[Paper Review] Polarization of Dielectrics by Acceleration

L. A. Melnikovsky|arXiv (Cornell University)|May 4, 2005

Solar and Space Plasma Dynamics1 references4 citations

TL;DR

This paper proposes that acceleration induces electric polarization in dielectrics through two mechanisms: intrinsic dipole moments in accelerated molecules and collective quadrupole polarization due to medium inhomogeneity. It derives a gravitoelectric polarization effect in superfluid 3He, showing quantitative agreement with experimental second-sound electric field measurements, with the dominant contribution arising from normal fluid acceleration and phonon excitations.

ABSTRACT

We argue that acceleration induces electric polarization in usual dielectrics. Both accelerations in superfluid participate in the medium polarization. Excitations contribution to the polarization is calculated at low temperatures. Estimates of the effect show order of magnitude agreement with recent experimental results on electric effect of superflow.

Motivation & Objective

• To explain the experimentally observed electric field in superfluid 3He during second-sound propagation.
• To establish a theoretical framework for acceleration-induced polarization in dielectrics, extending the Stewart-Tolman effect to non-conducting media.
• To account for both single-particle dipole and collective quadrupole contributions to polarization in accelerating media.
• To estimate the magnitude of the effect and compare it with experimental data on superflow-induced electric fields.
• To unify the observed electric effects in superfluids under a single mechanism: acceleration-driven polarization via gravitoelectric and flexoelectric effects.

Proposed method

• Derives a modified polarization equation (Eq. 3) incorporating acceleration via the equivalence principle, introducing a gravitoelectric susceptibility γ.
• Applies macroscopic hydrodynamics to model superfluid and normal components, using velocity fields v_s and v_n to compute acceleration contributions.
• Calculates quadrupole moment density Q^{ij} from atomic-scale inhomogeneities, linking it to polarization via P_f^i = -1/6 ∂Q^{ij}/∂x^j.
• Estimates contact potential and electric field using surface double-layer contributions (Eq. 4), accounting for macroscopic field detection.
• Uses linearized hydrodynamics and phonon/roton excitation models to compute polarization from density and temperature gradients.
• Derives the total polarization as P_g + P_f, with P_g from acceleration (Eq. 12) and P_f from density inhomogeneity (Eq. 14), including roton contributions (Eq. 15).

Experimental results

Research questions

• RQ1 Can acceleration of a dielectric medium induce measurable electric polarization through intrinsic and collective mechanisms?
• RQ2 How do superfluid and normal components of 3He contribute to acceleration-induced polarization?
• RQ3 What is the relative contribution of phonons and rotons to the observed electric field in second-sound waves?
• RQ4 Can the theoretical prediction of acceleration-induced polarization quantitatively match recent experimental results on superflow electric effects?
• RQ5 What role does medium inhomogeneity play in generating macroscopic electric fields under acceleration?

Key findings

• The gravitoelectric contribution to the voltage across a second-sound wavelength is estimated as U_g ∼ −(ε−1)M/(12e) C T′, with C being specific heat and T′ the temperature amplitude.
• The contact potential contribution is quadratic in velocity and oscillates at double frequency, with U_c ∼ (π/180)(Zeρ^{1/3}/M^{1/3})(S²T′²)/(ρρ_n c²c₂²)(Δ/T), making it negligible in comparison to the linear gravitoelectric term.
• The dominant contribution to the electric field comes from the normal fluid acceleration, with γ_n ∝ ρ_n/ρ (1 − δW/(3c²) − C/(3σ)) in the polarization expression.
• The quadrupole contribution from phonons is estimated as P_f ∼ φ∇(ρ^{1/3} − ρ_n/(12ρ^{2/3})), with φ = Ze/(24M^{1/3}), showing dependence on density inhomogeneity.
• Roton contributions to the quadrupole moment are anisotropic and non-scalar, with Q^{ij} ∝ (w^i w^j /5c² − δ^{ij}w²/15c²), leading to orientation-dependent contact potential.
• The theoretical model shows order-of-magnitude agreement with experimental data on the electric effect of superflow, validating the acceleration-induced polarization mechanism.