## Phase Diagrams of Inhomogeneous Superconductors

#### Chuck Agosta - Clark University

Strong evidence of inhomogeneous superconductivity has been found in a number of crystalline organic superconductors. Weak evidence has been found in heavy fermion and pnictide superconductors. Most of the evidence has been based on phase diagrams built from various probes either directly or indirectly of the superconducting order parameter, in this case the Cooper pairs. Other possibly more compelling evidence comes from specific heat or NMR measurements. Below are examples of proposed phase diagrams.

As mentioned above the evidence is strongest in the crystalline organics. They are the most two dimensional and have the longest mean free paths of the materials that have been studied so far. More measurements in the pnictides may yield better results. It may help to intercalate some of the pnictides to make them more two dimensional, although that may reduce the mean free path. The optimal balance between lower dimensionality and mean free path remains a open question. There are many other systems that could be studied such as intercalated graphite, NbSe$_2$ and its variants, and possibly the cuprates. One would think the cuprates would be obvious candidates given their very high anisotropy, but for many of them the energy gap is prohibitively high to reach the magnetic fields necessary to reach the FFLO state.

All of the graphs above are normalized by the paramagnetic limit $H_P$. Also referred to as the Clogston Chandrasakhar limit a method of determining this value is found on this page.

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Last updated 11 Dec 2018
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