title: Manifestation of magnetic quantum fluctuations in the dielectric properties of a multiferroic.
abstract: Insulating magnets can display novel signatures of quantum fluctuations as similar to the case of metallic magnets. However, their weak spin-lattice coupling has made such observations challenging. Here we find that antiferromagnetic (AF) quantum fluctuations manifest in the dielectric properties of multiferroic Ba2CoGe2O7, where a ferroelectric polarization develops concomitant to an AF ordering. Upon application of a magnetic field (H), dielectric constant shows a characteristic power-law dependence near absolute zero temperature and close to the critical field Hc=37.1 T due to enhanced AF quantum fluctuations. When H>Hc, the dielectric constant shows the temperature-dependent anomalies that reflect a crossover from a field-tuned quantum critical to a gapped spin-polarized state. We uncover theoretically that a linear relation between AF susceptibility and dielectric constant stems from the generic magnetoelectric coupling and directly explains the experimental findings, opening a new pathway for studying quantum criticality in condensed matter.
authors: 1] CeNSCMR, Department of Physics &Astronomy, Seoul National University, Seoul 151-747, Korea [2].
authors: Jae Wook
authors: JW
authors: Kim
authors: CeNSCMR, Department of Physics &Astronomy, Seoul National University, Seoul 151-747, Korea.
authors: Seunghyun
authors: S
authors: Khim
authors: CeNSCMR, Department of Physics &Astronomy, Seoul National University, Seoul 151-747, Korea.
authors: Sae Hwan
authors: SH
authors: Chun
authors: 1] National High Magnetic Field Laboratory (NHMFL), Florida State University, Tallahassee, Florida 32310, USA [2].
authors: Y
authors: Y
authors: Jo
authors: National High Magnetic Field Laboratory (NHMFL), Florida State University, Tallahassee, Florida 32310, USA.
authors: L
authors: L
authors: Balicas
authors: Department of Physics &Astronomy and Rutgers Center for Emergent Materials, Rutgers University, Piscataway, New Jersey 08854, USA.
authors: H T
authors: HT
authors: Yi
authors: Department of Physics &Astronomy and Rutgers Center for Emergent Materials, Rutgers University, Piscataway, New Jersey 08854, USA.
authors: S-W
authors: SW
authors: Cheong
authors: NHMFL, Los Alamos National Laboratory (LANL), Los Alamos, New Mexico 87545, USA.
authors: N
authors: N
authors: Harrison
authors: Theoretical Division, LANL, Los Alamos, New Mexico 87545, USA.
authors: C D
authors: CD
authors: Batista
authors: Department of Physics, Sungkyunkwan University, Suwon 440-746, Korea.
authors: Jung Hoon
authors: JH
authors: Han
authors: 1] CeNSCMR, Department of Physics &Astronomy, Seoul National University, Seoul 151-747, Korea [2] Institute of Applied Physics, Seoul National University, Seoul 151-747, Korea.
authors: Kee Hoon
authors: KH
authors: Kim