Theoretical study of upper critical magnetic field in superconductor UTe₂

This study focuses on the theoretical investigation of temperature-dependent upper critical magnetic field (H_C2) of uranium ditelluride (UTe₂) superconductor. The main objective of this work is to show the temperature dependence of the upper critical magnetic field of superconducting UTe₂ by using the Ginzburg-Landau (GL) phenomenological equation as it is the best model to describe the parameters. We demonstrated a clear correlation between the upper critical magnetic fields Hjja_C2ðTÞ, Hjjb C2 Tð Þ; Hjjc C2ðTÞ and Hjjc C2 ðTÞ along the three crystallography directions (a, b, c axis and parallel to ab-plane), respectively, the GL coherence length (nGLðTÞ) and GL penetration depth (kGLðTÞ), we have also derived the expression for Ginzburg-Landau characteristic parameter (jGLðTÞÞ. We have plotted the phase diagrams of H_C2 , nGL , kGL and jGL versus temperature for UTe₂ . It is observed that the upper critical magnetic field and GL characteristic parameter decrease as temperature increases and finally vanish at the superconducting critical temperature of UTe₂ , which means the superconductivity will be suppressed at the critical temperature. At the same time, the GL coherence length and GL penetration depth increase as temperature increases and goes to infinity at the superconducting critical temperature of UTe₂ , and results in the breakdown of Cooper pairs and the cessation of superconductivity. Our findings are in agreement with previous experimental results. (author)