Superconducting Piezoelectric Effect

The magnetopiezoelectric effect (MPE) is a lattice distortion induced by the electric current in metals lacking both inversion symmetry and time-reversal symmetry. It was theoretically proposed [1,2] and experimentally observed [3-5] recently. These results revealed the potential of metals for piezoelectric devices. However, unlike the conventional piezoelectric effect, the MPE always accompanies Joule heating. This property makes the research and application of the MPE difficult.
In superconductors, the conventional piezoelectric effect is prohibited because the electric field should vanish due to the zero resistivity. On the other hand, the MPE-like response induced by the supercurrent can be realized. We call this phenomenon the superconducting piezoelectric effect (SCPE). The SCPE is more practical than the MPE because of the absence of Joule heating. Moreover, the SCPE is expected to be a probe of inversion and time-reversal symmetry breaking in superconductors, since it is sensitive to the symmetry breaking.
In this presentation, we formulate the SCPE and compare the calculations of the MPE and SCPE of a typical noncentrosymmetric superconductor, that is, a two-dimensional Rashba s-wave superconductor under in-plane magnetic field. The magnitude of the SCPE is comparable to that of the MPE, and thus our result implies the nonnegligible coupling between the supercurrent and lattice distortion in noncentrosymmetric superconductors. Furthermore, we clarify that finite total momentum of Cooper pairs plays a crucial role in the SCPE. In this setup, the helical superconducting state due to Cooper pairs with finite total momentum is inevitably stabilized. Our result reveals that the SCPE can be a direct probe of the helical superconductivity, which has been awaited for a long time.