Re: [Kwant] Problems with band in tutoral 2.5 graphene ( 고운 )
Hi Lee, As Anton pointed out, it is due to the dangling bond. For graphene each unit cell contains two atoms. When you make the lead you actually specify the boundary in space which may take half of an unit cell - this will give you a flat line at zero energy in your band structure and also a small gap. This is not incorrect. The results of nanoribbon from analytical model deals with complete unit cell (it is 2x2 hamiltonian with boundary condition), that is why you can't see it there. I guess you have to fix it manually - either use proper r value or change the width of lead (it is actually 0.4*r) such that each slice of your lead have even number of atoms. Hope it will help. Best, Sumit On 28 February 2016 at 15:02, <kwant-discuss-request@kwant-project.org> wrote:
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Today's Topics:
1. Re: Problems with band in tutoral 2.5 graphene (Anton Akhmerov) 2. Re: Problems with band in tutoral 2.5 graphene ( 고운 ) 3. Re: Problems with band in tutoral 2.5 graphene (Anton Akhmerov)
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Message: 1 Date: Sat, 27 Feb 2016 16:20:50 +0100 From: Anton Akhmerov <anton.akhmerov+kd@gmail.com> To: 고운 <rhdnsi@hanmail.net> Cc: "kwant-discuss@kwant-project.org" <kwant-discuss@kwant-project.org> Subject: Re: [Kwant] Problems with band in tutoral 2.5 graphene Message-ID: < CADr1H-853of8DduXzNGYyCXK0qdhXmXKM7Kdiq_ZL92ajPWsZQ@mail.gmail.com> Content-Type: text/plain; charset=UTF-8
Hi Lee,
What exactly do you want to fix? From your description I didn't notice anything going wrong.
Cheers, Anton
On Sat, Feb 27, 2016 at 6:25 AM, 고운 <rhdnsi@hanmail.net> wrote:
Hello, I am just starting with KWANT. I have a question about the energy
band in lead. In the tutorial "2.5 Beyond square lattices: graphene", the energy band in lead is semimetallic and is consistent with that of zigzag-edge graphene nanoribbon when "r=10" ( default value given in the tutorial). However, when I set r=9 (or a value larger than 10), the energy band in lead becomes insulating and the conductance of scattering region also changes greatly. How can I fix it?
thanks,
Lee
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Message: 2 Date: Sun, 28 Feb 2016 12:32:41 +0900 (KST) From: " 고운 " <rhdnsi@hanmail.net> To: <kwant-discuss@kwant-project.org> Subject: Re: [Kwant] Problems with band in tutoral 2.5 graphene Message-ID: <20160228123241.HM.000000000000rzW@rhdnsi.wwl1454.hanmail.net> Content-Type: text/plain; charset="utf-8"
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Message: 3 Date: Sun, 28 Feb 2016 09:52:50 +0100 From: Anton Akhmerov <anton.akhmerov@gmail.com> To: 고운 <rhdnsi@hanmail.net> Cc: "kwant-discuss@kwant-project.org" <kwant-discuss@kwant-project.org> Subject: Re: [Kwant] Problems with band in tutoral 2.5 graphene Message-ID: < CADr1H-9srdLxt5wjuYDAvZpRNVAN8v7koTZ4zCL68ZrzdAtJBg@mail.gmail.com> Content-Type: text/plain; charset=UTF-8
I think that the energy band in lead should be the semimetallic band of zigzag-edge graphene nanoribbon regardless of the parameter r.
Did you plot the system and the dispersion of the lead? I suspect one of the edges has dangling bonds (corresponding to the "bearded" boundary condition). This would open a gap in the lead band structure.
Anton
If the band in lead is incorrect and changes from metall to insulator
depending on the parameter r, how can i trust the resulting conductance of scattering region ? So, I thought someting is wrong.
Thanks, again
Lee
--------- 원본 메일 ---------
보낸사람: Anton Akhmerov <anton.akhmerov+kd@gmail.com> 받는사람 : 고운 <rhdnsi@hanmail.net> 참조 : "kwant-discuss@kwant-project.org" <kwant-discuss@kwant-project.org> 날짜: 2016년 2월 28일 일요일, 00시 20분 50초 +0900 제목: Re: [Kwant] Problems with band in tutoral 2.5 graphene
Hi Lee,
What exactly do you want to fix? From your description I didn't notice anything going wrong.
Cheers, Anton
On Sat, Feb 27, 2016 at 6:25 AM, 고운 <rhdnsi@hanmail.net> wrote:
Hello, I am just starting with KWANT. I have a question about the
energy band in lead. In the tutorial "2.5 Beyond square lattices: graphene", the energy band in lead is semimetallic and is consistent with that of zigzag-edge graphene nanoribbon when "r=10" ( default value given in the tutorial). However, when I set r=9 (or a value larger than 10), the energy band in lead becomes insulating and the conductance of scattering region also changes greatly. How can I fix it?
thanks,
Lee
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Sumit Ghosh