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:[email protected]] 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: http://pwscf.org/pipermail/pw_forum/attachments/20140220/c1a6a14b/attachment.html
