Reconsidering evidence of shift current in a ferroelectric charge-transfer complex

Abstract

In Nakamura et al.[1], the authors present evidence of shift current in the electronic ferroelectric tetrathiafulvalene-$p$-chloranil (TTF-CA). Since the bulk photovoltaic current in non-centrosymmetric crystals has two contributions, namely the ballistic and shift, we explain why the experimental data and analysis presented by the authors does not permit unambiguous identification of shift current, and is not consistent with the mechanism of shift.