Broun D M, Huttema W A, Turner P J, Ozcan S, Morgan B, Liang Ruixing, Hardy W N, Bonn D A
Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6.
Phys Rev Lett. 2007 Dec 7;99(23):237003. doi: 10.1103/PhysRevLett.99.237003.
The superfluid density rho_{s}(T) identical with1/lambda;{2}(T) has been measured at 2.64 GHz in highly underdoped YBa_{2}Cu_{3}O_{6+y}, at 37 dopings with T_{c} between 3 and 17 K. Within limits set by the transition width DeltaT_{c} approximately 0.4 K, rho_{s}(T) shows no evidence of critical fluctuations as T-->T_{c}, with a mean-field-like transition and no indication of vortex unbinding. Instead, we propose that rho_{s} displays the behavior expected for a quantum phase transition in the (3+1)-dimensional XY universality class, with rho_{s0} proportional, variant(p-p_{c}), T_{c} proportional, variant(p-p_{c});{1/2}, and rho_{s}(T) proportional, variant(T_{c}-T);{1} as T-->T_{c}.
与1/λ²(T)相同的超流密度ρs(T)已在2.64 GHz下于高度欠掺杂的YBa₂Cu₃O₆+y中进行测量，该样品有37种不同的掺杂水平，其临界温度Tc在3 K至17 K之间。在由约0.4 K的转变宽度ΔTc所设定的范围内，当T→Tc时，ρs(T)未显示出临界涨落的迹象，呈现出类似平均场的转变，且没有涡旋解束缚的迹象。相反，我们提出ρs表现出(3 + 1)维XY普适类中量子相变所预期的行为，即当T→Tc时，ρs0 ∝ (p - pc)，Tc ∝ (p - pc)¹/²，且ρs(T) ∝ (Tc - T)¹ 。
