You’re violating CVX’s rules.
To enter this in CVX, the argument of log_det needs to be affine Hermitian definite (PSD). Given the ratio of variables between Qc and Qk, that is not the case. Indeed, Rk,c is neither convex nor concave even in the real scalar case, let alone general complex matrix case. For instance, the special case, log(1+x/(1+y)).