Quasiparticle interference and the interplay between superconductivity and density wave order in the cuprates

Benjamin

et al. 2016

Phys. Rev. B

When immersed in a see of electrons, local impurities give rise to density modulations known as Friedel oscillations. In spite of the generality of this phenomenon, the exact shape of these modulations is usually computed only for non-interacting electrons with a quadratic dispersion relation. In actual materials, Friedel oscillations are a viable way to access the properties of electronic quasiparticles, including their dispersion relation, lifetime, and pairing. In this work we analyze the signatures of Friedel oscillations in STM and X-ray scattering experiments, focusing on the concrete example of cuprates superconductors. We identify signatures of Friedel oscillations seeded by impurities and vortexes, and explain experimental observations that have been previously attributed to a competing charge order. Contents

Section: B Stm: Dispersive Vs Non-dispersive Peakssupporting

confidence: 74%

Friedel oscillations as a probe of fermionic quasiparticles

Benjamin

et al. 2016

Phys. Rev. B

“…Specifically, our theory explains why (i) the x-ray-scattering signal is peaked at wave vector (q, 0), rather than at (q, q), as expected for CDWs; (ii) the RIXS signal is peaked at frequency = 0 and is accompanied by weaker dispersive inelastic peaks. Our findings also agree with earlier STS experiments of BSCCO [8][9][10], which found that the incommensurate checkerboard order has a dominant PDW character [72][73][74][75]. Attributing the x-ray signal to fluctuations of the pairing order parameter (PDW) explains its temperature dependence: these fluctuations are strongest at the critical temperature of superconducting order parameter, T c , in agreement with the experimental observations ( [12,16]).…”

supporting

confidence: 92%

“…Specifically, our theory explains why the experimental signal is peaked at (q, 0), rather than at (q, q), as expected for CDWs. Our findings also agree with earlier STS experiments of BSCCO [8][9][10], which found that the incommensurate checkerboard order has a dominant PDW character [68][69][70][71]. The proposed PDW scenario explains why the signal detected in X-ray scattering of cuprates is orders of magnitude smaller than the one observed in ordinary CDW materials (δn δ∆).…”

supporting

confidence: 92%

Minimal model of charge and pairing density waves in x-ray scattering experiments

Dentelski

2020

Phys. Rev. Research

Competing density waves play an important role in the mystery of high-temperature cuprate superconductors. In spite of the large amount of experimental evidence, the fundamental question of whether these modulations represent charge or pairing density waves (CDWs or PDWs) is still debated. Here we present a method to answer this question using both momentum and energy-resolved resonant x-ray-scattering maps. Starting from a minimal model of density waves in superconductors, we identify distinctive signatures of incipient CDWs and PDWs. The generality of our approach is confirmed by a self-consistent solution of an extended Hubbard model with attractive interaction. By considering the available experimental data, we claim that the spatial modulations in cuprates have a predominant PDW character. Our work paves the way for using x ray to identify competing and intertwined orders in superconducting materials.

“…Im [ ( , )]. In the presence of weak time-independent scatterers its Fourier transform is given by [18,[37][38][39][40][41]…”

Section: Stm: Theory and Experimentsmentioning

confidence: 99%

Exploring quasiparticles in high-T_ccuprates through photoemission, tunneling, and x-ray scattering experiments

Benjamin

et al. 2015

New J. Phys.

One of the key challenges in the field of high-temperature superconductivity is understanding the nature of fermionic quasiparticles. Experiments consistently demonstrate the existence of a second energy scale, distinct from the d-wave superconducting gap, that persists above the transition temperature into the 'pseudogap' phase. One common class of models relates this energy scale to the quasiparticle gap due to a competing order, such as the incommensurate 'checkerboard' order observed in scanning tunneling microscopy (STM) and resonant elastic x-ray scattering (REXS). We develop a minimal phenomenological model that allows us to quantitatively describe STM and REXS experiments and discuss their relation with photoemission spectroscopy. Experimental signatures of the incommensurate order are explained in terms of scattering of short-lived quasiparticles from local impurities. We identify the unknown second energy scale with the inverse lifetime of the quasiparticles, refocusing questions about the nature of the pseudogap phase to the study of the origin of inelastic scattering.