Fermion Condensation, T-Linear Resistivity, and Planckian Limit

Abstract

We explain recent challenging experimental observations of universal scattering rate related to the linear-temperature resistivity exhibited by a large corps of both strongly correlated Fermi systems and conventional metals. We show that the observed scattering rate in strongly correlated Fermi systems like heavy fermion metals and high-Tc superconductors stems from phonon contribution that induce the linear temperature dependence of a resistivity. The above phonons are formed by the presence of flat band, resulting from the topological fermion condensation quantum phase transition (FCQPT). We emphasize that so -called Planckian limit, widely used to explain the above universal scattering rate, may occur accidentally as in conventional metals its experimental manifestations (e.g. scattering rate at room and higher temperatures) are indistinguishable from those generated by the well-know phonons being the classic lattice excitations. Our results are in good agreement with experimental data and show convincingly that the topological FCQPT can be viewed as the universal agent explaining the very unusual physics of strongly correlated Fermi systems.

Violation of the Time-Reversal and Particle-Hole Symmetries in Strongly Correlated Fermi Systems: A Review

“…In addition, the universality, in turn, is due to the fact, that the considered fermion condensation phenomenon occurs due to the change of the topological class of the corresponding Fermi surface. This immediately implies the universality of both the above asymmetries as topology is one more milestone of contemporary physics-the topological class of an object can reveal a lot about its physical properties [1,[11][12][13][14]19,50]. We argue here, that existing microscopic approaches,-based either on model calculations within Hubbard and Kondo models or simulations (constructed actually from more sophisticated versions of the latter models) cannot describe adequately the appearance and destruction of asymmetric conductivity in solids.…”

“…We argue here, that existing microscopic approaches,-based either on model calculations within Hubbard and Kondo models or simulations (constructed actually from more sophisticated versions of the latter models) cannot describe adequately the appearance and destruction of asymmetric conductivity in solids. We speculate that the presented FC theory, which is based on general topological and symmetry arguments, can be well considered to be a candidate to explain not only the above discussed but many other properties of seemingly different physical objects from a uniform point of view [1,[11][12][13][14]19,[50][51][52]. To the best of our knowledge, the effective theories of gravity, even their quantum versions, cannot explain the baryon asymmetry, the existence of time arrow, the large entropy and other yet unexplained problems of contemporary cosmology and large-scale astronomy.…”

Mean-field theory for superconductivity in twisted bilayer graphene

“…The extreme limit would be an approximately flat band of size Ω FB , where the group velocity tends to zero. In such systems the critical temperature is a linear function of the coupling strength, T c = λΩ FB /π 2 [6,7], and quite high T c can be expected even without extra doping [8][9][10][11][12][13].…”

Planckian Dissipation in Metals

“…In [182] various non-Fermi liquid regimes are found in which the mass renormalization enforces a Planckian bound on physical transport lifetimes, as in our discussion in §3.2 and §3.4 above. Robustly Planckian physical lifetimes are obtained in [183] from a model with a smeared out Fermi surface, whose similarities to a phenomenological 'flat band' theory in which Planckian dissipation has also been analyzed [184] have been noted [185]. Controlled theories of a Planckian marginal Fermi liquid, considered in §3.4, were obtained in [186,187] by performing certain averages on a large N model of fermionic quantum criticality.…”