We present an efficient method for evaluating current-induced forces in nanoscale junctions, which naturally integrates into the non-equilibrium Green's function formalism implemented within density functional theory. This allows us to perform dynamical atomic relaxation in the presence of an electric current while also evaluating the current-voltage characteristics. The central idea consists in expressing the system energy density matrix in terms of Green's functions. In order to validate our implementation we perform a series of benchmark calculations, both at zero and finite bias. Firstly we evaluate the current-induced forces acting over an Al nanowire and compare them with previously published results for fixed geometries. Then we perform structural relaxation of the same wires under bias and determine the critical voltage at which they break. We find that, while a perfectly straight wire does not break at any of the voltages considered, a zigzag wire is more fragile and snaps at 1.4 V, with the Al atoms moving against the electron flow. Finally we demonstrate the capability of our scheme to tackle the electromigration problem by studying the current-induced motion of a single Si atom covalently attached to the sidewall of a (4,4) armchair single-walled carbon nanotube. Our calculations indicate that if Si is attached along the current path, then current-induced forces can induce migration. In contrast, if the bonding site is away from the current path, then the adatom will remain stable regardless of the voltage. An analysis based on decomposing the total force into a wind and an electrostatic component, as well as on a detailed evaluation of the bond currents, shows that this remarkable electromigration phenomenon is due solely to the position-dependent wind force.
Ab-initio transport across Bismuth Selenide surface barriers
利用大规模从头算输运模拟方法研究了台阶边势垒对Bi $_2$ Se $_3$（111）拓扑表面态散射性质的影响.我们的结果表明，抑制完美的后向散射，而所有其他的散射过程，这并不需要一个完整的自旋和动量反转，是允许的。此外，我们发现表面态的自旋在穿过势垒时会产生出平面分量。我们的计算揭示了准束缚态的存在，在附近的表面势垒，这出现在一个增强的状态密度的形式在对应的拓扑状态的能量窗口。对于双势垒，我们证明了量子阱态的形成。为了补充我们的第一性原理的结果，我们构建了一个二维的低能量有效模型，并表明，带弯曲的散射过程中起着重要的作用。我们的研究结果进行了讨论的背景下，最近的一些实验工作。
A quantum coherent approach to transport and noise in double barrier resonant diodes: shot noise a way to distinguish coherent from sequential tunneling
Quantum tunneling and defect-induced transport modulation in twisted bilayer graphene superlattices
Multidisciplinary Research and Innovation Laboratory, EMAFI team, Polydisciplinary Faculty, Sultan Moulay Slimane University（苏丹穆莱·斯莱曼大学多学科创新研究实验室）；Advanced Laboratory in Industrial Engineering and Logistics (LARILE) National School of Electrical and Mechanical Engineering, Hassan II University（哈桑二世大学电气机械工程学院工业工程与物流高级实验室）
