Ion implantation as a tool to increase the internal pressure in a superconductor & hence its critical temperature drastically

1.5 Mev Ar-irradiation of 2.5 × 1015ions/cm2 at IUAC, New Delhi, was used, hoping to record radiation damage in Fe-superconductors, as these metallic High Temperature Superconductors (HTSCs) are promising superconducting wire materials. But, to our surprise, the irradiation increased the Superconducting Critical Temperature (Tc) by about 49%, never observed earlier.
Our Ba(Fe0.943Co0.057)2As2single crystal [1,2] HTSC samples were of 1.7–3 mm length and 1–2 mm width, with∼ 200 micron thickness. C-axis was along the thickness, and the radiation beam came along this direction. Our ion range (R from SRIM calculation = 0.903 μm) was much shorter than the thickness, making it a case of ion implantation. The Figure shows data for 0 T and 4 T measurements. Here, Tc(onset) from electrical resistivity measurement under zero magnetic field proved increase of Tc from 15.6 K to 23.8 K i.e. by 8.2 K A peak in the imaginary part of magnetic susceptibility (χʺ) indicates Tc. The un-radiated (UR) sample shows Tc = ~ 16 K from its χʺ peak. After our Ar-irradiation, this sample “Ba5.7Co AR”, shows a confirming increase of Tc to ~ 24 K. Onset Tc increased also by ∼ 8 K from its initial value of ∼ 17 K as measured from the real part of the magnetic susceptibility. ... mehrIt is satisfying that the ZFC magnetization data indicated an increase of Tc (onset) from 17 K to 25 K. These 4 independent measurements strongly prove that this presently discovered ~ 49% increase of Tc is correct.
Clearly, none of the known mechanisms of Tc increase can explain this ~ 49% increase of Tc due to our Ar ion irradiation. A new and exotic explanation follows. Being insoluble the Ar atoms precipitate often as high pressure (HP) miniature gaseous bubbles. Such bubble formation is well-known from observations in the walls of nuclear reactors. These HP bubbles exert a large compressive strain on the lattice of the superconductor. This additional strain increases the superconducting transition temperature by ∼ 49 % as can be shown from Tc vs. pressure data. Moreover, the same Ar implantation by us into non-superconducting BaFe2As2 single crystals induced 20 K superconductivity, a proof of the new explanation. We look forward through ibmec2026_iuac for collaboration and support for further work into this doubly fascinating area.