Abstract We studied the magnetic excitations in the quasi-one-dimensional (q-1D) ladder subsystem of Sr 14−x Ca x Cu 24 O 41 (SCCO) using Cu L 3 -edge resonant inelastic X-ray scattering (RIXS). By comparing momentum-resolved RIXS spectra with high ( x = 12.2) and without ( x = 0) Ca content, we track the evolution of the magnetic excitations from collective two-triplon (2 T) excitations ( x = 0) to weakly-dispersive gapped modes at an energy of 280 meV ( x = 12.2). Density matrix renormalization group (DMRG) calculations of the RIXS response in the doped ladders suggest that the flat magnetic dispersion and damped excitation profile observed at x = 12.2 originates from enhanced hole localization. This interpretation is supported by polarization-dependent RIXS measurements, where we disentangle the spin-conserving Δ S = 0 scattering from the predominant Δ S = 1 spin-flip signal in the RIXS spectra. The results show that the low-energy weight in the Δ S = 0 channel is depleted when Sr is replaced by Ca, consistent with a reduced carrier mobility. Our results demonstrate that off-ladder impurities can affect both the low-energy magnetic excitations and superconducting correlations in the CuO 4 plaquettes. Finally, our study characterizes the magnetic and charge fluctuations in the phase from which superconductivity emerges in SCCO at elevated pressures.
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This content will become publicly available on October 1, 2024
Valence transition theory of the pressure-induced dimensionality crossover in superconducting Sr14−xCaxCu24O41
One of the strongest justifications for the continued search for superconductivity within the single-band Hubbard Hamiltonian originates from the apparent success of single-band ladder-based theories in predicting the occurrence of superconductivity in the cuprate coupled-ladder compound Sr{14−x}Ca{x}Cu{24}O{41}. Recent theoretical works have, however, shown the complete absence of quasi-long-range superconducting correlations within the hole-doped multiband ladder Hamiltonian including realistic Coulomb repulsion between holes on oxygen sites and oxygen-oxygen hole hopping. Experimentally, superconductivity in
Sr{14−x}Ca{x}Cu{24}O{41} occurs only under pressure and is preceded by dramatic transition from one to two dimensions that remains not understood. We show that understanding the dimensional crossover requires adopting a valence transition model within which there occurs transition in Cu-ion ionicity from +2 to +1 , with transfer of holes from Cu to O ions [S. Mazumdar, Phys. Rev. B 98, 205153 (2018)]. The driving force behind the valence transition is the closed-shell electron configuration of Cu^{1+}
, a feature shared by cations of all oxides with a negative charge-transfer gap. We make a falsifiable experimental prediction for
Sr{14−x}Ca{x}Cu{24}O{41} and discuss the implications of our results for layered two-dimensional cuprates.
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- Award ID(s):
- 1764152
- NSF-PAR ID:
- 10479066
- Editor(s):
- Stephen E. Nagler
- Publisher / Repository:
- American Physical Society
- Date Published:
- Journal Name:
- Physical Review B
- Edition / Version:
- 1.0
- Volume:
- 108
- Issue:
- 13
- ISSN:
- 2469-9950
- Page Range / eLocation ID:
- 134510
- Subject(s) / Keyword(s):
- ["Ladder Cuprates. Cuprate superconductivity. Three-band Hubbard Model."]
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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