrarily low temperatures when $\nu$ approaches unity in
which limit we obtain a marginal Fermi liquid with a specific temperature
dependence of the self-energy. Interestingly, we explain the origin of the
linear-in-T resistivity and strange metallic behavior as a consequence of the
emergence of a universal form of the spectral function which is independent of the
model parameters when the ratio of the two couplings takes optimal values
determined only by the critical exponent. This universal form fits well with
photoemission data of copper oxide samples for under/optimal/over-doping with a
fixed exponent over a wide range of temperatures. We further obtain a refined
Planckian dissipation scenario. |
