Status  Confirmed 
Seminar Series  LPTENSHE 
Subjects  hepth 
Date  Thursday 28 September 2023 
Time  14:00 
Institute  LPENS 
Seminar Room  E244 (24 Rue Lhomond) 
Speaker's Last Name  Swain 
Speaker's First Name  Hareram 
Speaker's Email Address  
Speaker's Institution  Indian Inst. Tech., Madras 
Title  A semiholographic approach to strange metallic behaviour 
Abstract  "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 quasiparticle picture. In my talk, I will explain how we construct a semiholographic description for such behaviours where we propose an effective theory in which the electron of a twodimensional 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 Fermiliquidtype contributions to the selfenergy 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 linearinT 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 selfenergy. Interestingly, we explain the origin of the linearinT 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/overdoping with a fixed exponent over a wide range of temperatures. We further obtain a refined Planckian dissipation scenario. 
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