Electric symmetry breaking

Larter, R. Ortoleva, P. J. Theoret. Biol., "A Study of Instability to Electrical Symmetry Breaking in Unicellular Systems" (submitted for publication). 

The induced absorption band at 3 eV does not have any corresponding spectral feature in a(co), indicating that it is most probably due to an even parity state. Such a state would not show up in a(co) since the optical transition IAK - mAg is dipole forbidden. We relate the induced absorption bands to transfer of oscillator strength from the allowed 1AS-+1 (absorption band 1) to the forbidden 1 Ak - mAg transition, caused by the symmetry-breaking external electric field. A similar, smaller band is seen in EA at 3.5 eV, which is attributed to the kAg state. The kAg state has a weaker polarizability than the mAg, related to a weaker coupling to the lower 1 Bu state. 

This chapter is devoted to the behavior of double layers and inclusion-free membranes. Section II treats two simple models, the elastic dimer and the elastic capacitor. They help to demonstrate the origin of electroelastic instabilities. Section III considers electrochemical interfaces. We discuss theoretical predictions of negative capacitance and how they may be related to reality. For this purpose we introduce three sorts of electrical control and show that this anomaly is most likely to arise in models which assume that the charge density on the electrode is uniform and can be controlled. This real applications only the total charge or the applied voltage can be fixed. We then show that predictions of C < 0 under a-control may indicate that in reality the symmetry breaks. Such interfaces undergo a transition to a nonuniform state the initial uniformity assumption is erroneous. Most... 

If the nuclei occupy sites with symmetry axes lower than three-fold, the asymmetry of the electric field breaks the simple description in terms of m7 values, and all twelve possible transitions may be observed. Their positions and intensities are now a function of e qQ and... 

The inversion operation i which leads to the g/u classification of the electronic states is not a true symmetry operation because it does not commute with the Fermi contact hyperfine Hamiltonian. The operator i acts within the molecule-fixed axis system on electron orbital and vibrational coordinates only. It does not affect electron or nuclear spin coordinates and therefore cannot be used to classify the total wave function of the molecule. Since g and u are not exact labels, it was realised by Bunker and Moss [265] that electric dipole pure rotational transitions were possible in ll], the g/u symmetry breaking (and simultaneous ortho-para mixing) being relatively large for levels very close to the dissociation asymptote. The electric dipole transition moment for the 19,1 19,0 rotational transition in the ground electronic state was calculated... 

Electrical and Magnetic Properties of MEM(TCNQ)2 Contrary to TEA(TCNQ)2, the chain structure in MEM(TCNQ)2 [24,25] is found to go discontinously from a very weak dimerization above 335 K to a strong dimerization below 335 K. This is a first-order transition which is reminiscent here of a 4kF transition, although there is still no symmetry breaking [28]. An additional tetramerization also starts to develop continuously below 19 K. This last transition, which now involves symmetry breaking, can be identified with a true second-order 2kF transition [17,18,28] (see Section 7). 

In order to illustrate the analogy between symmetry breaking and phase transitions, we briefly review the main results for the two-electron atoms in the Hartree-Fock (HF) approximation [7]. In the HF approximation at the D —> oo limit, the dimensional-scaled effective Hamiltonian for the two-electron atom in an external weak electric field can be written as [38,39]... 

Y is again the weak hypercharge Y = 2 q — tz), which is 1/3 for u and d, 4/3 for Uij and —2/3 for dij. This ensures that the correct electric charges for the coupling of the up quark (+(2/3)e) and the down quark (—(l/3)e) to the field is obtained. The Yukawa term >CYuk.,g( ), which assigns masses to the quarks upon symmetry breaking, differs from that for the leptons, since both the up and the down quark carry masses ... 

Many of the CC theoretical predictions, such as control of atomic and molecular processes via N versus M photon transitions [137], have been tested and demonstrated experimentally [138-146]. CC methods have also proved to be valid in the context of solid-state systems. In particular, it was shown that excitation by N and M multiphoton processes, having opposite parities, leads to symmetry breaking and the generation of DC electric currents [147-151]. These predictions have been confirmed experimentally in a number of semiconductors [152-155]. Similar techniques were shown to lead to the control of phonon emission [156] or injection of spin currents [157]. 

L. Eriksson, N. Salhi-Benachenhou and O. Goscinski Symmetry Breaking in Charge-Transfer Compounds. The Efifects of Electric Eields and Substituents on the Properties of Bipyrazine Cations Mol. Eng. 4, 339 (1995). 

The ferroelectric materials show a switchable macroscopic electric polarization which effectively couples external electric fields with the elastic and structural properties of these compounds. These properties have been used in many technological applications, like actuators and transducers which transform electrical signals into mechanical work [72], or non-volatile random access memories [73]. From a more fundamental point of view, the study of the phase transitions and symmetry breakings in these materials are also very interesting, and their properties are extremely sensitive to changes in temperature, strain, composition, and defects concentration [74]. 

In the absence of any mirror symmetry breaking by the rubbing process, the molecular and the sample frame are identical. In this case, the experimental intensities for 100% linearly polarized x-rays with the electric field vector oscillating along the x, y, and 2 axes are directly proportional to the... 

Appendix B Symmetry Breaking by Uniform Linear Electric... 

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