ELFT HÍRADÓ

[Edina Szirmai <eszirmai AT phy.bme.hu>]

                              MEGHÍVÓ

         az MTA-BME "Egzotikus Kvantum Fázisok"
          kutatócsoport következő szemináriumára


                           Dimitrie Culcer
      (The University of New South Wales, Sydney)

       Weak antilocalisation in topological insulators
                  with strong spin-orbit scattering


Kivonat:

Topological insulators (TI) have revolutionised our understanding of
insulating behaviour. They are insulators in the bulk but conducting along
their surfaces, thanks to surface states in which the spin and the charge
are strongly coupled by means of the spin-orbit interaction. Much of the
recent research on TI focuses on overcoming the transport bottleneck [1],
namely the fact that surface state transport is overwhelmed by bulk
transport stemming from unintentional doping. The key to overcoming this
bottleneck is identifying unambiguous signatures of surface state
transport. This talk will discuss one such signature, which is manifest in
the coherent backscattering of electrons in TI. Because of the strong
spin-orbit coupling in TI one expects to observe weak antilocalisation
rather than weak localisation, meaning that coherent backscattering
increases the electrical conductivity [2]. The features of this effect,
however, are rather subtle, because in TI the impurities have strong
spin-orbit coupling as well, greatly increasing the complexity of the
problem [3]. I will show that spin-orbit coupled impurities introduce an
additional time scale, which is expected to be shorter than the dephasing
time, and the resulting conductivity has a linear dependence on the
carrier number
density, a behaviour hitherto unknown in 2D electron systems. The result we
predict is directly observable experimentally and would provide a smoking
gun test of surface transport. Furthermore, I will also briefly discuss the
effect of electron-electron interactions on transport in this regime.


[1] D. Culcer, Physica E 44, 860 (2012).

[2] G. Tkachov and E. M. Hankiewicz, Phys. Rev. B 84, 035444 (2011).

[3] W. Liu, P. Adroguer, X. Bi, E. M. Hankiewicz, and D. Culcer, to be
published.



Az előadás helye:  BME F III. épület, mfsz, szemináriumi szoba.
Ideje: 2015. június 15. hétfő, 14:15.


Minden érdeklődőt szeretettel várunk!



                       Szirmai Edina


-- 
Edina Szirmai
Department of Theoretical Physics,
Budapest University of Technology and Economics
Budafoki ut 8.
Budapest, Hungary
Tel:(+36-1) 463-4107
Fax:(+36-1) 463-3567
www.phy.bme.hu/~eszirmai