光晶格中的重费米子
Heavy fermions in an optical lattice
摘要：
本文采用平均场论研究了超冷碱土金属原子在近藤格点哈密顿量和抛物禁闭势作用下的二维气体基态性质和输运。在一个均匀系统中，这种平均场论被认为能对重费米子金属和近藤绝缘体给出定性正确的描述：它再现了前者准粒子质量的近藤标度，以及后者激发能隙的相同标度。为了理解陷阱中的基态性质，我们通过局域密度近似扩展了这种平均场论。我们发现，近藤绝缘体间隙表现为壳结构的陷阱密度分布。此外，一个强大的签名的大费米表面预期重费米子系统生存的限制，并可以在飞行时间实验探测。从完全自洽对角化的平均场论，我们能够研究动态的陷阱。我们发现，在重费米液相中的准粒子激发的质量增强表现为减慢的偶极振荡，从陷阱中心的突然位移的结果。
英文摘要：
We employ a mean-field theory to study ground-state properties and transport of a two-dimensional gas of ultracold alklaline-earth metal atoms governed by the Kondo Lattice Hamiltonian plus a parabolic confining potential. In a homogenous system this mean-field theory is believed to give a qualitatively correct description of heavy fermion metals and Kondo insulators: it reproduces the Kondo-like scaling of the quasiparticle mass in the former, and the same scaling of the excitation gap in the latter. In order to understand ground-state properties in a trap we extend this mean-field theory via local-density approximation. We find that the Kondo insulator gap manifests as a shell structure in the trapped density profile. In addition, a strong signature of the large Fermi surface expected for heavy fermion systems survives the confinement, and could be probed in time-of-flight experiments. From a full self-consistent diagonalization of the mean-field theory we are able to study dynamics in the trap. We find that the mass enhancement of quasiparticle excitations in the heavy Fermi liquid phase manifests as slowing of the dipole oscillations that result from a sudden displacement of the trap center.
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