Abstract
It is difficult to imagine an isolated classical object which possess different moments of inertia when it is uniformly rotated about the same axis with the same angular frequency in opposite, clockwise and counterclockwise, directions. We argue that due to quantum effects, certain (semi-) conductors should exhibit asymmetry in their mechanical and conducting properties with respect to the opposite rotations. We show that a cylinder made of a suitably chosen semiconductor, coated in a metallic film and placed in the magnetic-field background, can serve as a “rotational diode”, which conducts electricity only at a specific range of angular frequencies. The critical angular frequency and the direction of rotation can be tuned with the magnetic field’s strength. Mechanically, the rotational diode possesses different moments of inertia when rotated in clockwise and counterclockwise directions. These effects emerge as a particularity of the Fermi-Dirac statistics of electrons in rotating conductors.
Highlights
Our daily-life experience tells us that any physical body has the same moments of inertia with respect to rotations in clockwise and counterclockwise directions
We show that this statement is no more correct at the quantum level if the statistical quantum effects of electronic systems are taken into account
The latter example provides some hope that the change in the clockwise/counterclockwise moments of inertia may be within experimental reach, despite it constituting a negligible fraction of the total moment of inertia of the system, ∆Ie.m./Ieto.mt . 10−16
Summary
Our daily-life experience tells us that any physical body has the same moments of inertia with respect to rotations in clockwise and counterclockwise directions. We mention that our discussion has no direct relation to the Einstein–de Haas effect [2] (which demonstrates the appearance of a mechanical torque exerted by an external magnetic field on a ferromagnet) and the Barnett effect [3] (which reveals a reciprocal phenomenon: a mechanical rotation changes the magnetization of a spinning ferromagnet) These phenomena appear naturally as a consequence of the conservation of angular momentum. They demonstrate a close relationship between the magnetism, induced by the spin and the orbital motion of the electrons, and the mechanical rotation Both the Einstein–de Haas and Barnett effects are unusual under the time reversal transformation, maintaining the symmetry of the system under a clockwise/counterclockwise flip in the rotation sense (see, for example, the experimental work [16]). The absence of current density in the corotating frame, J = σE = 0, implies that the rotating conductor produces a radial electric field in the laboratory frame:. The width w of the surface layer is extremely small (w R), of the order of a few nanometers
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