Principal variation search (sometimes equated with the practically identical NegaScout) is a negamax algorithm that can be faster than alpha–beta pruning.
However, its original formulation has practical issues (in particular, it relies heavily on an OPEN list for storage) and nowadays most chess engines still use a form of NegaScout in their search.
Most chess engines use a transposition table in which the relevant part of the search tree is stored.
NegaScout takes after SCOUT, invented by Judea Pearl in 1980, which was the first algorithm to outperform alpha–beta and to be proven asymptotically optimal.
The exact score is only needed for nodes in the principal variation (an optimal sequence of moves for both players), where it will propagate up to the root.
Since a zero window search is much cheaper due to the higher frequency of beta cut-offs, this can save a lot of effort.