  Parity and time-reversal violating electric dipole moment (EDM) of $^{171}$Yb
is calculated accounting for the electron correlation effects over the
Dirac-Hartree-Fock (DHF) method in the relativistic Rayleigh-Schr\"odinger
many-body perturbation theory, with the second (MBPT(2) method) and third order
(MBPT(3) method) approximations, and two variants of all-order relativistic
many-body approaches, in the random phase approximation (RPA) and
coupled-cluster (CC) method with singles and doubles (CCSD method) framework.
We consider electron-nucleus tensor-pseudotensor (T-PT) and nuclear Schiff
moment (NSM) interactions as the predominant sources that induce EDM in a
diamagnetic atomic system. Our results from the CCSD method to EDM ($d_a$) of
$^{171}$Yb due to the T-PT and NSM interactions are found to be $d_a = 4.85(6)
\times 10^{-20} \langle \sigma \rangle C_T \ |e| \ cm$ and $d_a=2.89(4) \times
10^{-17} {S/(|e|\ fm^3)}$, respectively, where $C_T$ is the T-PT coupling
constant and $S$ is the NSM. These values differ significantly from the earlier
calculations. The reason for the same has been attributed to large correlation
effects arising through non-RPA type of interactions among the electrons in
this atom that are observed by analyzing the differences in the RPA and CCSD
results. This has been further scrutinized from the MBPT(2) and MBPT(3) results
and their roles have been demonstrated explicitly.
