Optical and magnetic penetration depths under a modified electromagnetic coupling in charged bosonic condensates

Abstract

We establish the relation between optical condensate spectral weight and static magnetic screening in a proposed effective theory of charged bosonic condensates with an additional diamagnetic coupling. Starting from an explicit Ginzburg--Landau functional, we derive both the London equation and the transverse low-frequency conductivity. At fixed condensate parameter $q^2{n}_s/m^{\ast }$, the modified coupling doubles the inverse-square magnetic screening length and the optical condensate weight, giving ${\lambda }_{\mathrm{mag}}={\lambda }_{\mathrm{stiff}}={\lambda }_L/\sqrt{2}$, where ${\lambda }_L^{-2}={\mu }_0{q}^2{n}_s/m^{\ast }$. Their ratio is therefore unity in both the standard and modified local theories: it tests consistency between measurement methods but cannot distinguish the couplings. A structured comparison of published results for Nb, Pb, YBCO, MgB${}_2$, and Ba(Fe,Co)${}_2$As${}_2$ identifies the roles of sample matching, absolute calibration, nonlocality, and spectral-weight extraction. We formulate the requirements for a discriminating absolute-response experiment and discuss a complementary single-particle spectral prediction. The analysis separates experimentally accessible consistency checks from tests requiring independent information about condensate parameters or a different observable.

arXiv commentTo appear in Physics Open - Elsevier