Effects of magnetic field and transverse anisotropy on full counting statistics in single-molecule magnet

TL;DR

This paper theoretically investigates how magnetic field orientation and transverse anisotropy influence electron transport statistics in single-molecule magnets, revealing complex behaviors in shot noise and skewness that depend on coupling asymmetry and anisotropy.

Contribution

It provides a detailed theoretical analysis of full counting statistics in SMMs considering arbitrary magnetic field angles and transverse anisotropy, which has not been extensively studied before.

Findings

Shot noise peaks vary with angle and coupling asymmetry.

Small transverse anisotropy can induce super-Poissonian shot noise.

Skewness is more sensitive to angle and anisotropy effects.

Abstract

We have theoretically studied the full counting statistics of electron transport through a single-molecule magnet (SMM) with an arbitrary angle between the applied magnetic field and the SMM's easy axis above the sequential tunneling threshold, since the angle $\theta$ cannot be controlled in present-day SMM experiments. In the absence of the small transverse anisotropy, when the coupling of the SMM with the incident-electrode is stronger than that with the outgoing-electrode, i.e., $\Gamma_{L}/\Gamma_{R}\gg1$, the maximum peak of shot noise first increases and then decreases with increasing $\theta$ from 0 to $0.5\pi$. In particular, the shot noise can reach up to super-Poissonian value from sub-Poissonian value when considering the small transverse anisotropy. For $\Gamma_{L}/\Gamma_{R}\ll1$, the maximum peaks of the shot noise and skewness can be reduced from a super-Poissonian to a sub-Poissonian value with increasing $\theta$ from 0 to $0.5\pi$; the super-Poissonian behavior of the skewness is more sensitive to the small $\theta$ than shot noise, which is suppressed when taking into account the small transverse anisotropy. These characteristics of shot noise can be qualitatively attributed to the competition between the fast and slow transport channels. The predictions regarding of the $\theta$-dependence of high order current cumulants are very interesting for a better understanding electron transport through SMM, and will allow for experimental tests in the near future.