Searcharxiv⌕ Search

arXiv subjects

M. V. Zverev

Publications and source records attributed to M. V. Zverev.

At least 19 recordsLinked to original sources
arXiv2024

A unified quasiparticle approach to the theory of strongly correlated electron liquids

Landau's quasiparticle formalism is generalized to describe a wide class of strongly correlated Fermi systems, in addition to conventional Fermi liquids. This class includes (i) so-called marginal exemplars and (ii) systems that harbor interaction-driven flat bands, in both of which manifestations of non-Fermi-liquid behavior are well documented. Specifically, the advent of such flat bands is attributed to a spontaneous topological rearrangement of the Landau state that supplements the conventional Landau quasiparticle picture with a different set of quasiparticles, the so-called fermion condensate, whose single-particle spectrum is dispersionless. The celebrated Landau-Luttinger theorem is extended to marginal Fermi liquids, in which the density of the augmented quasiparticle system is shown to coincide with the particle density. On the other hand, the total density of a system hosting an interaction-driven flat band turns out to be the sum of the densities of the two quasiparticle subsystems: the Landau-like component and the fermion condensate. We demonstrate that within the framework of the scenario proposed, a long-standing problem faced by theories of $D$-wave superconductivity in cuprates, namely a consistent explanation of the so-called Uemera plot, can be naturally resolved.

cond-mat.str-el↗
arXiv2023

Transport properties of strongly correlated Fermi systems

In our short review, we consider the transport properties of strongly correlated Fermi systems like heavy fermion metals and high-$T_c$ superconductors. Their transport properties are defined by strong inter-particle interaction forming flat bands in these compounds. Indeed, in contrast to the behavior of the transport properties of conventional metals, the strongly correlated compounds exhibit the linear in temperature resistivity, $ρ(T)\propto T$. We analyze the magnetoresistance and show that it under the application of magnetic field becomes negative. It is shown that near a quantum phase transition, when the density of electronic states diverges, semiclassical physics remains applicable to describe the resistivity $ρ$ of strongly correlated metals due to the presence of a transverse zero-sound collective mode, representing the phonon mode in solids. We demonstrate that when $T$ exceeds the extremely low Debye temperature $T_D$, the resistivity $ρ(T)$ changes linearly with $T$, since the mechanism of formation of the $T$-dependence $ρ(T)$ is similar electron-phonon mechanism, which predominates at high temperatures in ordinary metals. Thus, in the region of $T$-linear resistance, electron-phonon scattering leads to a lifetime of $τ$ quasiparticles practically independent of the material, which is expressed as the ratio of the Planck constant $\hbar$ to the Boltzmann constant constant $k_B$, $Tτ\sim \hbar/k_B$. We explain that due to the non-Fermi-liquid behavior the real part of the frequency-dependent optical conductivity $σ^R_{opt}(ω)$ exhibits a scaling behavior, and demonstrates the unusual power law behavior $σ^R_{opt}(ω)\proptoω^{-1}$, rather than the well-known one shown by conventional metals, $σ^R_{opt}(ω)\proptoω^{-2}$.

cond-mat.str-el↗
arXiv2023

Quantum Phase Transition in $\rm CeCoIn_5$: Experimental Facts and Theory

Condensed-matter community is involved in hot debate on the nature of quantum critical points (QCP) governing the low-temperature properties of heavy fermion metals. The smeared jump like behavior revealed both in the residual resistivity $ρ_0$ and the Hall resistivity $R_H$, along with the violation of the time invariance symmetry $\mathcal{T}$ and the charge invariance $\mathcal{C}$, including the violation of quasiparticle-hole symmetry, and providing vital clues on the origin of both the non-Fermi-liquid behavior and QCP. For the first time, based on a number of important experimental data, we show that these experimental observations point out unambiguously that QCP of $\rm CeCoIn_5$ is accompanied by the symmetry violation, and QCP itself is represented by the topological fermion-condensation quantum phase transition (FCQPT) connecting two Fermi surfaces of different topological charges.

