Suggested search forPb207nuclear Schiff moment inPbTiO3

Abstract

We suggest two types of experiments, NMR and macroscopic magnetometry, with solid PbTiO3 to search for the nuclear Schiff moment of 207 Pb. Both kinds of experiments promise substantial improvement over the presently achieved sensitivities. Statistical considerations show that the improvement of the current sensitivity can be up to 10 orders of magnitude for the magnetometry experiment and up to 6 orders of magnitude for the NMR experiment. Such significant enhancement is due to the strong internal electric field of the ferroelectric, as well as due to the possibility to cool the nuclear-spin subsystem in the compound down to nanokelvin temperatures. PACS numbers: 11.30.Er, 32.10.Dk, 67.80.Jd The existence of permanent electric dipole moment (EDM) of a quantum particle requires that fundamental parity (P) and time-reversal (T) symmetries are violated. By the CPT-theorem, this would also mean the violation of the combined CP (charge conjugation-parity) symmetry. Studies of T and CP violation in Nature provide valuable information for the theories of baryogenesis, and for our understanding of fundamental interactions in general. Thus, considerable effort has been put into searches for EDMs of particles, atoms and molecules.The current experimental upper limit on the neutron EDM is d n ≤ 6.3 × 10 −26 e cm [1]. Experiments with paramagnetic atoms and molecules, the most sensitive of which was performed with Tl atoms [2], provide upper limit on the electron EDM, d e ≤ 1.6 × 10 −27 e cm. The most sensitive experiment with diamagnetic atoms is performed with 199 Hg vapor [3]; it gives the upper limit on the EDM of 199 Hg atom d( 199 Hg) ≤ 2.1 × 10 −28 e cm. This EDM is mainly induced by the nuclear Schiff moment, S, which is usually defined by the P-and T-odd electrostatic potential it generates [4]:Atomic calculations [5,6] [12]. Since Xe atoms are diamagnetic, the measurement is mainly aimed at the 129 Xe nuclear Schiff moment. By statistical considerations only, the sensitivity of the experiment is d( 129 Xe) ∼ 3 × 10 −37 e cm for 10 days of averaging [12]. Taking into account the smaller nuclear charge of Xe, this effectively means improvement by 8 orders of magnitude when compared to the present result (2) for 199 Hg. The limitations because of the systematic effects are also discussed in Ref. [12]. The solid state experiment with gadolinium garnet, recently suggested by Lamoreaux [13] to measure the electron EDM, promises 5 order of magnitude improvement over the current Tl result (statistical estimate corresponding to 10 days of averaging.)In the present paper we suggest to use ferroelectric PbTiO 3 to measure Schiff moment of 207 Pb nucleus. Possibility to measure the macroscopic magnetization induced by electric field, as was suggested by Lamoreaux for gadolinium garnets [13], looks most promising because of the large internal electric field in ferroelectric. In addition, the nuclear-spin subsystem of the compound can be magnetically cooled down to nanokelvin temperatures. For a 10-day averaging, statisti...

Investigating the nuclear Schiff moment of207Pb in ferroelectric PbTiO3

“…It is recommended that the present estimate of the energy shift in Eq. (13) supercede the earlier result of [21].…”

“…The matching is done at an intermediate distance in the cluster between the O 2− ions and the central Gd 3+ ion. In the present paper we perform a much more accurate calculation as compared to the estimate of [21]. It is well known that relativistic effects are very important for the calculation of the NSM.…”

“…In Ref. [21], Eq. (5) was applied to calculate the energy shift using a value of β = −0.29 estimated previously for GdO 8 clusters [13].…”

“…The material was proposed for measuring the NSM in Ref. [21] where the first estimate of the expected effect for also performed. Experiments with this compound offer the possibilty of an improvement in sensitivity to the NSM by several orders of magnitude in comparison with existing results [21,22,23,24,25].…”

Proposal for a Cosmic Axion Spin Precession Experiment (CASPEr)

“…In a ferroelectric, this displacement can be switched by an applied voltage; however, given the oscillating nature of the ALP-induced signal, it may not be necessary to modulate this displacement, in which case any polar crystal can be used. For ferroelectric PbTiO 3 , the effective electric field is E Ã ≈ 3 × 10 8 V=cm [41]. For other materials, where polarization is permanent, this may be higher by a factor of a few.…”