Olle Lexell, MPPAS

The AdS/CFT correspondence is a potentially powerful tool in describing condensed matter systems for which our current theoretical understanding is lacking. This is because it can be used to map a strongly coupled field theory to a weakly coupled gravitational theory. In this thesis I describe some aspects of the AdS/CFT correspondence and look at a top-down model. This model is built upon a large number of D3 and D5 branes with a D7 probe brane.

The goal is to see whether this model can be used to describe aspects of the strange metal phase that is found in layered high-temperature superconductors. Starting from a weakly coupled string theory setting I derive the temperature-dependence of a DC current in different regimes, as well as dispersion relations for electromagnetic fluctuations. There is a possibility of getting resistivity that matches the linear in T dependence for the resistivity in strange metals. This is done by adjusting the number of D5 branes depending on the temperature and the charge density, which is obtained holographically. With a particular choice of boundary conditions, plasmonic dispersion relations are found, as required. This is the first layered top-down model with this behaviour for the current available in its parameter-space. While it has not produced correct predictions without an adjustment of the parameter-space, the freedoms granted from the said parameter-space makes it possible that this model could describe other layered systems that lacks quasi-particles, and not just strange metals. ​