Seminar by Yuan Wan (Perimeter Institute) "Spinon walk in quantum spin ice"

Seminar:

• Date: July 14th (Thu)
• Time: 11:00-12:00
• Venue: D014, Lab1
• Speaker: Yuan Wan, Postdoctoral Researcher, Perimeter Institute for Theoretical Physics  

“Spinon walk in quantum spin ice”

Spin ice is a frustrated magnet that displays rich emergent phenomena.

For example, the magnetic moments carried by the spins may separate into mobile magnetic charges, giving rise to a novel fractional excitation known as the monopole. In the classical spin ice, the monopoles diffuse by virtue of thermal fluctuations. Their diffusion produces the unique dynamic properties of the classical spin ice.

Quantum spin ice is a novel family of spin ice magnets that possess substantial quantum fluctuations. The fractional excitations are spinons, which are quantum analog of the monopoles in classical spin ice. As opposed to a diffusing monopole, the spinon propagates via quantum tunnelling. Yet, different from a conventional quantum particle, the spinon moves in a background of disordered spins. The orientation of background spins controls the spinon motion, whereas the spinon motion in turn alters the spin background. We may ask what a suitable framework for understanding the spinon dynamics is and furthermore, whether there is a simple picture for the spinon propagation in quantum spin ice.

In this talk, I will present our recent study on a minimal model that captures the essential features of single spinon dynamics in quantum spin ice. I will demonstrate that the spinon motion can be thought of as a random walk with entropy-induced memory in imaginary time. Our numerical simulation shows that the spinon dynamics exhibits a remarkable renormalization phenomenon where the spinon propagates as a massive, nearly free quantum particle at low energy despite its strong coupling to a disordered spin background at the lattice scale. I will also briefly touch upon the implications of our findings.

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Contact: shiho.saito@oist.jp