Pseudogap suppression by competition with superconductivity in La-based cuprates

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Pseudogap suppression by competition with superconductivity in La-based cuprates

J. Küspert et al.

Phys. Rev. Research 4, 043015 – Published 10 October 2022

Abstract

We carried out a comprehensive high-resolution angle-resolved photoemission spectroscopy (ARPES) study of the pseudogap interplay with superconductivity in La-based cuprates. The three systems ${La}_{2 - x} {Sr}_{x} {CuO}_{4}, {La}_{1.6 - x} {Nd}_{0.4} {Sr}_{x} {CuO}_{4}$ , and ${La}_{1.8 - x} {Eu}_{0.2} {Sr}_{x} {CuO}_{4}$ display slightly different pseudogap critical points in the temperature versus doping phase diagram. We studied the pseudogap evolution into the superconducting state for doping concentrations just below the critical point. In this setting, near optimal doping for superconductivity and in the presence of the weakest possible pseudogap, we uncover how the pseudogap is partially suppressed inside the superconducting state. This conclusion is based on the direct observation of a reduced pseudogap energy scale and re-emergence of spectral weight suppressed by the pseudogap. Altogether these observations suggest that the pseudogap phenomenon in La-based cuprates is in competition with superconductivity for antinodal spectral weight.

Received 27 April 2022
Accepted 30 August 2022

DOI:https://doi.org/10.1103/PhysRevResearch.4.043015

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Electronic structure

Cuprates

Angle-resolved photoemission spectroscopy

Condensed Matter, Materials & Applied Physics

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Vol. 4, Iss. 4 — October - December 2022

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Images

Figure 1
Photoemission intensities recorded on LSCO $p = 0.145$ in the superconducting state. (a) Fermi surface map, recorded with $h ν = 160 eV$ photons at $T = 7 K$ , and integrated $\pm 16 meV$ around the Fermi level. The Brillouin zone boundary is indicated by the dashed grey lines and high symmetry points are labeled $\bar{Γ}, \bar{X}$ , and $\bar{M}$ . Solid black lines indicate nodal and antinodal directions. (b,c) ARPES spectra recorded at $T = 6 K$ along the antinodal ( $\bar{M} \to \bar{X}$ ) and nodal ( $\bar{Γ} \to \bar{X}$ ) directions using $h ν = 55 eV$ photons. (d) Nodal (beige circles) and antinodal (green triangles) symmetrized energy distribution curves (EDCs) at the Fermi momentum, after background subtraction as described in Ref. [20].
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Figure 2
Temperature dependence of nodal and antinodal spectra in Nd-LSCO ( $p = 0.20$ ) and Eu-LSCO ( $p = 0.21$ ) at $h ν = 55 eV$ . (a,b) Energy distribution maps along the antinodal direction (see inset), recorded on Nd-LSCO [21] for temperatures as indicated. (c,d) Corresponding energy distribution curves (EDCs) and symmetrized EDCs at the underlying Fermi momentum. (e) Temperature-dependent nodal and antinodal spectra recorded on Eu-LSCO. Pseudogap temperatures for Nd-LSCO $p = 0.20$ and Eu-LSCO $p = 0.21$ are $T^{*} \approx 80 K$ and $T^{*} \approx 75 K$ [21, 28]. The EDCs in (c)–(e) are normalized to the respective high-energy tail.
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Figure 3
Nodal and antinodal spectra versus temperature in LSCO $p = 0.145$ ( $T_{c} = 37 K$ ) at $h ν = 55 eV$ . (a) Symmetrized antinodal spectra for temperatures as indicated. The pseudogap onset temperature of $T^{*} \approx 162.5$ K, deduced from spectral weight analysis of the EDCs, is consistent with that extracted from transport measurements [28]. (b, c) Comparison of symmetrized antinodal and nodal spectra for $T ≪ T_{c}$ (blue) and $T ≳ T_{c}$ (red). Solid black lines are fits using a phenomenological self-energy function [32] — see text. Vertical dashed lines indicate the peak position. The inset displays a zoom of the low-energy part of the symmetrized EDCs in (b). A background defined using the methodology given in Ref. [20] was subtracted from all spectra.
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Figure 4
Antinodal competition between the pseudogap and superconductivity. (a,b) Integrated spectral weight as a function of temperature. Antinodal weights of LSCO, Eu-LSCO, and Nd-LSCO are plotted with rectangles whereas open circles denote nodal weight. Solid lines are guides to the eye. Vertical dashed lines indicate $T = T^{*}$ and $T_{c} / T^{*}$ , respectively. Error bars provide an estimate of the systematic uncertainty. (c) Antinodal spectral gap as a function of temperature for LSCO (this work) and Nd-LSCO [21]. The gap amplitude follows a linear dependency for $T ≲ T_{c}$ and can be fitted by an order parameter like ${(1 - T / T^{*})}^{0.5}$ behavior for $T ≳ T_{c}$ . The energy resolution defined by the standard deviation of the Fermi step sets the error bars. (d) Phase diagram (temperature versus doping) indicating phase space of different antinodal spectral weight behavior. Outside the pseudogap spectral weight is conserved. We show that there exists a temperature scale $T^{†} < T^{*}$ below which spectral weight is partially recovered.
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