ass5: Look at Ozcan's results

superconductivity_assignment5_kvkempen.tex

@@ -212,7 +212,29 @@ They are, however, kept constant, and $\lambda$ is what is varied by changing th
 With knowledge about $\lambda(0)$ from other sources, $\lambda(T)$ is determined by determining $\Delta \lambda$ from $\delta f$.
 Now the superfluid density can be determined.
 
+In \cite{ozcan}, heavy-fermion superconductor \ce{CeCoIn5} is investigated using the TDO technique to measure its penetration depth.
+It is an unconventional superconductor, and the question is what type of wave-symmetry it exhibits.
+The paper found a non-linear $\lambda(T)$ relation.
+See figure \ref{fig:linear-lambda} for their results.
+They do conclude that the material is in a $d_{x^2-y^2}$ superconductor ground state.
+I would expect there to be no nodes in the band gap energy, in this case, which however is the case.
+The authors also seem puzzled at the beginning.
+They suspect strong-scattering impurities to alter the $\lambda(T)$ relation.
+To exclude this possibility, they checked a couple of possible explanations.
+Purity was checked and impurity content was determined to be a factor 100 smaller than the deviation in $\lambda(T)$ would imply.
+Other theories were also ruled out, on impossibility of far-fetchedness.
+They conclude by proposing non-Fermi-liquid renormalisation in both the normal and superconducting state of \ce{CeCoIn5} to take place, yielding the well fitting relation as seen in the inset of figure \ref{fig:linear-lambda}.
+This means that their would be quantum criticality in the superconducting state, i.e. a phase transition at zero temperature.
+That would be exotic.
+In conclusion, the behavior of \ce{CeCoIn5} was not explained with certainty at the point this paper was published (2003), although quantum criticality was a possibility.
+However, years later (2014), further research supports their hypothesis \cite{paglione_quantum_2016}.
 
+\begin{figure}
+	\centering
+	\includegraphics[width=.6\textwidth]{ozcan-linear.png}
+	\caption{For \ce{CeCoIn5}, $\lambda(T) \propto T^2/(T-T^*)$ is plotted in the main plot. In the inset, the concluding hypothesis of the authors \cite{ozcan} is presented, i.e. $\lambda(T) \propto T^{1.5}$.}
+	\label{fig:linear-lambda}
+\end{figure}
 
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