[Pw_forum] Spin polarized surface band

[Peng Chen]

Dear Professor Burton,

Thank you very much for the reply. Does that mean surface band should be
doubly degenerate, whereas bulk bands are quadruply degnerate, otherwise
how do we identify the surface state? In my calculated results, almost all
bands are just doubly degenerate.

And from literature, the sign of spin moment in Gamma-M  direction is
opposite to that in Gmma-K  direction, whereas, there is no any trend in my
result.I also checked sigma(y) and sigma(z) component, there is also no
trend.


On Thu, Feb 20, 2014 at 10:56 AM, J. D. Burton <jdburton1 at gmail.com> wrote:

> Hi Peng,
>
>
>
> Each band is doubly-degenerate because your slab has two surfaces: A
> spin-polarized pair of bands for the top surface, and an
> oppositely-spin-polarized pair of bands for the bottom surface.
>
>
>
> Cheers,
>
> J. D.
>
>
>
>
>
> ************************************
>
> J. D. Burton, Ph.D.
>
> jdburton1 at gmail.com
>
> Research Assistant Professor
>
> University of Nebraska Lincoln
>
> Physics and Astronomy
>
> Office Ph. (402) 472 2499
>
> Mobile Ph. (402) 419 9918
>
> 310A Jorgensen Hall
>
> CV: http://tinyurl.com/2avltsc
>
> ************************************
>
> "The job of a scientist is to generate wrong ideas as fast as possible."
>
> -- Murray Gell-Mann
>
>
>
> *From:* pw_forum-bounces at pwscf.org [mailto:pw_forum-bounces at pwscf.org] *On
> Behalf Of *Peng Chen
> *Sent:* Monday, February 17, 2014 8:11 PM
> *To:* PWSCF Forum
> *Subject:* [Pw_forum] Spin polarized surface band
>
>
>
> Hello Everyone,
>
>
>
> Bi2Se3 slab with 6 quintuple layers is calculated. It is supposed to have
> spin polarized non-degenerate surface bands. However, in the calculated
> results, each band is doubly degenerated including surface band, as shown
> in the left panel of attached figure. And the spin components (sigma x)
> have opposite sign for degenerated surface band (S1). The input is listed
> below. I am not sure if I am doing the right thing. Any suggestions are
> welcome!
>
>
>
> &control
>
>     calculation='scf'
>
>     wf_collect=.TRUE.
>
>     restart_mode='from_scratch',
>
>     prefix='BiSe.6QL.pbe.spin',
>
>     pseudo_dir = '/data/espresso-5.0/pseudo/',
>
>     outdir='/data/scratch/'
>
>  /
>
>  &system
>
>     ibrav=4, celldm(1)=7.8196867, celldm(3)=17
>
>      nat=30, ntyp=2,
>
>          noncolin=.TRUE, lspinorb=.TRUE.
>
>       starting_magnetization(1)=-0.1,
>
>  ecutwfc = 60, ecutrho = 600,nbnd=360
>
>   occupations='smearing', smearing='mv', degauss=0.015
>
>  /
>
>
>
>  &electrons
>
>     conv_thr = 1.0e-7
>
>     mixing_mode='local-TF'
>
>     mixing_beta = 0.7
>
>  /
>
>
>
> ATOMIC_SPECIES
>
>  Bi 208.98040 Bi.rel-pbe-dn-rrkjus_psl.1.0.0.UPF
>
>  Se  78.96  Se.rel-pbe-n-rrkjus_psl.1.0.0.UPF
>
>
>
> ATOMIC_POSITIONS angstrom
>
> Se 0 0 5.899840007
>
> ......
>
> Se 2.069 1.194537707 60.92682666
>
> K_POINTS (automatic)
>
>  10 10 1 0 0 0
>
>
>
>
>
> --
>   Best Regards.
>         Peng
>
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>



-- 
  Best Regards.
        Peng
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