1. The electron EDM search in solid ferroelectric Eu 0.5 Ba 0.5 TiO 3 Alex Sushkov Steve EckelSteve Lamoreaux

2. The Yale experiment Steve Eckel vacuum pumps electronics EDM experiment enclosed in magnetic shielding liquid helium cryostat 2

3. The idea for a solid-state search 3

4. atomic EDM 4

5. The idea for a solid-state search atomic EDM temperature polarization 5

6. The idea for a solid-state search atomic EDM temperature polarization magnetic dipole moment of one atom atom density magnetization EDM vector has to point along the spin 6

7. The idea for a solid-state search 7

8. Europium Eu 2+ ground state: 8 S 7/2 (L=0, S=7/2, J=7/2), configuration: [Xe] 4f 7 The electrons with unpaired spins 8

9. Ferroelectric Eu 0.5 Ba 0.5 TiO 3 : the perovskite crystal structure O 2- Ti 4+ Eu 2+ or Ba 2+ T > T c (e) : dielectric cubic symmetry, effective electric field E * = 0 9

10. Ferroelectric Eu 0.5 Ba 0.5 TiO 3 : the perovskite crystal structure O 2- Ti 4+ Eu 2+ or Ba 2+ T < T c (e) : ferroelectric symmetry broken, effective electric field E *  10 MV/cm 10

11. The effective electric field in Eu 0.5 Ba 0.5 TiO 3 E *  10 MV/cm E applied = 0 11 [PRA 81, 022104 (2010)]

12. Making Eu 0.5 Ba 0.5 TiO 3 ceramics Solid-state reaction at 1200 C in hydrogen/argon atmosphere First time this material has been synthesized and studied 12 [Nature Materials, July 2010]

13. Crystal structure of Eu 0.5 Ba 0.5 TiO 3 X-ray diffraction spectra Cubic (perovskite) structure 13

14. Multiferroic properties of Eu 0.5 Ba 0.5 TiO 3 magnetic moment of Eu 2+ ion density of Eu 2+ ions magnetic ordering temperature Magnetic susceptibility measurement 14 MultiferroicThe EDM experiment is in the paramagnetic phase

15. EDM experiment schematic 2  samples ground plane (graphite-painted) superconducting Pb foil with a slit for improving magnetic field homogeneity 2  layers of superconducting magnetic shielding (Pb foil) 3  SQUID pickup loops 2  high-voltage electrodes (graphite-painted) superconducting solenoid 15

16. Some very recent EDM data Time (s) SQUID signal (  0 ) EE M M EDM signature 16

17. Some very recent EDM data Time (s) SQUID signal (  0 ) EE M M displacement-current spikes during polarization switching 17

18. A few minutes of EDM data 18

19. Systematics Sample heating + magnetic field Magnetoelectric effect: P 2 M 2 No leakage currents No Berry’s phase No interference from external magnetic fields E applied = 0 superconducting magnetic shielding Beam/cell systematics we don’t have to deal with: Systematics we have to deal with: Need absolute magnetic field control at 100 nG level to suppress these to  10 -28 e  cm

20. Sample heating + magnetic field H Reverse sample polarization  sample heats up!  sample permeability drops  sample magnetization drops  flux through the pickup loop drops  SQUID signal correlated with polarization reversal The good news: no systematic at H=0

21. The magnetoelectric effect thermodynamic free energy polarizationmagnetization applied electric field applied magnetic field the EDM term: violates P- and T-symmetries the magnetoelectric term: obeys P- and T- symmetries gives rise to magnetization: external magnetic field quadratic in while EDM is linear in BUT if the polarization reversal is imperfect, then we get a signal that mimics EDM

22. Magnetoelectric effect Magnetoelectric magnetization: external magnetic field The good news: no systematic at H=0

23. The sensitivity of electron EDM search magnetic field sensitivity: effective electric field: Electric dipole moment sensitivity temperature: Boltzmann’s constant Eu 2+ number density: Eu 2+ magnetic moment: Bottom line: After 1 hour of averaging:After 10 days of averaging: current best limit 23 [PRA 81, 022104 (2010)]

24. Summary First data run  10 -24 e  cm after a few minutes of data taking Modifications in progress:  sapphire ground plane  magnetic shielding to conduct heat away from the sample to reduce background magnetic field