Halon: A quasiparticle featuring critical charge fractionalization

Article

关键词: INSULATOR TRANSITION;    QUANTUM IMPURITY;    ANTIFERROMAGNET;    FIELD;    SPIN;   

DOI  :  10.1103/PhysRevB.98.214516

来源: SCIE

【 摘 要 】

The halon is a special critical state of an impurity in a quantum-critical environment. The hallmark of the halon physics is that a well-defined integer charge gets fractionalized into two parts: a microscopic core with half-integer charge and a critically large halo carrying a complementary charge of +/- 1/2. The halon phenomenon emerges when the impurity-environment interaction is fine-tuned to the vicinity of a boundary quantum critical point (BQCP), at which the energies of two quasiparticle states with adjacent integer charges approach each other. The universality class of such BQCP is captured by a model of pseudospin-1/2 impurity coupled to the quantum-critical environment, in such a way that the rotational symmetry in the pseudospin xy plane is respected, with a small local magnetic field along the pseudospin z axis playing the role of control parameter driving the system away from the BQCP. On the approach to BQCP, the half-integer projection of the pseudospin on its z axis gets delocalized into a halo of critically divergent radius, capturing the essence of the phenomenon of charge fractionalization. With large-scale Monte Carlo simulations, we confirm the existence of halons-and quantify their universal features-in O(2) and O(3) quantum critical systems.

【 授权许可】

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