  Chirality or the handedness of objects is of prime importance in life
science, biology, chemistry and physics. It is also a major symmetry ingredient
in frustrated magnets revealing spin-spiral ground states. Vector chiral
phases, with the twist (either clock- or counter clock-wise) between
neighbouring spins being ordered, but with disorder with respect to the angles
between adjacent spins, have been predicted almost five decades ago.
Experimental proofs, however, are rare and controversial. Here, we provide
experimental evidence for such a phase in LiCuVO$_4$, a one-dimensional quantum
magnet with competing ferromagnetic and antiferromagnetic interactions. The
vector chiral state is identified via a finite ferroelectric polarization
arising at temperatures well above the multiferroic phase exhibiting long-range
three-dimensional spin-spiral and polar order. On increasing temperatures, spin
order becomes suppressed at TN, while chiral long-range order still exist,
leaving a temperature window with chirality-driven ferroelectricity in the
presence of an external magnetic field.
