Condensed Matter Physics Seminar

Note Special Time and Place!
11 a.m., Monday, February 20,
Room 2205, Physics Building

 Possible New Physics at Quantum Critical Points: Nontrivial Topology in 2D Antiferromagnets

Zaira Nazario

(Stanford University)

Abstract:  It has recently been proposed that there are degrees of freedom intrinsic to quantum critical points that can contribute to quantum critical physics. We point out that intrinsic critical degrees of freedom exist quite generally below the upper critical dimension. We have recently shown that despite the absence of a Hopf term and zero Berry phase terms, the Neel ordered phase of 2+1 D quantum antiferromagnets have spin 1/2 excitations, i.e. spinons. The spinons are skyrmion excitations of a topological nature. We have recently shown that in 2+1 D antiferromagnets skyrmion excitations are stable at criticality and identify them as the critical excitations. Hence, the critical excitations are fractionalized. Since skyrmion gap is proportional to the spin stiffness, quantum criticality corresponds to skyrmion gap collapse.
Host:  Das Sarma
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