Distinct charge and spin gaps in underdoped<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">YBa</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Cu</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>7</mml:mn><mml:mi>−</mml:mi><mml:mi>δ</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>from analysis of NMR, neutron scattering, tunneling, and quasiparticle relaxation experiments

A systematic quantitative comparison of ``pseudogap'' values obtained from the analysis of charge and spin excitation spectroscopies in underdoped ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ using a temperature-independent gap shows two distinct excitations, one visible in spin-flip spectroscopies like NMR and spin-polarized neutron scattering, and the other in charge excitation spectoscopies like single-particle tunneling and time-resolved quasiparticle relaxation. Both appear to decrease with doping x approximately as $1/x$ and are T independent, existing above and below ${T}_{c}.$ We suggest that the charge excitation can be attributed to a pair-breaking local gap, while the spin excitation can be explained by an intragap local triplet state.

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