Casimir torque

Torres-Guzmán, José C.; Mochán, W. Luis

doi:10.1088/0305-4470/39/21/s81

Cited by 22 publications

(24 citation statements)

References 17 publications

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“…It can also be expressed in terms of the reflection matrices of the two materials, as in Refs. [26,27]. In our regime of interest, the energy has sin 2 θ dependence to an excellent approximation, as in Fig.…”

Section: Casimir Interaction Between Two Infinite Slabsmentioning

confidence: 54%

Rotation of a liquid crystal by the Casimir torque

Somers

Munday

2015

Phys. Rev. A

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We present a calculation of the Casimir torque acting on a liquid crystal near a birefringent crystal. In this system, a liquid crystal bulk is uniformly aligned at one surface and is twisted at the other surface by a birefringent crystal, e.g. barium titanate. The liquid crystal is separated from the solid crystal by an isotropic, transparent material such as SiO2. By varying the thickness of the deposited layer, we can observe the effect of retardation on the torque (which differentiates it from the close-range van der Waals torque). We find that a barium titanate slab would cause 5CB (4-cyano-4 -pentylbiphenyl) liquid crystal to rotate by 10 • through its bulk when separated by 35 nm of SiO2. The optical technique for measuring this twist is also outlined.

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Section: Casimir Interaction Between Two Infinite Slabsmentioning

confidence: 54%

Rotation of a liquid crystal by the Casimir torque

Somers

Munday

2015

Phys. Rev. A

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“…In Eqs. (9) and (10), V and S are a volume and a surface of a ferrite sample, respectively. Vector n is the outwardly directed normal to surface S. The azimuthally unidirectional wave propagation of MDMs are observed in mechanically non-rotating quasi-2D ferrite disks.…”

Section: B "Sagnac Effect" In a Mdm Ferrite Diskmentioning

confidence: 99%

Quantization of magnetoelectric fields

Kamenetskii

2019

Journal of Modern Optics

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The effect of quantum coherence involving macroscopic degree of freedom, and occurring in systems far larger than individual atoms are one of the topical fields in modern physics. Because of material dispersion, a phenomenological approach to macroscopic quantum electrodynamics, where no canonical formulation is attempted, is used. The problem becomes more complicated when geometrical forms of a material structure have to be taken into consideration. Magnetic-dipolar-mode (MDM) oscillations in a magnetically saturated quasi-2D ferrite disk are macroscopically quantized states. In this ferrimagnetic structure, long-range dipole-dipole correlation in positions of electron spins can be treated in terms of collective excitations of a system as a whole. The near fields in the proximity of a MDM ferrite disk have space and time symmetry breakings. Such MDM-originated fieldscalled magnetoelectric (ME) fieldscarry both spin and orbital angular momentums. By virtue of unique topology, ME fields are different from free-space electromagnetic (EM) fields. The ME fields are quantum fluctuations in vacuum. We call these quantized states ME photons. There are not virtual EM photons. We show that energy, spin and orbital angular momenta of MDM oscillations constitute the key physical quantities that characterize the ME-field configurations. We show that vacuum can induce a Casimir torque between a MDM ferrite disk, metal walls, and dielectric samples. PACS number(s): 41.20.Jb, 71.36.+c, 76.50.+g I.

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“…Such an analytic form is presented in Ref. where an expression for the torque per unit area is given by

τ_{z} = - \frac{ℏ c}{2 π} \int_{0}^{\infty} d κ \times \frac{Δ r_{1} Δ r_{2} sin 2 θ e^{(- 2 κ L)}}{Δ r_{1} Δ r_{2} si {normaln}^{2} θ e^{(- 2 κ L)} + (1 - r_{1 x} r_{2 x} e^{(- 2 κ L)}) (1 - r_{1 y} r_{2 y} e^{(- 2 κ L)})},

where

Δ r_{1} = r_{1 x} - r_{1 y}, Δ r_{2} = r_{2 x} - r_{2 y}, κ = - i q,

and according to

r_{i a} = \frac{\frac{n_{i a} - 1}{n_{i a} + 1} [exp (- 2 κ n_{i a} L_{i}) - 1]}{1 - {(\frac{n_{i a} - 1}{n_{i a} + 1})}^{2} exp (- 2 κ n_{i a} L_{i})},

with

i = 1 ...

…”

Section: Casimir Torque Between Two Birefringent Platesmentioning

confidence: 99%

“…Besides, zero temperature assumption can single out the Casimir effect when it is dominated by the thermal effect. Though the practical experiment is usually performed at nonzero temperature , the Casimir torque at zero temperature can at least qualitatively illustrate the important features .…”

Section: Introductionmentioning

confidence: 99%

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Casimir torque between birefringent plates with metamaterials

Chen

Spence

2013

Phys. Status Solidi A

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We investigate the Casimir torque between two coaxial plates separated by a small gap, each with positive or negative refractive index. Starting from the existing formula of two plates both with positive refractive index, we use suitable approximations and limits to extend it to the negative refractive index case. The torque found between two plates both with negative refractive index shows similar behavior in rotational motion to the case where both plates have positive refractive index, i.e., their principal axes in both x and y directions rotate to align them in their stable equilibrium‐angle position of 0 or π, due to the “attractive torque“. The torque between two plates, one with positive and the other negative refractive index has a subtle behavior which depends on r value, the multiplication of the anisotropy for the plates. If r lies in the interval (−∞, −2), this system is identical to that where both plates carry positive or negative refractive index. However, if r lies in the interval [−2,−4/3], generally three new equilibrium points arise additional to the usual four of 0,π/2,π,3π/2, and the former three are all unstable while the latter four are all stable. If r lies in the interval (−4/3,0), a different rotational behavior occurs due to the “repulsive torque”, i.e., the principal axes of each plate increase their misalignment to avoid the unstable equilibrium positions 0 or π. These effects probably cannot be measured experimentally at present due to their requirement of a wide range of frequencies for negative refractive index and a very small gap between the two plates, but may be in future.

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Casimir torque

Cited by 22 publications

References 17 publications

Rotation of a liquid crystal by the Casimir torque

Rotation of a liquid crystal by the Casimir torque

Quantization of magnetoelectric fields

Casimir torque between birefringent plates with metamaterials

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