Valley coherence is of great significance for exploring fundamental quantum phenomena and developing next-generation valleytronic devices. Herein, we theoretically investigate the valley quantum interference engineered by inter-Landau level (LL) transitions in black phosphorus (BP) and ${\mathrm{WTe}}_2$ monolayers. In contrast to the non-Landau-quantized regime, valley quantum interference is enhanced by over 20-fold, or even significantly stronger, in virtue of the striking anisotropic environment. Such anisotropy originates from the distinct electron transition probabilities along the armchair and zigzag directions of BP and ${\mathrm{WTe}}_2$ monolayers. Specifically, BP is capable of more effectively strengthening the valley quantum interference response due to its greater directional disparity in electron transition probabilities. The interference fringes also present distinct spectral profiles (e.g., different dip and peak numbers in one interference period) owing to different transition selection rules in BP and ${\mathrm{WTe}}_2$ monolayers. In spite of these discrepancies, normalized interference intensities can be phenomenologically fitted by two exponential functions of magnetic field and LL index for all the transitions $\delta n=n^{\prime }-n=0$, ±2, ±4 (where $n$ and $n^{\prime }$ indicate the LL indexes of the valence and conduction bands, respectively), and the interference spectra exhibit ${\mathrm{C}}_2$ rotational symmetry about the crystallographic azimuthal angle of 90°.

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• Landau levels
• Quantum interference effects
• Shubnikov-de Haas effect
• Valley degrees of freedom
• Valleytronics