ELFT HÍRADÓ

[tcsaba AT eik.bme.hu]

                     M E G H Í V Ó - I N V I T A T I O N

      Seminar series of the Department of Theoretical Physics at the
            Budapest University of Technology and Economics


                               Rex Lundgren
                       (University of Texas at Austin)

                  Landau Theory of Helical Fermi Liquids


We construct a phenomenological Landau theory for the two-dimensional  
helical Fermi liquid found on the surface of a three-dimensional  
time-reversal invariant topological insulator. In the presence of  
rotation symmetry, interactions between quasiparticles are described  
by ten independent Landau parameters per angular momentum channel, by  
contrast with the two (symmetric and antisymmetric) Landau parameters  
for a conventional spin-degenerate Fermi liquid. We project  
quasiparticle states onto the Fermi surface and obtain an effectively  
spinless, projected Landau theory with a single projected Landau  
parameter per angular momentum channel that captures the spin-momentum  
locking or nontrivial Berry phase of the Fermi surface. As a result of  
this nontrivial Berry phase, projection to the Fermi surface can  
increase or lower the angular momentum of the quasiparticle  
interactions. We derive equilibrium properties, criteria for Fermi  
surface instabilities, and collective mode dispersions in terms of the  
projected Landau parameters. We briefly discuss experimental means of  
measuring projected Landau parameters.


Idöpont: 2016. február 26., 10:15
Helyszín: BME Fizikai Intézet, Elméleti Fizika Tanszék,
Budafoki út 8. F-épület, III lépcsöház, szemináriumi szoba


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