Flat bands and enigma of metamagnetic quantum critical regime in Sr3Ru2O7

We analyze exciting recent measurements [Phys. Rev. Lett. 114 (2015) 037202] of the magnetization, differential susceptibility and specific heat on one dimensional Heisenberg antiferromagnet Cu(C 4 H 4 N 2 )(NO 3 ) 2 (CuPzN) subjected to strong magnetic fields. Using the mapping between magnons (bosons) in CuPzN and fermions, we demonstrate that magnetic field tunes the insulator towards quantum critical point related to so-called fermion condensation quantum phase transition (FCQPT) at which the resulting fermion effective mass diverges kinematically. We show that the FCQPT concept permits to reveal the scaling behavior of thermodynamic characteristics, describe the experimental results quantitatively, and derive for the first time the T − H (temperature-magnetic field) phase diagram, that contains Landau-Fermi-liquid, crossover and non-Fermi liquid parts, thus resembling that of heavy-fermion compounds.

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“…It is seen from Fig. that LFL regime occurs at

T ≪ H_{s} - H

, the crossover at

T \sim H_{s} - H

and the NFL one at

T ≫ H_{s} - H

, which is the case for HF compounds, behaving like HF superconductor β‐YbAlB 4 or the quasicrystal

{Au}_{51} {Al}_{34} {Yb}_{15}

.…”

Section: Scaling Of the Thermodynamic Propertiesmentioning

confidence: 86%

“…Fig. d shows the scaling behavior of the superconductor β‐YbAlB 4 . The fusion of the curves, corresponding to different magnetic fields into one is clearly seen.…”

Section: Thermodynamic Propertiesmentioning

confidence: 99%

Magnetic quantum criticality in quasi‐one‐dimensional Heisenberg antiferromagnet

et al. 2016

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“…We employ the model 28-35 based on vHs that induces a peak in the single-particle density of states (DOS) and leads a field-induced flat band. 39 At fields in the range B c1 < B < B c2 , the vHs is moved through the Fermi energy and the DOS peak turns out to be at or near the Fermi energy. A key point in this scenario is that within the range B c1 < B < B c2 , a repulsive interaction (e.g., Coulomb) is sufficient to induce FC and formation of a flat band with the corresponding DOS singularity locked to the Fermi energy.…”

Section: -2mentioning

confidence: 93%

“…A key point in this scenario is that within the range B c1 < B < B c2 , a repulsive interaction (e.g., Coulomb) is sufficient to induce FC and formation of a flat band with the corresponding DOS singularity locked to the Fermi energy. [16][17][18]39 Now, it is seen from Eq. (5) that finite temperatures, while removing the degeneracy of the FC spectrum, do not change the excess entropy S 0 , threatening the violation of the Nernst theorem.…”

Section: -2mentioning

confidence: 99%

“…We predict that in this region the heat capacity C contains the temperature-independent term C 0 as that of the HF metal YbRh 2 Si 2 does, 40 while jumps of the residual resistivity, represented by ρ c 0 in Sr 3 Ru 2 O 7 , 28 are generated by the second mechanism. 8,39 The coefficients A FC , A LT , and A HF can be extracted from measurements of the resistivity ρ(T ) shown in the left and right panels of Fig. 3.…”

Section: -2mentioning

confidence: 99%

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Quasiclassical physics andT-linear resistivity in both strongly correlated and ordinary metals

2013

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We show that near a quantum-critical point generating quantum criticality of strongly correlated metals where the density of electron states diverges, the quasiclassical physics remains applicable to the description of the resistivity ρ of strongly correlated metals due to the presence of a transverse zero-sound collective mode, reminiscent of the phonon mode in solids. We demonstrate that at T , being in excess of an extremely low Debye temperature T D , the resistivity ρ(T ) changes linearly with T , since the mechanism, forming the T dependence of ρ(T ), is the same as the electron-phonon mechanism that prevails at high temperatures in ordinary metals. Thus, in the region of the T -linear resistivity, electron-phonon scattering leads to near material independence of the lifetime τ of quasiparticles that is expressed as the ratio of the Planck constanth to the Boltzmann constant k B , T τ ∼h/k B . We find that at T < T D there exists a different mechanism, maintaining the T -linear dependence of ρ(T ), and making the constancy of τ fail in spite of the presence of T -linear dependence. Our results are in good agreement with exciting experimental observations. Discoveries of surprising universality in the properties of both strongly correlated metals and ordinary ones provide unique opportunities for checking and expanding our understanding of quantum criticality in strongly correlated compounds. When exploring at different temperatures T a linear in temperature resistivity of these utterly different metals, a universality of their fundamental physical properties has been revealed. 1 On one hand, at low T the linear T -resistivityobserved in many strongly correlated compounds such as high-temperature superconductors and heavy-fermion metals located near their quantum-critical points and therefore exhibiting quantum criticality. Here ρ 0 is the residual resistivity and A is a T -independent coefficient. Explanations based on quantum criticality for the T -linear resistivity have been given in the literature; see, e.g., Refs. 2-5, and references therein. On the other hand, at room temperatures the T -linear resistivity is exhibited by conventional metals such as Al, Ag, or Cu. In the case of a simple metal with a single Fermi surface pocket the resistivity reads e 2 nρ = p F /(τ v F ), 6 where e is the electronic charge, τ is the lifetime, n is the carrier concentration, and p F and v F are the Fermi momentum and the Fermi velocity, correspondingly. Writing the lifetime τ (or inverse scattering rate) of quasiparticles in the form 7,8we obtainwhereh is the Planck constant, k B is the Boltzmann constant, and a 1 and a 2 are T -independent parameters. A challenging point for a theory is that experimental facts corroborate Eq. (3) in the case of both strongly correlated metals and ordinary ones provided that these demonstrate the linear T dependence of their resistivity. 1 Moreover, the analysis of data available in the literature for the most various compounds with the linear dependence of ρ(T ) shows that the coeffi...

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Spin-Lattice Relaxation Rate and Optical Conductivity of Quantum Spin Liquid

Amusia

Shaginyan

2020

Springer Tracts in Modern Physics

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Flat bands and enigma of metamagnetic quantum critical regime in Sr3Ru2O7

Cited by 11 publications

References 52 publications

Magnetic quantum criticality in quasi‐one‐dimensional Heisenberg antiferromagnet

Magnetic quantum criticality in quasi‐one‐dimensional Heisenberg antiferromagnet

Quasiclassical physics andT-linear resistivity in both strongly correlated and ordinary metals

Spin-Lattice Relaxation Rate and Optical Conductivity of Quantum Spin Liquid

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