Condensed-Matter Physics & Materials Science Seminar
"The 'Higgs' Amplitude Mode in Weak Ferromagnetic Metals"
Presented by Kevin Bedell, Boston College
Thursday, June 6, 2013, 1:30 pm
Small Seminar Room, Bldg. 510
Hosted by: Robert Konik
Using Ferromagnetic Fermi liquid (FFL) theory, Bedell and Blagoev derived the collective low-energy excitations of a weak ferromagnet. They obtained the well-known magnon (Nambu-Goldstone) mode and found a new gapped mode that was never studied in weak ferromagnetic metals. Recently we have identified this mode as the Higgs boson (amplitude mode) of a ferromagnetic metal. This is identified as the Higgs since it can be show that it corresponds to a fluctuation of the amplitude of the order parameter. We use the FFL theory to describe the single particle and collective excitations of the itinerant-electron ferromagnetic material MnSi. By fitting the model with the existing experimental results, we calculate the dynamical structure function and see well-defined peaks contributed from the magnon and the Higgs. Our estimates of the relative intensity of the Higgs amplitude mode suggest that it can be seen in neutron scattering experiments on MnSi.