Abstract
We uncover a fundamental effect of the QED vacuum in an external electromagnetic (EM) field. We show that the quantized vacuum of electrons is spin polarized by the EM field and manifests as a vacuum spin current. An experiment is proposed to measure the spin torque exerted by the spin current by measuring the twisted angle of the director axis of a nematic liquid crystal.
Highlights
Introduction.—The quantum nature of vacuum is a fascinating place to look for novel physical phenomena
In this Letter, we show that due to the renormalization effect of the spin-orbit coupling of the electrons, the quantized vacuum can become spin polarized in the presence of an applied EM field and results in a spin current; see Eq (25)
The spin current is given by the 3-tensor Jij 1⁄4 nvisj, where vi is the velocity of the electron, sj is the spin, n is the particle number density, and i, j 1⁄4 1, 2, 3 denotes the spatial directions
Summary
It was found that the vacuum fluctuations of boundary QED system in the presence of an external magnetic field result in a magnetization current near its boundary [3,4] This nontrivial electromagnetic response of the vacuum is due to the electric charges carried by the virtual electrons and positrons of the theory. In this Letter, we show that due to the renormalization effect of the spin-orbit coupling of the electrons, the quantized vacuum can become spin polarized in the presence of an applied EM field and results in a spin current; see Eq (25). ΣivμÞ; J0i 1⁄4 σi; ð1Þ in terms of a symmetrization of the velocity and the spin has been proposed by Rashba [5] This works well for a nonrelativistic system, the generalization to the relativistic case requires the use of a relativistic spin operator.
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