Anomalous density fluctuations in a strange metal

Abstract

A central mystery in high-temperature superconductivity is the origin of the so-called strange metal (i.e., the anomalous conductor from which superconductivity emerges at low temperature). Measuring the dynamic charge response of the copper oxides, [Formula: see text], would directly reveal the collective properties of the strange metal, but it has never been possible to measure this quantity with millielectronvolt resolution. Here, we present a measurement of [Formula: see text] for a cuprate, optimally doped BiSrCaCuO ( = 91 K), using momentum-resolved inelastic electron scattering. In the medium energy range 0.1-2 eV relevant to the strange metal, the spectra are dominated by a featureless, temperature- and momentum-independent continuum persisting to the electronvolt energy scale. This continuum displays a simple power-law form, exhibiting behavior at low energy and/ behavior at high energy. Measurements of an overdoped crystal ( = 50 K) showed the emergence of a gap-like feature at low temperature, indicating deviation from power law form outside the strange-metal regime. Our study suggests the strange metal exhibits a new type of charge dynamics in which excitations are local to such a degree that space and time axes are decoupled.

Doping evolution of the charge excitations and electron correlations in electron-doped superconducting La2−xCexCuO4

“…The fitting for x = 0.17 is plotted as the light pink line in Figure 1(c), which agrees with the RIXS measurements quite well. With the fitted p 1 and p 2 , the plasmon energy for x = 0.17 at q = 0 is calculated to be 1.24 eV, which is consistent with infrared optical and EELS measurements [9,29,44].…”

Transverse collective modes in interacting holographic plasmas

“…There we impose Dirichlet boundary conditions on all fields except δA x , on which we instead impose (2.6). As the system is linear, requiring four boundary conditions on a linear combination of four independent solutions can be rephrased as evaluating the determinant of the corresponding matrix of boundary values, and find for what values of (ω, k) that the determinant, δg ty (z) 1 δg xy (z) 1 δΦ y (z) 1 [ ω 2 − k 2 δA x (z) + λ δA x (z)] 1 δg ty (z) 2 δg xy (z) 2 δΦ y (z) 2 [ ω 2 − k 2 δA x (z) + λ δA x (z)] 2 δg ty (z) 3 δg xy (z) 3 δΦ y (z) 3 [ ω 2 − k 2 δA x (z) + λ δA x (z)] 3 δg ty (z) 4 δg xy (z) 4 δΦ y (z) 4 [ ω 2 − k 2 δA x (z) + λ δA x (z)] 4 z→0 = 0 , (A.5)…”

Charge density response and fake plasmons in holographic models with strong translation symmetry breaking

“…It is well-established by now that strongly correlated electron systems, in particular high temperature superconductors and strange metals, display anomalous phenomenology [1]; the charge density response is not an exception. For instance, recent momentum resolved electron energy-loss spectroscopy (M-EELS) experiments found that the spectrum of cuprate strange metals cannot be understood in terms of the conventional physics of a coherent plasmon [2,3]. These unconventional condensed matter systems require unconventional theoretical approaches to describe their phenomenology and the holographic duality provides a suitable framework for this task [4].…”