title: Ferroelectricity in an s=1/2 chain cuprate.
abstract: We report our discovery of ferroelectricity in the spiral-magnetic state in the quantum quasi-one-dimensional (1D) S=1/2 magnet of LiCu2O2. Electric polarization (P) emerges along the c direction below the spiral-magnetic order temperature, but changes from the c to a axis when magnetic fields (H) are applied along the b direction. We also found that P(c) increases with H(c), and P(a) appears with H(a). LiCu2O2 in zero field appears to be the first ferroelectric cuprate and also a prototypical example of the "1D spiral-magnetic ferroelectrics." However, the unexpected behavior in H may demonstrate the complexity of the ordered spin configuration, inherent in the 1D S=1/2 magnet of LiCu2O2.
authors.affiliation: Rutgers Center for Emergent Materials & Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.
authors.forename: S
authors.initials: S
authors.lastname: Park
authors.forename: Y J
authors.initials: YJ
authors.lastname: Choi
authors.forename: C L
authors.initials: CL
authors.lastname: Zhang
authors.forename: S-W
authors.initials: SW
authors.lastname: Cheong