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SUMMARY:The Halon: A Quasiparticle Featuring Critical Charge Fractionalization
DESCRIPTION: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 plus/minus 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 pseudo-spin-1/2 impurity coupled to the quantum-critical environment, in such a way that the rotational symmetry in the pseudo-spin xy-plane is respected, with a small local “magnetic”  field  along the pseudo-spin 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 pseudo-spin 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 prove the existence of halons and quantify their universal features.

LOCATION:Erwin-Schödinger-Saal, IQOQI
DTSTART:20171114T161500
DTEND:20171114T171500
TZID: Europe/Vienna
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