We provide a general theoretical framework to describe the electromagnetic properties of viscous charged fluids, consisting, for example, electrons in certain solids or plasmas. confirm that finite viscosity leads multiple modes evanescent waves at given frequency, one which is characterized by negative index refraction, as previously discussed simplified model authors. In particular, we explain how optical spectroscopy can be used probe viscosity. concentrate on impact this coefficients...

Kohn's theorem places strong constraints on the cyclotron response of Fermi liquids. Recent observations a doping dependence in mass ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}$ [Legros et al., Phys. Rev. B 106, 195110 (2022)] are therefore surprising because can only be renormalized by large momentum umklapp interactions, which not expected to vary significantly with doping. We show that version continues apply disorder-free non-Fermi-liquids critical boson near...

The critical current density of the Nb3Sn superconductor is strongly dependent on strain applied to material. In order investigate this dependence, it a common practice measure strands for different values axial strain. literature, several models have been proposed describe these experimental data in reversible region. All are capable fitting measurement results region where collected, but tend predict unphysical trends outside range data, and especially large values. paper we present model...

The motion of electrons in the vast majority conductors is diffusive, obeying Ohm’s law. However, recent discovery and growth high-purity materials with extremely long electronic mean free paths has sparked interest non-Ohmic alternatives, including viscous ballistic flow. Although transport regimes have been discovered across a range materials—including two-dimensional electron gases, graphene, topological semimetals, delafossite metals—determining their nature proved to be challenging....

The two-dimensional Yukawa-Sachdev-Ye-Kitaev (2D-YSYK) model provides a universal theory of quantum phase transitions in metals the presence quenched random spatial fluctuations local position critical point. It has Fermi surface coupled to scalar field by spatially Yukawa interactions. We present full numerical solutions self-consistent disorder averaged analysis 2D-YSYK both normal and superconducting states, obtaining electronic spectral functions, frequency-dependent conductivity,...

We revisit the problem of a BCS superconductor in regime where Fermi energy is smaller than Debye energy. This relevant for low-density superconductors such as SrTiO$_3$ that are not BEC limit, well "shape resonances" associated with confinement three-dimensional superconductor. While new, exact results were lacking limit. In two dimensions, we find initial rise pairing temperature $T_c$ at low density $n$ nonanalytic and faster any power $n$. three also nonanalytic, but starts zero slope...

The confinement of a superconductor in thin film changes its Fermi-level density states and is expected to change critical temperature ${T}_{c}$. Previous calculations have reported large discontinuities ${T}_{c}$ when the chemical potential coincides with subband edge. By solving BCS gap equation exactly, we show that such are artifacts continuous function thickness. We also find reduced films compared bulk if lower than value, while for stronger increases decreasing thickness, reaches...

Superconductivity develops in bulk doped ${\mathrm{SrTiO}}_{3}$ and at the ${\mathrm{LaAlO}}_{3}$/${\mathrm{SrTiO}}_{3}$ interface with a dome-shaped density dependence of critical temperature ${T}_{c}$, despite different dimensionalities geometries. We propose that ${T}_{c}$ dome is shape resonance due to quantum confinement superconducting ${\mathrm{SrTiO}}_{3}$. substantiate this interpretation by comparing exact solutions three-dimensional quasi-two-dimensional two-band BCS gap equation....

The concept of Fermi liquid lays a solid cornerstone to the understanding electronic correlations in quantum matter. This ordered many-body state rigorously organizes electrons at zero temperature progressively higher momentum states, up surface. As such, it displays rigidity against perturbations. Such generates Fermi-surface resonances which manifest as longitudinal and transverse collective modes. Although these Fermi-liquid modes have been analyzed observed electrically neutral helium,...

A highlight of Fermi-liquid phenomenology, as explored in neutral [Formula: see text]He, is the observation that collisionless regime shear stress propagates if one dealing with transverse phonon a solid. The existence this "transverse zero sound" requires quasiparticle mass enhancement exceeds critical value. Could such propagating also exist strongly correlated electron systems? Despite some noticeable differences case Galilean continuum, we arrive at verdict sound should be generic for...

The electrodynamic response of ultrapure materials at low temperatures becomes spatially nonlocal. This nonlocality gives rise to phenomena such as hydrodynamic flow in transport and the anomalous skin effect optics. In systems characterized by an anisotropic electronic dispersion, nonlocal dynamics dependent on relative orientation sample with respect applied field, ways that go beyond usual, homogeneous response. Such orientational dependence should manifest itself not only experiments,...

In the framework of EuCARD program, CERN is participating in development a 13 T 100-mm-aperture dipole magnet to upgrade superconducting cable test facility FRESCA at CERN. The conductor candidates for building this are two 1-mm Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands: Powder Tube (PIT) produced by Bruker-EAS and 132/169 RRP Oxford Superconducting Technology (OST). Recently PIT strand has been extensively...

