  We have introduced the auxetic effect in MBP-analog Sb for the first time,
and achieve NPR modulations on monolayer As and Sb via first-principles
calculation. Comparing with As, the monolayer Sb is phonon unstable. By
applying an uniaxial strain along each directions, we discovered a
zigzag-vertical reversibility on out-of-plane NPR, and the NPR values for
monolayer As and Sb are simulated to be -0.125/-0.172 and -0.036/-0.063 by
applying strain along zigzag/vertical directions. The NPR values could be
significantly manipulated by applying vertical electrical fields, as increased
up to 70.3% for monolayer As and decreased up to 55.6% for monolayer Sb. Such
intrinsic NPR and electric field modulation could make those monolayers
potential applications in auxetic optoelectronic devices, electrodes and
sensors, leading to novel multi-functionalities.
