A Nonmagnetic Impurity in a Quantum Critical Spin System

概要

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A nonmagnetic impurity in a spin gap system is known to induce a local spin-1/2 magnetic moment and gives rise to a Curie-like impurity susceptibility. An impurity in an ordered antiferromagnet on the other hand changes the susceptibility by a finite amount and there is no divergence at low temperatures. Sachdev et al. have, based on analytical calculations, proposed that the susceptibility of an impurity in a quantum critical spin system also shows a Curie law, but with an effective fractional spin different from the spin of the host. Using high temperature series expansions and quantum Monte Carlo simulations we examine the impurity susceptibility in a quantum critical spin-1/2 model. We find that it is very difficult to access any information about the low temperature behaviour of the impurity susceptibility using the high temperature series expansion and compare the results to QMC simulations.
理論物理学刊行会の論文
2002-06-28