cond-mat.str-el↗
arXiv2022

Comment on "Stranger than metals"

P. W. Phillips, N. E. Hussey, P. Abbamonte (Review Article, 8 July 2022, eabh4273) consider heavy fermion (HF) metals and high-$T_c$ superconductors naming them strange metals. They analyze such features of strange metals as quantum criticality, Planckian dissipation and recently observed fundamental link between the high-$T_c$ superconductivity and strange metals, and conclude that these problems can be possibly resolved within the framework of theories based on gravity, etc. In this comment we discuss that this claim is not correct and the successful description of the quantum criticality, Planckian dissipation and recently observed fundamental link between the high-$T_c$ superconductivity and strange metals has been given within the framework of the fermion condensation theory.

cond-mat.str-el↗
arXiv2021

Quasiparticle Pattern of Phenomena in Exotic Superconductors

The quasiparticle formalism invented by Lev Landau for description of conventional Fermi liquids is generalized to exotic superconductivity attributed to Cooper pairing, whose measured properties defy explanation within the standard BCS-Fermi Liquid description. We demonstrate that in such systems the quasiparticle number remains equal to particle number, just as in common Fermi liquids. We are then able to explain the puzzling relationship between the variation with doping $x$ of two key properties of the family La$_{2-x}$Sr$_x$Cu0$_4$ of exotic superconductors, namely the $T=0$ superfluid density $ρ_{s0}(x)$ and the coefficient $A_1(x)$ in the linear-in-$T$ component of the normal-state low-$T$ resistivity $ρ(T)=ρ_0+A_1T+A_2T^2$, in terms of the presence of interaction-induced flat bands in the ground states of these metals.

cond-mat.str-el↗
arXiv2020

Topological disorder triggered by interaction-induced flattening of electron spectra in solids

We address the intervention of classical-like behavior, well documented in experimental studies of strongly correlated electron systems of solids that emerges at temperatures $T$ far below the Debye temperature $T_D$. We attribute this unexpected phenomenon to spontaneous rearrangement of the conventional Landau state beyond a critical point at which the topological stability of this state breaks down, leading to the formation of an interaction-induced flat band adjacent to the nominal Fermi surface. We demonstrate that beyond the critical point, the quasiparticle picture of such correlated Fermi systems still holds, since the damping of single-particle excitations remains small compared with the Fermi energy $T_F=p^2_F/2m_e$. A Pitaevskii-style equation for determination of the rearranged quasiparticle momentum distribution $n_*({\bf p})$ is derived, which applies to explanation of the linear-in-$T$ behavior of the resistivity $ρ(T)$ found experimentally.

cond-mat.str-el↗
arXiv2019

Impact of $e-e$ interactions on the superfluid density of dirty superconductors

Landau's theory of the Fermi liquid is adapted to analyze the impact of electron-electron ($e-e$) interactions on the deficit of the superfluid density $ρ_{s0}=ρ_s(T=0)$ in dirty superconducting electron systems in which the damping $γ$ of single-particle excitations exceeds the zero temperature BCS gap $Δ_0$. In the dirty strong-coupling limit $γ/Δ_0\gg 1,m^*/m_e\gg 1$, the formula derived for $ρ_{s0}$ is shown to coincide with the well-known empirical Uemura relation provided pair-breaking contributions are nonexistent. The roles of the crystal lattice and magnetic pair-breaking effects in the observed decline of the zero-temperature superfluid density $ρ_{s0}$ in overdoped LSCO compounds are also discussed. Our method is also applied to elucidation of results from the pioneering experimental studies performed recently by Bozovic and collaborators in overdoped LSCO compounds.

cond-mat.str-el↗
arXiv2018

Toward a topological scenario for high-temperature superconductivity of copper oxides

