Non-Fermi Liquid Behavior in Heavy Fermion Systems

Schlottmann, P.

doi:10.1016/b978-0-444-63528-0.00002-4

Cited by 5 publications

(3 citation statements)

References 242 publications

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“…Actually, according to very general scaling considerations, a power-law behavior σ(T) ∝ T x signals a metal-insulator quantum phase transition 22 . The positive exponent contrasts with the negative values found in metallic materials where the quantum criticality is not due to the proximity of a metal-insulator transition but interfaces two different conducting states, such as in a magnetic/heavy fermion quantum phase transition 51,52 . The specific value x~+1 for SICO must be captured by an appropriate microscopic model (see below).…”

Section: Resultscontrasting

confidence: 60%

Quantum criticality in a layered iridate

et al. 2021

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Iridates provide a fertile ground to investigate correlated electrons in the presence of strong spin-orbit coupling. Bringing these systems to the proximity of a metal-insulator quantum phase transition is a challenge that must be met to access quantum critical fluctuations with charge and spin-orbital degrees of freedom. Here, electrical transport and Raman scattering measurements provide evidence that a metal-insulator quantum critical point is effectively reached in 5% Co-doped Sr2IrO4 with high structural quality. The dc-electrical conductivity shows a linear temperature dependence that is successfully captured by a model involving a Co acceptor level at the Fermi energy that becomes gradually populated at finite temperatures, creating thermally-activated holes in the Jeff = 1/2 lower Hubbard band. The so-formed quantum critical fluctuations are exceptionally heavy and the resulting electronic continuum couples with an optical phonon at all temperatures. The magnetic order and pseudospin-phonon coupling are preserved under the Co doping. This work brings quantum phase transitions, iridates and heavy-fermion physics to the same arena.

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Section: Resultscontrasting

confidence: 60%

Quantum criticality in a layered iridate

et al. 2021

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“…For instance, electric resistivity deviates from the ρ(T) ∝ T 2 temperature dependence, and specific heat C V (T) is no longer linearly temperature-dependent [4,[10][11][12]. Moreover, a variety of realistic materials exhibit NFL behaviors, which include but are not limited to cuprates [11,12], iron-pnictides and chalcogenides [13,14], and heavy-fermion compounds [10,15]. The superconducting phase emerges from a NFL normal state in these materials [10,13,16].…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, a variety of realistic materials exhibit NFL behaviors, which include but are not limited to cuprates [11,12], iron-pnictides and chalcogenides [13,14], and heavy-fermion compounds [10,15]. The superconducting phase emerges from a NFL normal state in these materials [10,13,16]. It is illuminating to understand their pairing mechanisms from studying the pairing from a unconventional metal which beyond Landau's Fermi liquid theory.…”

Section: Introductionmentioning

confidence: 99%

Two-stage superconductivity in the Hatsugai–Kohomoto-BCS model

et al. 2022

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Superconductivity in strongly correlated electrons can emerge out from a normal state that is beyond the Landau's Fermi liquid paradigm, often dubbed as "non-Fermi liquid". While the theory for non-Fermi liquid is still not yet conclusive, a recent study on the exactly-solvable Hatsugai-Kohomoto (HK) model has suggested a non-Fermi liquid ground state whose Green's function resembles the Yang-Rice-Zhang ansatz for cuprates [P. W. Phillips, L. Yeo and E. W. Huang, Nat. Phys. 16, 1175 (2020)]. Similar to the effect of on-site Coulomb repulsion in the Hubbard model, the repulsive interaction in the HK model divides the momentum space into three parts: empty, single-occupied and double-occupied regions, that are separated from each other by two distinct Fermi surfaces. In the presence of an additional Bardeen-Cooper-Schrieffer (BCS)-type pairing interaction of a moderate strength, we show that the system exhibits a "two-stage superconductivity" feature as temperature decreases: a first-order superconducting transition occurs at a temperature Tc that is followed by a sudden increase of the superconducting order parameter at a lower temperature T′ c < Tc. At the first stage, T′ c < T < Tc, the pairing function arises and the entropy is released only in the vicinity of the two Fermi surfaces; while at the second stage, T < T′ c, the pairing function becomes significant and the entropy is further released in deep (single-occupied) region in the Fermi sea. The phase transitions are analyzed within the Ginzburg-Landau theory. Our work sheds new light on unconventional superconductivity in strongly correlated electrons.

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Instabilities of a Fermi Gas with Nested Fermi Surfaces

Schlottmann

2017

Annalen der Physik

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The nesting of the Fermi surfaces of an electron and a hole pocket separated by a vector Q commensurate with the lattice in conjunction with the interaction between the quasiparticles can give rise to a rich phase diagram. Of particular importance is itinerant antiferromagnetic order in the context of pnictides and heavy fermion compounds. By mismatching the nesting the order can gradually be suppressed and as the Néel temperature tends to zero a quantum critical point is obtained. A superconducting dome above the quantum critical point can be induced by the transfer of pairs of electrons between the pockets. The conditions under which such a dome arises are studied. In addition numerous other phases may arise, e.g. charge density waves, non-Fermi liquid behavior, non-s-wave superconductivity, Pomeranchuk instabilities of the Fermi surface, nematic order, and phases with persistent orbital currents.

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Non-Fermi Liquid Behavior in Heavy Fermion Systems

Cited by 5 publications

References 242 publications

Quantum criticality in a layered iridate

Quantum criticality in a layered iridate

Two-stage superconductivity in the Hatsugai–Kohomoto-BCS model

Instabilities of a Fermi Gas with Nested Fermi Surfaces

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