SWC Seminar - Nature of Quantum Spin Liquid in Kagome Heisenberg Antiferromagnet: Dynamics and Entanglement Response | Shull Wollan Center

ABSTRACT

Quantum spin liquids (QSL) are materials that do not order magnetically down to the lowest temperatures and host exotic excitations. The S = 1/2 Heisenberg antiferromagnet model on the kagome lattice (KAFM) constitutes one of the most promising platforms for QSL due to its geometric frustration. Experiments on the kagome compound herberthsmithite show that it is a QSL, but its nature remains under debate. 

In the first part of this talk,  we present dynamical spin structure factors for competing phases in KAFM.  By comparison with the well-defined magnetic order and chiral QSL sitting nearby in the global phase diagram, the KAFM with nearest-neighbor interactions shows distinct dynamical response behaviors. First of all, a wide spectral distribution in the energy scans of dynamical spin structure factor reveals an excitation continuum forming in high frequency, indicating QSL as the ground state.  Our results qualitatively capture main observations in neutron scattering experiments above a very low energy cutoff.

In the second part, we target the exact nature of QSL in KAFM, from the angle of  gauge transformation akin to Laughlin's gedanken experiment.  The entanglement response reveals the presence of emergent Dirac fermion excitations in this system, which unveils the nature of QSL of KAFM is U(1) Dirac QSL. ​

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Bio:

Dr. W. Zhu is working at Theoretical Division of Los Alamos National Lab as a Director's funded postdoc fellow. His current research focus on topological phases of matter in strongly correlated system, including topological orders and fractional excitations in geometrically frustrated quantum magnetism and fractional quantum Hall effect. Dr. W. Zhu is also interested in the applications of quantum information concepts to quantum many-body systems.

Date: 

Thursday, December 14, 2017 - 14:30 to 15:30

Speaker Name: 

Wei Zhu, Theoretical Division, Los Alamos National Laboratory

Location: 

Shull Wollan Center (ORNL Bldg. 8630), Room A202

Host: 

Cristian Batista

Event Type: