Direction of wavevector of kwant.physics.Bands?
Hello, Let's say I have a system, and a lead attached to the left side of the system extending to infinity towards the left. As far as kwant is concerned, the translation invariance vector for the lead points towards the left, i.e. in /negative/ x direction. Now I call `kwant.physics.Bands` or equivalently `kwant.plotter.bands` on this lead. I get a plot of the energy bands, with the wavevector ranging from -π to +π , in units of inverse lattice constants of the lead. My question is the following: What does the positive x-axis of this plot correspond to? Does positive wavevector in this plot correspond to /positive/ x-direction (opposite to the lead translational vector) or to /negative/ x-direction, in parallel with the lead translational vector? I know that e.g. incoming modes must have negative group velocity, but this doesn't answer my question, since I am using a graphene zigzag lead, which means that I have negative group velocities for both positive and negative wavevectors. Also, I have checked the following documentations trying to answer my question: * kwant.physics.Bands * PropagatingModes * FAQ of development documentation page * kwant.plotter.band * |kwant.physics.||modes| |It is still unclear to me whether in my case, positive wavevector corresponds to the positive x-direction of my system or the negative x-direction of my system, due to the lead convention. If this is stated clearly somewhere in the kwant documentation, please excuse me for not finding it, and be kind enough to point me there. P.S.: I need this because I am trying to calculate from which graphene "valley" each incoming mode belongs to. If the k_x wavevector of the incoming valley is postive, then it has valley pseudo-spin ξ=1, but I have to know whether my "positive wavevector" and the lead's positive wavevectors are the same or opposite. Best regards, George Datseris |
Hi George,
We (the Kwant developers) realized that the mode ordering isn't very
clear, and are tracking the fixes in this issue:
https://gitlab.kwant-project.org/kwant/kwant/issues/143
Please take a look at the related changes in the documentation. If you
find those not sufficiently clear, please let us know (e.g. by joining
the issue discussion or replying here).
Best,
Anton
On Fri, Nov 10, 2017 at 4:37 PM, George Datseris
Hello,
Let's say I have a system, and a lead attached to the left side of the system extending to infinity towards the left.
As far as kwant is concerned, the translation invariance vector for the lead points towards the left, i.e. in negative x direction.
Now I call `kwant.physics.Bands` or equivalently `kwant.plotter.bands` on this lead.
I get a plot of the energy bands, with the wavevector ranging from -π to +π , in units of inverse lattice constants of the lead.
My question is the following: What does the positive x-axis of this plot correspond to? Does positive wavevector in this plot correspond to positive x-direction (opposite to the lead translational vector) or to negative x-direction, in parallel with the lead translational vector?
I know that e.g. incoming modes must have negative group velocity, but this doesn't answer my question, since I am using a graphene zigzag lead, which means that I have negative group velocities for both positive and negative wavevectors.
Also, I have checked the following documentations trying to answer my question:
kwant.physics.Bands PropagatingModes FAQ of development documentation page kwant.plotter.band kwant.physics.modes
It is still unclear to me whether in my case, positive wavevector corresponds to the positive x-direction of my system or the negative x-direction of my system, due to the lead convention.
If this is stated clearly somewhere in the kwant documentation, please excuse me for not finding it, and be kind enough to point me there.
P.S.: I need this because I am trying to calculate from which graphene "valley" each incoming mode belongs to. If the k_x wavevector of the incoming valley is postive, then it has valley pseudo-spin ξ=1, but I have to know whether my "positive wavevector" and the lead's positive wavevectors are the same or opposite.
Best regards, George Datseris
participants (2)
-
Anton Akhmerov
-
George Datseris