Yambo Community Forum

Posted: **Sat May 16, 2026 8:18 am**

Dear all,
I have carefully studied the existing Q&A on the forum as well as the tutorials on the magneto-optical Kerr effect of bulk materials. I have the following questions regarding the calculation of the magneto-optical Kerr effect and circular dichroism of low-dimensional materials:
1、By setting

Code: Select all

BSEprop="abs kerr"
BlongDir
 1 | 0 | 0 |
BSEdips="xy"

we can obtain epsilon_xx and xy. Now, if for systems with low symmetry, epsilon_xx is not equal to yy, and xy is not equal to yx, when we need to calculate yy and yx, do we need to set

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BSEprop="abs kerr"
% BlongDir
 0 | 1 | 0 |
%
BSEdips="yx"

？

2、For the magneto-optical Kerr effect in low-dimensional systems, can the calculation be performed by using "-r" and adding the cutoff?

3、Formally speaking, both the magneto-optical Kerr effect and circular dichroism depend on the off-diagonal elements of epsilon. For non-magnetic chiral materials, can we obtain the result of circular dichroism through the tutorial of the magneto-optical Kerr effect?

Best,
sunxl

Posted: **Tue May 19, 2026 8:36 am**

Dear sunxl,

Point 1: yes.

As explained also here: https://www.lumen-code.org/wiki/index.p ... err_effect

Starting from yambo 5.4, you can also try

Code: Select all

BSEprop="abs kerr asymm"
BlongDir
 1 | 0 | 0 |
BSEdips="xy"

It should return in the .eps file 1/2(eps_xx+eps_yy) and in the .off file 1/2(eps_xy-eps_yx)

Point 2: yes
All features that you can use for a standard BSE run, will work fine also with the kerr effect

Point 3: no
There are two different sources of dichroism: magnetic circular dichroism (MCD) and natural circular dichroism (NCD). The former can be computed via the off-diagonal matrix elements of the dielectric tensor epsilon, the latter is due to the so called beta tensor. Please see here:
https://www.lumen-code.org/wiki/index.p ... References
https://www.lumen-code.org/wiki/index.p ... References

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