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Phonon linewidth constant 0 at Gamma for a metal?
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Joined: Thu Jul 14, 2016 6:09 am
Posts: 37
University: POSTECH (Korea)
Phonon linewidth constant 0 at Gamma for a metal?
Dear all,

I have a strange problem: I have a metallic slab (Ag 100). When I calculate the electron-phonon coupling and phonon linewidth the latter is always constant 0 at q1=Gamma. Away from gamma (even a small step is enough q2=0.01 |Gamma-X|) this is no longer the case as you can see below.

Code:
# Phonon frequency and phonon lifetime in meV
# Q-point  Mode   Phonon freq (meV)   Phonon linewidth (meV)
1     1      0.14018096E-05      0.0000000000E+00
1     2      0.15037978E-05      0.0000000000E+00
1     3      0.15678200E-05      0.0000000000E+00
1     4      0.32037347E+01      0.0000000000E+00
1     5      0.32037347E+01      0.0000000000E+00
1     6      0.50111038E+01      0.0000000000E+00
1     7      0.50111038E+01      0.0000000000E+00
1     8      0.52040993E+01      0.0000000000E+00
1     9      0.80325952E+01      0.0000000000E+00
1    10      0.80325952E+01      0.0000000000E+00
1    11      0.81943124E+01      0.0000000000E+00
1    12      0.10998395E+02      0.0000000000E+00
1    13      0.10998395E+02      0.0000000000E+00
1    14      0.12627565E+02      0.0000000000E+00
1    15      0.12627565E+02      0.0000000000E+00
1    16      0.12875931E+02      0.0000000000E+00
1    17      0.16689456E+02      0.0000000000E+00
1    18      0.18803622E+02      0.0000000000E+00
1    19      0.25815292E+02      0.0000000000E+00
1    20      0.25815292E+02      0.0000000000E+00
1    21      0.32939073E+02      0.0000000000E+00
1    22      0.52623817E+02      0.0000000000E+00
1    23      0.52623817E+02      0.0000000000E+00
1    24      0.54967801E+02      0.0000000000E+00
1    25      0.54967801E+02      0.0000000000E+00
1    26      0.57559031E+02      0.0000000000E+00
1    27      0.64030663E+02      0.0000000000E+00
2     1     -0.57327299E+00      0.0000000000E+00
2     2      0.50717746E-01      0.0000000000E+00
2     3      0.52337994E+00      0.0000000000E+00
2     4      0.31996073E+01      0.1518331503E-03
2     5      0.32052218E+01      0.1518331503E-03
2     6      0.49762293E+01      0.1529582313E-01
2     7      0.50116566E+01      0.9400167807E-05
2     8      0.52458229E+01      0.1173353266E+00
2     9      0.80309468E+01      0.1160566942E-02
2    10      0.80326033E+01      0.1160566942E-02

mode 9 for example has \omega_{q\nu}=8 meV; there is plenty of "DOS" 8 meV above Ef for vertical (q=0) transitions in my system and I think the first equation here: http://epw.org.uk/Documentation/Electron-phononCoupling should definitely yield some non-zero elements;

I have tested different values for degaussq/w but above behaviour does not change.

Your help is very much appreciated!

Best,
Chris
Since a metal has plenty of states below and above Ef I was curious why the linewidth would be constant 0 in this case - did I do something wrong?

Mon Sep 30, 2019 6:42 am
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