Analogies of phonon anomalies and electronic gap features in the infrared response of Sr14-xCaxCu24O41and underdoped YBa2Cu3O6+x

Petr Adamus; Bing Xu; Premysl Marsik; Adam Dubroka; Paulína Barabasová; Hana Růžičková; Pascal Puphal; Ekaterina Pomjakushina; Jeffery L Tallon; Yves-Laurent Mathis; Dominik Munzar; Christian Bernhard

doi:10.1088/1361-6633/acbe4f

Analogies of phonon anomalies and electronic gap features in the infrared response of Sr14-xCa_xCu₂₄O₄₁and underdoped YBa₂Cu₃O6+x

Rep Prog Phys. 2023 Mar 10;86(4). doi: 10.1088/1361-6633/acbe4f.

Authors

Affiliations

¹ Department of Condensed Matter Physics, Faculty of Science, Masaryk University, Kotlářská 2, 61137 Brno, Czech Republic.
² University of Fribourg, Department of Physics, Chemin du Musée 3, CH-1700 Fribourg, Switzerland.
³ Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
⁴ Laboratory for Multiscale Materials Experiments, PSI, 5232 Villigen, Switzerland.
⁵ Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany.
⁶ Victoria University of Wellington, Robinson Research Institute, POB 33436, Lower Hutt 5046, New Zealand.
⁷ Karlsruhe Institute of Technology, Institute for Beam Physics and Technology, Hermann-von-Helmhotz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany.

PMID: 36821858
DOI: 10.1088/1361-6633/acbe4f

Abstract

We present an experimental and theoretical study which compares the phonon anomalies and the electronic gap features in the infrared response of the weakly coupled two-leg-ladders in Sr14-xCa_xCu₂₄O₄₁(SCCO) with those of the underdoped high-T_csuperconductor YBa₂Cu₃O6+x(YBCO) and thereby reveals some surprising analogies. Specifically, we present a phenomenological model that describes the anomalous doping- and temperature-dependence of some of the phonon features in thea-axis response (field along the rungs of the ladders) of SCCO. It assumes that the phonons are coupled to charge oscillations within the ladders. Their changes with decreasing temperature reveal the formation of a crystal (density wave) of hole pairs that are oriented along the rungs. We also discuss the analogy to a similar model that was previously used to explain the phonon anomalies and an electronic plasma mode in thec-axis response (field perpendicular to the CuO₂planes) of YBCO. We further confirm that an insulator-like pseudogap develops in thea-axis conductivity of SCCO which closely resembles that in thec-axis conductivity of YBCO. Most surprisingly, we find that thec-axis conductivity (field along the legs of the ladders) of SCCO is strikingly similar to the in-plane one (field parallel to the CuO₂planes) of YBCO. Notably, in both cases a dip feature develops in the normal state spectra that is connected with a spectral weight shift toward low frequencies and can thus be associated with precursor superconducting pairing correlations that are lacking macroscopic phase coherence. This SCCO-YBCO analogy indicates that collective degrees of freedom contribute to the low-energy response of underdoped highT_ccuprates and it even suggests that the charges in the CuO₂planes tend to segregate forming quasi-one-dimensional structures similar to the two-leg ladders, as predicted for the stripe-scenario or certain intertwinned states.

Keywords: high-Tc cuprates; infrared spectroscopy; strongly correlated electron systems.

Publication types

Review