[Pw_forum] Spin polarized surface band

[J. D. Burton]

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.

 <mailto:jdburton1 at gmail.com> 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> 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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