Jahn–Teller and Pseudo-Jahn–Teller Effects: From Particular Features to General Tools in Exploring Molecular and Solid State Properties

Abstract

Fe atom results in their nonzero overlap producing a covalence contribution to this bonding. Reprinted with permission from ref 5. Copyright (2006) I. B. Bersuker. Chemical Reviews pubs.acs.org/CR Review

The Jahn–Teller and Pseudo-Jahn–Teller Effects: A Unique and Only Source of Spontaneous Symmetry Breaking in Atomic Matter

“…Indeed, "in quantum-mechanical description of the motions of the electrons and nuclei, the notion of space configuration is introduced in the adiabatic approximation, in which it is assumed that due to the huge difference between the masses of electrons and nuclei, the fast moving electrons follow adiabatically the much slower nuclear motions. Here adiabatic means that at each instantly fixed nuclear configuration, a stationary electronic charge distribution is achieved, The system in a stable nondegenerate electronic state has a relatively low-lying (at the energy gap ∆ 0 ) double-degenerate excited state with a strong JTE-induced distortion, its stabilization energy E JT being larger than ∆ 0 , thus producing a more stable ground state distorted along Q; this is the hidden-JTE; (b) In a system with a similar nondegenerate ground state as in (a), the excited state is nondegenerate, too, but there is a near-neighbor next excited state (with a relatively small energy gap between them ∆ 12 ), which allows for their PJT coupling with E PJT > ∆ 0 , resulting in a distorted ground state, similar to the case (a); this is the hidden-PJTE [9,14,15].…”

“…This is the pseudo JTE (PJTE) (see in refs. [7][8][9]13]). More recently, it was also shown that there may be "hidden" JTE and "hidden" PJTE when the state under consideration is neither degenerate, nor pseudodegenerate, but there is a strong JTE or PJTE in the excited state that penetrates the ground state [14,15].…”

“…Actually, degeneracy and pseudodegeneracy are the only sources of SSB in the whole spectrum of transformations in matter from elementary particles to nuclei, to atoms, molecules, and solids" [10]. Figures 1-3 show some simple illustrative features of the JTE, PJTE, hidden-JTE, and hidden-PJTE (for more information see [7][8][9][10][11]13,14]). Below we label this group of four JT effects as JTEs.…”

“…"SSB in matter are very important, as they are present (explicitly or implicitly) in the majority of processes, including a variety of physical, chemical, and biological phenomena based on molecular configuration instability, and all kinds of phase transitions [7][8][9], as well as in the very existence of some elementary massive particles [5,6]. With regard to the properties of atomic systems, SSB plays a fundamental role.…”

Unified Hamiltonian Formalism of Jahn–Teller and Pseudo-Jahn–Teller Problems in Axial Symmetries

“…6 Their consequences, termed JT and pJT effects, are commonly seen in spectroscopy, structural chemistry, solid-state physics, and optoelectronics. [7][8][9][10][11][12][13][14][15][16][17][18] The JT and pJT interactions belong to the broader category of vibronic interactions, since they involve interactions between electronic and vibrational degrees of freedom. 3,19 Naturally, accurate vibronic Hamiltonians for JT/pJT problems are of critical importance to simulate and understand the associated JT/pJT effects.…”