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The electron EDM search in solid ferroelectric Eu 0.5 Ba 0.5 TiO 3

The electron EDM search in solid ferroelectric Eu 0.5 Ba 0.5 TiO 3. Alex Sushkov. Steve Eckel. Steve Lamoreaux. The Yale experiment. Steve Eckel. electronics. EDM experiment enclosed in magnetic shielding. vacuum pumps. liquid helium cryostat. The idea for a solid-state search.

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The electron EDM search in solid ferroelectric Eu 0.5 Ba 0.5 TiO 3

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  1. The electron EDM search in solid ferroelectric Eu0.5Ba0.5TiO3 Alex Sushkov Steve Eckel Steve Lamoreaux

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

  3. The idea for a solid-state search

  4. The idea for a solid-state search atomic EDM

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

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

  7. The idea for a solid-state search

  8. Europium The electrons with unpaired spins Eu2+ ground state: 8S7/2 (L=0, S=7/2, J=7/2), configuration: [Xe] 4f7

  9. Ferroelectric Eu0.5Ba0.5TiO3:the perovskite crystal structure O2- Ti4+ Eu2+ or Ba2+ T > Tc(e): dielectric cubic symmetry, effective electric field E* = 0

  10. Ferroelectric Eu0.5Ba0.5TiO3:the perovskite crystal structure O2- Ti4+ Eu2+ or Ba2+ T < Tc(e): ferroelectric symmetry broken, effective electric field E* 10 MV/cm

  11. The effective electric field in Eu0.5Ba0.5TiO3 E*  10 MV/cm Eapplied = 0 [PRA 81, 022104 (2010)]

  12. Making Eu0.5Ba0.5TiO3 ceramics Solid-state reaction at 1200 C in hydrogen/argon atmosphere First time this material has been synthesized and studied [Nature Materials, July 2010]

  13. Crystal structure of Eu0.5Ba0.5TiO3 X-ray diffraction spectra Cubic (perovskite) structure

  14. Multiferroic properties of Eu0.5Ba0.5TiO3 Magnetic susceptibility measurement magnetic moment of Eu2+ ion density of Eu2+ ions magnetic ordering temperature Multiferroic The EDM experiment is in the paramagnetic phase

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

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

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

  18. A few minutes of EDM data

  19. Systematics Systematics we have to deal with: • Sample heating + magnetic field • Magnetoelectric effect: P2M2 Need absolute magnetic field control at 100 nG level to suppress these to 10-28ecm Beam/cell systematics we don’t have to deal with: • No leakage currents • No Berry’s phase • No interference from external magnetic fields Eapplied = 0 superconducting magnetic shielding

  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 the EDM term: violates P- and T-symmetries thermodynamic free energy applied electric field applied magnetic field the magnetoelectric term: obeys P- and T-symmetries polarization magnetization 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 temperature: Boltzmann’s constant magnetic field sensitivity: Electric dipole moment sensitivity effective electric field: Eu2+ magnetic moment: Eu2+ number density: Bottom line: After 1 hour of averaging: After 10 days of averaging: current best limit [PRA 81, 022104 (2010)]

  24. Summary • First data run  10-24e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

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