The structure of the joint phase diagram demonstrating high-$T_c$ superconductivity of copper oxides is studied on the basis of the theory of interaction-induced flat bands. Prerequisites of an associated topological rearrangement of the Landau state are established, and related non-Fermi-liquid (NFL) behavior of the normal states of cuprates is investigated. We focus on manifestations of this behavior in the electrical resistivity $ρ(T)$, especially the observed gradual crossover from normal-state $T$-linear behavior $ρ(T,x)=A_1(x)T$ at doping $x$ below the critical value $x_c^h$ for termination of superconductivity, to $T$-quadratic behavior at $x>x_c^h$, which is incompatible with predictions of the conventional quantum-critical-point scenario. It is demonstrated that at $x<x^h_c$, in agreement with available experimental data, the coefficient $A_1( x)$ is decomposed into the product of two factors, one of which changes linearly with doping $x$, while the second is universal, being of the Planckian form.

cond-mat.str-el↗
arXiv2017

Interplay between BCS and Mott physics in the phenomenon of high-$T_c$ superconductivity

Superconducting electron systems of solids hosting flat bands are studied, with a view to improved understanding of the fundamental physics giving rise to high-temperature superconductivity. We present a modified form of the set of Gor'kov equations of BCS theory that incorporates a Mott-like gap in the single-particle spectrum. Such a quantity is emergent in systems with flat bands having interactions repulsive in the Cooper channel, provided particle-hole symmetry is broken. The equations so obtained are applied to the elucidation of features of the two-gap structure of single-particle spectra of underdoped high-$T_c$ superconductors, as revealed in angle-resolved photoemission spectrometry.

cond-mat.str-el↗
arXiv2016

Topological basis for understanding the behavior of the heavy-fermion metal $\rm {β-YbAlB_4}$ under application of magnetic field and pressure

Informative recent measurements on the heavy-fermion metal $\rm β-YbAlB_4$ performed with applied magnetic field and pressure as control parameters are analyzed with the goal of establishing a sound theoretical explanation for the inferred scaling laws and non-Fermi-liquid (NFL) behavior, which demonstrate some unexpected features. Most notably, the robustness of the NFL behavior of the thermodynamic properties and of the anomalous $T^{3/2}$ temperature dependence of the electrical resistivity under applied pressure $P$ in zero magnetic field $B$ is at variance with the fragility of the NFL phase under application of a field. We show that a consistent topological basis for this combination of observations, as well as the empirical scaling laws, may be found within fermion-condensation theory in the emergence and destruction of a flat band, and explain that the paramagnetic NFL phase takes place without magnetic criticality, thus not from quantum critical fluctuations. Schematic $T-B$ and $T-P$ phase diagrams are presented to illuminate this scenario.

cond-mat.str-el↗
arXiv2015

Fate of the Wiedemann-Franz law near quantum critical points of electron systems in solids

We introduce and analyze two different scenarios for violation of the Wiedemann-Franz law in strongly correlated electron systems of solids, close to a topological quantum critical point (TQCP) where the density of states $N(0)$ diverges. The first, applicable to the Fermi-liquid (FL) side of the TQCP, involves a transverse zero-sound collective mode that opens a new channel for the thermal conductivity, thereby enhancing the Lorenz number $L(0)$ relative to the value $L_0=π^2k^2_B/3e^2$ dictated by conventional FL theory. The second mechanism for violation of the WF law, relevant to the non-Fermi-liquid (NFL) side of the TQCP, involves the formation of a flat band and leads instead to a reduction of the Lorenz number.

cond-mat.str-el↗
arXiv2015

Interaction-induced merging of Landau levels in an electron system of double quantum wells

We show that the disappearance of the chemical potential jumps over the range of perpendicular magnetic fields at fixed integer filling factor in a double quantum well with a tunnel barrier is caused by the interaction-induced level merging. The distribution function in the merging regime is special in that the probability to find an electron with energy equal to the chemical potential is different for the two merged levels.

cond-mat.str-el↗
arXiv2015

High-$T_c$ superconductivity of electron systems with flat bands pinned to the Fermi surface

