Low-temperature studies of the NMR frequency shift in superfluid <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mmultiscripts><mrow><mi mathvariant="italic">A</mi></mrow><mprescripts></mprescripts><mrow></mrow><mrow><mn>3</mn></mrow><mrow></mrow><mrow></mrow></mmultiscripts></mrow></math></span>

P. Schiffer; M. T. O’Keefe; Hiroshi Fukuyama; D. D. Osheroff

doi:10.1103/PhysRevLett.69.3096

Low-temperature studies of the NMR frequency shift in superfluid ${}^{3}A$

P. Schiffer, M. T. O’Keefe, Hiroshi Fukuyama, and D. D. Osheroff

Phys. Rev. Lett. 69, 3096 – Published 23 November 1992

Abstract

We report the first measurements of the longitudinal resonance frequency [ $ν_{long}$ (A)] in ${}^{3}A$ in the low-temperature limit, as well as new measurements near $T_{c}$ . In the low-temperature limit, our data agree well with theoretically predicted behavior. The data allow us to make the first estimates of the BCS cutoff energy as a function of pressure and of the zero-temperature A-phase energy gap.