Yes, electric susceptibility can be a
tensor, depending on the material's symmetry.
In most materials,
electric susceptibility (χ) is a scalar quantity, meaning it only has one value and does not change with direction. However, for materials that do not have symmetry in all directions, such as
anisotropic materials (materials whose properties differ depending on the direction), the electric susceptibility becomes a
tensor.
In these materials, the polarization (P) in response to an electric field (E) is not necessarily in the same direction as the electric field, and the relationship can be described by a tensor. The general form of the relationship for anisotropic materials is:
\[
\mathbf{P} = \varepsilon_0 \chi \mathbf{E}
\]
Where:
- P is the polarization vector
- E is the electric field vector
- \(\varepsilon_0\) is the permittivity of free space
- χ is the susceptibility tensor (a 3x3 matrix for three-dimensional materials)
This means that in an anisotropic material, the susceptibility may have different components for each direction, and you need to consider a tensor (a matrix) to fully describe the relationship between the polarization and electric field.