Science Advances

Supplementary Materials

This PDF file includes:

  • Materials and Methods
  • Table S1. Refined parameters for the fcc RbCs2C60 (sample II) phase space group Fm 3 m, phase fraction refined to 98.994(2)% obtained from the Rietveld analysis of the SXRPD data collected at 10 and 300 K (λ = 0.40006 Å).
  • Table S2. Refined parameters for the fcc Rb0.5CsC60 (sample I) phase space group Fm 3 m, phase fraction refined to 83.23(3)% obtained from the Rietveld analysis of the SXRPD data collected at 5 and 300 K (λ = 0.39989 Å).
  • Table S3. Structural parameters for the fcc RbCsC60 phase space group Fm 3 m, phase fraction refined to 82.05(4)% at 0.41 GPa obtained from the Rietveld analysis of the SXRPD data collected at 0.41 and 7.82 GPa, at 7 K (λ = 0.41305 Å).
  • Table S4. 13C spin-lattice relaxation rates, 1/13T1, in RbxCs3−xC60 (0 ≤ x ≤ 3) at 300 K, calculated interfulleride exchange constants, J, and 13C spin-lattice relaxation rates divided by temperature at 35 K just above the superconducting transition temperatures.
  • Fig. S1. Temperature dependence of the ZFC and FC magnetization, M (20 Oe) for the RbxCs3−xC60 (0.35 ≤ x ≤ 2) compositions.
  • Fig. S2. Temperature dependence of the magnetization, M (20 Oe, ZFC protocol) for the RbxCs3−xC60 (0.35 ≤ x ≤ 2) compositions at selected pressures.
  • Fig. S3. Low-temperature, high-pressure SXRPD.
  • Fig. S4. Pressure dependence of the low-temperature unit cell volume of the RbxCs3−xC60 (0.35 ≤ x ≤ 2) phases (x = 0.35, 1.5, and 2 at 7 K; x = 0.5 and 1 at 20 K).
  • Fig. S5. Temperature evolution of the volume, V, occupied per fulleride anion for the RbxCs3−xC60 (x = 1.5, 2) compositions over the full temperature range of the present diffraction experiments.
  • Fig. S6. Final observed (red circles) and calculated (blue line) SXRPD profiles for the RbCsC60 (A, λ = 0.39989 Å) and RbCs2C60 (B, λ = 0.40006 Å) samples at 5 and 10 K, respectively.
  • Fig. S7. Temperature dependence of the square root of the second moment, (13M2)1/2, of the 13C NMR spectra of the RbxCs3−xC60 (0.35 ≤ x ≤ 3) compositions.
  • Fig. S8. Temperature dependence of the (A) 87Rb and (B) 133Cs T-site spin-lattice relaxation rates divided by temperature, 1/87T1T and 1/133T1T, respectively, for the RbxCs3−xC60 (0 ≤ x ≤ 3) compositions.
  • Fig. S9. Temperature dependence of the 13C spin-lattice relaxation rates divided by temperature, 1/13T1T, for Rb2CsC60 and Rb3C60.
  • Fig. S10. Temperature dependence of the stretch exponent, a, for the (A) 13C and (B) 133Cs magnetization recoveries in the RbxCs3−xC60 compositions.
  • Fig. S11. Temperature dependence of the IR active T1u(4) C60 3– vibrational mode for the RbxCs3−xC60 (0 ≤ x ≤ 3) compositions.
  • Fig. S12. Representative IR spectra for the RbxCs3−xC60 (0 ≤ x ≤ 3) compositions at selected temperatures illustrating the IR spectroscopic signatures of the various electronic states encountered.
  • Fig. S13. Representative peak fits in the spectral region of the T1u(4) vibrational mode at selected temperatures for RbCsC60 (A) and RbCs2C60 (B).
  • Fig. S14. Temperature dependence of the 13C (A) and the T-site 133Cs (B) spinl-attice relaxation rate, 1/T1, normalized to its value at Tc for the RbxCs3−xC60 (0.35 ≤ x ≤ 3) compositions.
  • Fig. S15. (Main panels) Temperature dependence of the electronic part of the zero-field specific heat divided by temperature, (C − Cn)/T, obtained after subtracting the background phonon contribution from the total specific heat in
    RbxCs3−xC60 (0.35 ≤ x ≤ 3), K3C60, and Na2CsC60.
  • Fig. S16. Temperature dependence of the specific heat C divided by temperature T, C/T, for RbxCs3−xC60 (0.35 ≤ x ≤ 3) and K3C60.

Download PDF

Files in this Data Supplement: