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Tuesday, January 20th 2015

12:20 pm:

Tuesday, January 27th 2015

12:20 pm:

Tuesday, February 3rd 2015

12:20 pm:

Tuesday, February 10th 2015

12:20 pm:

Tuesday, February 17th 2015

12:20 pm:

Tuesday, February 24th 2015

12:20 pm:

Tuesday, March 3rd 2015

12:20 pm:

Tuesday, March 10th 2015

12:20 pm:

4:30 pm:

The majority of ferrimagnets comprise nonequivalent spin sublattices that produce a net moment, which is an integer fraction of the magnetic moment on one site. We elaborate on an alternative mechanism that yields ferrimagnets with arbitrary net moments produced by a spin canting. This canting originates from the frustration of the spin-1/2 kagome lattice with ferromagnetic nearest-neighbor and antiferromagnetic next-nearest-neighbor couplings, as in the francisite mineral Cu_3 Bi(SeO_3)_2 Cl and its synthetic sibling compounds.

Classical treatment of the francisite spin model with only isotropic (Heisenberg) interactions leads to an infinitely degenerate ground state, where both ferrimagnetic (canted) and antiferromagnetic (spiral) phases have equal energies. Quantum corrections explored by the coupled-cluster method result in a marginal stabilization of the ferrimagnetic state. However, the main driving force behind the unconventional ferrimagnetism turns out to be the magnetic anisotropy of Dzyaloshinsky-Moriya (DM) type. By evaluating both isotropic and anisotropic (DM) terms in the spin Hamiltonian from first-principles DFT calculations, we establish a complete microscopic magnetic model of francisites and compare it to the experiment.

The opportunities for calculating isotropic exchange couplings and magnetic anisotropy parameters from DFT will be discussed.

Tuesday, March 17th 2015

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Tuesday, March 24th 2015

12:20 pm:

Tuesday, March 31st 2015

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Tuesday, April 7th 2015

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Tuesday, April 14th 2015

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Tuesday, April 21st 2015

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Tuesday, April 28th 2015

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Tuesday, May 5th 2015

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Friday, September 11th 2015

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Friday, September 18th 2015

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Friday, September 25th 2015

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Friday, October 2nd 2015

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Friday, October 9th 2015

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Friday, October 16th 2015

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Friday, October 23rd 2015

12:20 pm:

Friday, October 30th 2015

12:20 pm:

Friday, November 13th 2015

12:20 pm:

Semimetals and Spin Liquids are two sought-after states in modern condensed matter physics. In this talk I will discuss the Kitaev spin liquid and its excitations. I will then present Raman scattering as a probe for these exotic states in candidate spin-orbit coupled materials. It turns out that Raman scattering probes a fermionic quasiparticle in this system that realizes effective semimetal physics. Finally, I will speculate about Raman signatures of semimetal surface modes.

Friday, November 20th 2015

12:20 pm:

Friday, November 27th 2015

12:20 pm:

Friday, December 4th 2015

12:20 pm:

Friday, December 11th 2015

12:20 pm:

Friday, December 18th 2015

12:20 pm:

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