JT polarons

In order to address the properties of a JT-polaron, we compare it with the two classes of polarons we have already presented. We use the phonon interaction of the molecular Holstein or Frohlich Hamiltonian, given by (7) and we compare it with a JT Hamiltonian,... 

The first numerical results from a strictly quantum mechanical calculation were given a few years ago [89]. In particular, P. Kornilovitch formulated a path integral representation of a three-dimensional JT polaron. Applying a QMC algorithm, he calculated the energy of the ground state, the DOS and the effective mass of a single... 

Fig. 6 The competition between pseudo JT polarons (structured in stripes) and free quasi-particles gives rise to the QCP at T, which is found at the normalized critical doping = / c = 1 and normalized critical pressure = e/e = 1. Here = 0.25 belongs to the doping for stripe formation, and Ec = 0.4 is the optimal microstrain at a maximum inferred from EXAFS data. After [113]...

In the polaron problem (or the single-electron system coupled with phonons), both spin degrees of freedom and the electron-electron interaction as described by are irrelevant. The first work on the JT polaron was done by Hock et al. [91] on the E b system [92] which, unfortunately, possesses a too simple internal structure to provide qualitatively different features from those of the H (8> a system. Several works have treated the second simplest E (S> e system and found a quantitative difference in the polaron effective mass from that in the H (gia system [63,93-98]. The r (g) f JT polaron has also been studied and the difference from that in the i (g e system is revealed [99-101]. 

Let us start with the E e JT polaron in the weak-coupling region (or for the case of small gEigie), in which the perturbation approach in momentum representation is useful. The thermal one-electron Green s function Gkya(ico ) with co the fermion Matsubara frequency is defined at temperature T by... 

By comparing the result of w /w for the infinite-site system obtained by VED [96] (see. Fig. 2), we are confident that the two-site calculation provides a reasonably good result for m /m in the whole range of g at least in the anti-adiabatic region of t/a>o. The relevance of the two-site calculation has also been seen in the Holstein model [78]. Thus we can expect that the same is true for the r (g) t JT polaron. In Fig. 3, we show the result of m/m for the T (g) r system solid curve) which is obtained in the anti-adiabatic region by implementing an... 

Fig. 2 Inverse of the polaron mass enhancement factor, m/m, as a function of for the T (8) a (HP Holstein polaron) and the (8) e JT polaron. In the latter, the result in the infinite chain d = 1) is compared with that in the two-site system as weU as the analytic result in (26). The anti-adiabatic condition of (Uo// = 5 is assumed...

Fig. 3 Inverse of the mass enhancement factor, mim, as a function of g

Due to huge dimensions of the Hilbert space for JT systems, it is quite difficult to treat many JT polarons even with state-of-the-art supercomputers. Therefore we... 

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