A TI-polaron (translation-invariant
polaron
A polaron is a quasiparticle used in condensed matter physics to understand the interactions between electrons and atoms in a solid material. The polaron concept was proposed by Lev Landau in 1933 and Solomon Pekar in 1946 to describe an electro ...
) is a type of elementary
quasiparticle
In condensed matter physics, a quasiparticle is a concept used to describe a collective behavior of a group of particles that can be treated as if they were a single particle. Formally, quasiparticles and collective excitations are closely relate ...
in
solid-state physics
Solid-state physics is the study of rigid matter, or solids, through methods such as solid-state chemistry, quantum mechanics, crystallography, electromagnetism, and metallurgy. It is the largest branch of condensed matter physics. Solid-state phy ...
. The ground state of TI-polaron is a delocalized state of electron-phonon system: the probabilities of
electron's occurrence at any point of a space are similar. Both the electron density and the amplitudes of
phonon
A phonon is a collective excitation in a periodic, elastic arrangement of atoms or molecules in condensed matter, specifically in solids and some liquids. In the context of optically trapped objects, the quantized vibration mode can be defined a ...
modes (renormalized by an interaction with the electron) are delocalized. The concept of a ''polaron potential well'' (formed by local phonons) in which the electron is localized, i.e. self-trapped state is lacking. Accordingly, the induced polarization charge of the translation-invariant polaron is equal to zero.
The ground state energy of the translation-invariant polaron is lower than that of Pekar polaron and is E
0 = -0.125720 α
2 (for Pekar polaron E
0 = -0.10851128 α
2), where α is electron-phonon coupling.
TI-polarons can create bound TI-bipolaron states, which play an important role in the theory of superconductivity.
[V.D. Lakhno. Superconducting properties of 3D low-density TI-bipolaron gas. preprint, 2015, arXiv:1507.08510.]
References
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Quasiparticles