Bi2Se3 GW band structure: how can I remove the Γ-point dimple?

[Jun Inagaki]

Hi,

I have finally obtained the GW band structure of Bi2Se3 around Γ, but I still see a camel-back structure near VBM (attahced..).
My goal is to obtain a smooth “mountain-top” valence band at Γ, similar to the reported GW result.

I included a sufficiently large band window for the off-diagonal self-energy calculation.

Current paramteres are in below:
* Off-diagonal Σ band window: band 31 to band 62
* VBM: band 48
* Plane-wave cutoff: 100 Ry
* Number of bands for ε calculation: 1001
* Number of pseudobands: 255
* Epsilon cutoff: 15 Ry

The attached plot compares the result without and with the off-diagonal self-energy correction. The off-diagonal correction improves the band shape slightly, but the dimple is still not fully resolved.

Could you please advise me on which parameter is most likely to control this Γ-point dimple?

- Planewave cutoff
- Number of bands for Epsilon (pseudobands)
- epsilon cutoff

or some other crucial setting?
Any comments or suggestions would be greatly appreciated.

Best regards,
Jun
HiSOR, Hiroshima University