Condensed Matter Sack Lunch Seminar

semester, 2015

Tuesday, January 20th 2015
There will be no seminar this week.

Tuesday, January 27th 2015
Speaker: Tim Peterson, University of Minnesota
Subject:  "The Spin Lifetime in Ferromagnet/GaAs Heterostructures"

Tuesday, February 3rd 2015
Speaker: Yang Tang, UMN
Subject: Neutron scattering study of antiferromagnetic fluctuations in HgBa2CuO4+δ

Tuesday, February 10th 2015
Speaker: Brent Perreault, UMN
Subject: Spectroscopy of Dynamics in Spin Liquids

Tuesday, February 17th 2015
Speaker: Chris Conklin, University of Minnesota
Subject: To be announced.

Tuesday, February 24th 2015
APS Practice Talks

Tuesday, March 3rd 2015
There will be no sack lunch this week due to APS March Meeting

Tuesday, March 10th 2015
Speaker: Yangmu Li, UMN
Subject: To be announced.
4:30 pm:
Special Condensed Matter Seminar in 435 Tate Lab of Physics
Speaker:  Alexander Tsirlin, National Institute of Chemical Physics and Biophysics, Tallinn, Estonia
Subject: Unconventional ferrimagnetism driven by the magnetic anisotropy on the kagome lattice

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
There will be no seminar this week.

Tuesday, March 24th 2015
Speaker: Chun Chen, UMN
Subject: Splitting the topological ground-state degeneracy of parafermions in fractional quantum Hall heterostructures

Tuesday, March 31st 2015
Speaker: Gordon Stecklein, UMN
Subject: Spin Transport in CVD Graphene Using Co/AlOx contacts

Tuesday, April 7th 2015
Speaker: Xiaoyu Wang, University of Minnesota
Subject: Probing quantum critical pairing in the iron-based superconductors: a Quantum Monte Carlo study

Tuesday, April 14th 2015
Speaker: Terry Bretz-Sullivan, University of Minnesota
Subject: Collective Charge Transport in Ionic Liquid Strontium Titanate Nanowires

Tuesday, April 21st 2015
Speaker: Biqiong Yu, UMN

Tuesday, April 28th 2015
Speaker: Joseph Sobek, UMN
Subject: Tunneling into the LAO/STO Interface

Tuesday, May 5th 2015
12:20 pm:
Condensed Matter Sack Lunch in Tate Room 435
The sack lunch this week has been cancelled.

Friday, September 11th 2015
Speaker: Xiaowei Zhang, University of Minnesota
Subject: Giant Saturation Magnetization Material Fe16N2 and its Properties

Friday, September 18th 2015
Speaker: Han Fu, University of Minnesota
Subject: Collapse of electrons to a donor cluster in STO

Friday, September 25th 2015
Speaker: Yuting Wang, University of Minnesota
Subject: Entanglement entropy in Su-Schrieffer-Heeger model

Friday, October 2nd 2015
Speaker:  Ziran Wang, University of Minnesota
Subject: Enhanced GMR by Wave Vector Filtering

Friday, October 9th 2015
Speaker: Semere Tadesse, University of Minnesota
Subject: Surface acoustic wave induced optical transparency in photonic crystal cavity

Friday, October 16th 2015
Speaker: Qianhui Shi, University of Minnesota
Subject: Quantum Hall stripes in tilted magnetic fields

Friday, October 23rd 2015
Speaker: Boyi Yang, University of Minnesota
Subject: Ionic liquid gating Sr2IrO4 single crystal

Friday, October 30th 2015
Speaker: Justin Watts, University of Minnesota
Subject: Room Temperature Kondo-Suppressed Spin Accumulation in Cu Non-Local Spin Valves

Friday, November 13th 2015
Speaker: Brent Perreault, University of Minnesota
Subject: Semimetal Physics in Kitaev Spin Liquids

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
Speaker: Yangmu Li, University of Minnesota
Subject: Charge transport of cuprate superconductors: electron- vs. hole-doped

Friday, November 27th 2015
There will be no seminar this week.

Friday, December 4th 2015
Speaker: Tim Peterson, University of Minnesota
Subject: Electrical spin injection in ferromagnet/GaAs/AlGaAs 2DEG structures

Friday, December 11th 2015
Speaker: Taher Ghasimakbari, University of Minnesota
Subject: Simulations of Diblock Copolymers

Friday, December 18th 2015
There will be no seminar this week.

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