We provide a quantitative and controlled analysis of the phase diagram Yukawa-Sachdev-Ye-Kitaev model on lattice, in normal superconducting states. analyze entire crossover from Bardeen-Cooper-Schrieffer (BCS)/weak coupling to Eliashberg/strong superconductivity, as function fermion-boson interaction strength hopping parameter. Cooper pairs sharp Fermi-liquid quasiparticles at weak evolve into pairing fully incoherent fermions non-Fermi liquid regime. The crossovers leave observable traces...

We discuss various aspects of nonlocal electrical transport in anisotropic metals. For a metal with circular Fermi surface, the scattering rates entering local conductivity and viscosity tensors are well-defined, corresponding to eigenfrequencies linearized collision operator. metals, we provide generalized formulas for these use variational approximation show how they relate microscopic transition probabilities. develop simple model operator arbitrary surface finite number quasi-conserved...

We construct and analyze a lattice generalization of the Yukawa-Sachdev-Ye-Kitaev model, where spinful fermions experience onsite, random, all-to-all interactions with an Einstein bosonic mode, random intersite coherent hopping. obtain exact self-consistent numerical solution model at mean-field level, analytical approximations, for all values fermion-boson coupling hopping, under spin-singlet ansatz particle-hole symmetry, both in normal superconducting states, thus tracing entire phase...

We propose a theory to explain the strain dependence of critical properties in A15 superconductors.Starting from strong-coupling formula for temperature, and assuming that sensitivity stems mostly electron-phonon α 2 F function, we link widening .This is attributed nonlinear generation phonons, which takes place anharmonic deformation potential induced by strain.Based on sum-and difference-frequency wave media, obtain an explicit connection between energy.The resulting model fit experimental...

We provide a quantitative and controlled analysis of the phase diagram Yukawa-SYK model on lattice, in normal superconducting states. analyze entire crossover from BCS/weak-coupling to Eliashberg/strong coupling superconductivity, as function fermion-boson interaction strength hopping parameter. Cooper pairs sharp Fermi-liquid quasiparticles at weak evolve into pairing fully incoherent fermions non-Fermi liquid regime. The crossovers leave observable traces critical temperature,...

We construct and analyze a lattice generalization of the Yukawa-Sachdev-Ye-Kitaev model, where spinful fermions experience on-site, random, all-to-all interactions with an Einstein bosonic mode, random intersite coherent hopping. obtain exact self-consistent numerical solution model at mean-field level, analytical approximations, for all values fermion-boson coupling hopping, under spin-singlet ansatz particle-hole symmetry, both in normal superconducting states, thus tracing entire phase...

We determine the global renormalization group (RG) flow of Sachdev-Ye-Kitaev (SYK) model. From a controlled truncation infinite hierarchy exact functional RG equations, we identify several fixed points. Apart from stable point, associated with celebrated non-Fermi liquid state model, find another point related to an integer-valence state. These points are separated by discontinuity one relevant direction, describing quantum first-order transition. Most notably, fermionic spectrum continues...

The motion of electrons in the vast majority conductors is diffusive, obeying Ohm's law. However, recent discovery and growth high-purity materials with extremely long electronic mean free paths has sparked interest non-ohmic alternatives, including viscous ballistic flow. Although transport regimes have been discovered across a range materials, two-dimensional electron gases, graphene, topological semimetals, delafossite metals, determining their nature proved to be challenging. Here, we...

Kohn's theorem places strong constraints on the cyclotron response of Fermi liquids. Recent observations a doping dependence in mass La$_{2-x}$Sr$_x$CuO$_4$ (Legros et al., Phys. Rev. B 106, 195110 (2022)) are therefore surprising because can only be renormalized by large momentum umklapp interactions which not expected to vary significantly with doping. We show that version continues apply disorder-free non-Fermi liquids critical boson near zero momentum. However, marginal arising from...

The two-dimensional Yukawa-Sachdev-Ye-Kitaev (YSYK) model provides a universal theory of quantum phase transitions in metals the presence quenched random spatial fluctuations local position critical point. It has Fermi surface coupled to scalar field by spatially Yukawa interactions. We present full numerical solutions self-consistent disorder averaged analysis YSYK both normal and superconducting states, obtaining electronic spectral functions, frequency-dependent conductivity, superfluid...

The pairing temperature of superconducting thin films is expected to display, within the Bardeen-Cooper-Schrieffer theory, oscillations as a function film thickness. We show that pattern these switches between two different periodicities at density-dependent value coupling. transition most abrupt in anti-adiabatic regime, where Fermi energy less than Debye energy. To support our numerical data, we provide new analytical expressions for chemical potential and thickness, which only differ from...

Quantum confinement in a thin-film geometry offers viable routes for tuning the critical properties of superconductors through modification both density states and pairing interaction. Low-density systems like doped strontium titanate are especially susceptible to these confinement-induced effects. In this paper, we show that superconducting temperature $T_c$ is enhanced quantum SrTiO$_3$/SrTi$_{1-x}$Nb$_x$O$_3$/SrTiO$_3$ heterostructures at $x=1\%$ concentration, by measuring resistivity...