The phenomenon of flat bands pinned to the Fermi surface is analyzed on the basis of the Landau-Pitaevskii relation, which is applicable to electron systems of solids. It is shown that the gross properties of normal states of high-$T_c$ superconductors, frequently called strange metals, are adequately explained within the flat-band scenario. Most notably, we demonstrate that in electron systems moving in a two-dimensional Brillouin zone, superconductivity may exist in domains of the Lifshitz phase diagram lying far from lines of critical antiferromagnetic fluctuations, even if the effective electron-electron interaction in the Cooper channel is repulsive.

cond-mat.supr-con↗
arXiv2014

Comment on "Topological excitations and the dynamic structure factor of spin liquids on the kagome lattice" (Punk, M., Chowdhury, D. & Sachdev, S. Nature Physics 10, 289-293 (2014))

The authors of a recent paper evidently take the view that the whole of progress made toward a theoretical understanding of the physics of quantum spin liquids (QSL) is associated with models of the kind proposed and applied in their present work. As motivation for this work, they observe that in contrast to existing theoretical models of both gapped and gapless spin liquids, which give rise to sharp dispersive features in the dynamic structure factor, the measured dynamic structure factor reveals an excitation continuum that is remarkably flat as a function of frequency. They go on to assert that "so far, the only theoretical model for a spin liquid state on the kagome lattice which naturally gives rise to a flat excitation band at low energies consists of the $Z_2$ spin liquids". Here we point out that there already exists a different and demonstrably successful approach to the QSL problem that does naturally feature a flat band.

cond-mat.str-el↗
arXiv2013

Conventional BCS, Unconventional BCS, and Non-BCS Hidden Dineutron Phases in Neutron Matter

The nature of pairing correlations in neutron matter is re-examined. Working within the conventional approximation in which the $nn$ pairing interaction is provided by a realistic bare $nn$ potential fitted to scattering data, it is demonstrated that the standard BCS theory fails in regions of neutron number density where the pairing constant $λ$, depending crucially on density, has a non-BCS negative sign. We are led to propose a non-BCS scenario for pairing phenomena in neutron matter that involves the formation of a hidden dineutron state. In low-density neutron matter where the pairing constant has the standard BCS sign, two phases organized by pairing correlations are possible and compete energetically: a conventional BCS phase and a dineutron phase. In dense neutron matter, where $λ$ changes sign, only the dineutron phase survives and exists until the critical density for termination of pairing correlations is reached at approximately twice the neutron density in heavy atomic nuclei.

nucl-th↗
arXiv2013

Flat Bands and Enigma of Metamagnetic Quantum Critical Regime in Sr3Ru2O7

Understanding the nature of field-tuned metamagnetic quantum criticality in the ruthenate Sr3Ru2O7 has presented a significant challenge within condensed matter physics. It is known from experiments that the entropy within the ordered phase forms a peak, and is unexpectedly higher than that outside, while the magnetoresistivity experiences steep jumps near the ordered phase. We find a challenging connection between Sr3Ru2O7 and heavy-fermion metals expressing universal physics that transcends microscopic details. Our construction of the T-B phase diagram of Sr3Ru2O7 permits us to explain main features of the experimental one, and unambiguously implies an interpretation of its extraordinary low-temperature thermodynamic in terms of fermion condensation quantum phase transition leading to the formation of a flat band at the restricted range of magnetic fields B. We show that it is the flat band that generates both the entropy peak and the resistivity jumps at the QCPs.

cond-mat.str-el↗
arXiv2012

Different scenarios of topological phase transitions in homogeneous neutron matter

We study different scenarios of topological phase transitions in the vicinity of the π^0 condensation point in neutron matter. The transitions occur between the Fermi-liquid state and a topologically different one with two sheets of the Fermi surface. Two possibilities of a rearrangement of quasiparticle degrees of freedom are shown: the first-order topological phase transition and the second-order one. The order of the phase transition is found to be strongly dependent on the value of the critical wave vector of the soft π^0 mode. The thermodynamics of the system is also studied. It is shown that the topology of the quasiparticle momentum distribution is mainly determined by the neutron matter density, while the temperature T is essential in a narrow density region. A simple explanation of the first-order topological phase transition at T=0 is given.

nucl-th↗