Fig. 2: Ferroelectric transition in bilayer and trilayer WTe2. | npj Computational Materials

Fig. 2: Ferroelectric transition in bilayer and trilayer WTe2.

From: Ferroelectric nonlinear anomalous Hall effect in few-layer WTe2

Fig. 2

ac ferroelectric transition in bilayer WTe2. The two opposite ferroelectric states (−mFE and +mFE) in bilayer are transformed through a glide plane operation \(\left\{ {{\cal{M}}_z{\mathrm{|}}t_a} \right\}\), that is, a mirror operation \({\cal{M}}_z\) followed by an in-plane shift along x by ta with \(t_a = \frac{1}{2}a\). The intermediate PE state C2v point group, thus its out-of-plane polarization with vanishes due to the glide plane \(\left\{ {{\cal{M}}_z|\frac{1}{2}a} \right\}\) symmetry. df ferroelectric transition in trilayer WTe2. The two opposite ferroelectric states (−iFE and +iFE) in trilayer are related to each other through an inversion operation \(\left\{ {{\cal{I}}{\mathrm{|}}0} \right\}\). The intermediate PE state of trilayer WTe2 has C2h point group, thus its out-of-plane polarization also vanishes due to inversion symmetry. The red and green vertical dashed lines show the relative shift ±dx between adjacent WTe2 layers. The corresponding in-plane shift is very small (dx ≈ 20 pm), therefore it is exaggerated in the above plots for illustrative purpose.

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