Weak hyperfine interactions and spin-orbit coupling (SOC) in organic materials result in long spin lifetimes, which is very promising for spintronics. On the other hand, they also make it challenging to achieve spin polarization, which is of crucial importance for spintronics devices. To overcome this obstacle, we have proposed a physical model for spin-polarized electron transport through a chiral molecule based on the chiral-induced spin selectivity. Because the transport in the chiral molecule is not an isolated one, but rather an electron coupled to its surrounding lattice distortions, namely, a spatial localized polaron, an indispensable polaron effect is incorporated in our model. We show that the polaron transport through the chiral molecule exhibits a spin-momentum-locked feature. Interestingly, no matter what their initial spin state is, all of the polarons could transmit through the molecule with their spins being aligned to the same orientation due to the effective “inverse Faraday effect.” The coexistence of the electron-lattice coupling and SOC results in the spin and lattice being coupled, which leads to a strongly enhanced spin coherence and then a very high spin polarization of $70\%$. In addition, the effects of the helix pitch, polaron size, and drift velocity on spin polarization are also discussed. Our results open the possibility of using chiral molecules in spintronics applications and offer a paradigm for information processing and transmission.

Transport process of a charged polaron under a linearly increasing electric field in conjugated polymers is investigated by using a nonadiabatic evolution method. It is found that the behavior of a polaron depends not only upon the strength of the field but also upon the mode of the application of the field. A polaron can conserve even under a strong field if the field is applied slowly. The result is compared with that of the adiabatic approximation and it is obtained that the nonadiabatic critical time is much larger than the adiabatic value. Dependence of the applying mode of the external electric field on the polaron dissociation and the transition of its velocity from the subsonic to supersonic value are further described.

We study theoretically the geometric quantum speed limits (QSLs) of open quantum systems under Markovian dynamical evolution. Three types of QSL time bounds are introduced based on the geometric inequality associated with the dynamical evolution from an initial state to a final state. By illustrating three types of QSL bounds at the cases of presence or absence of system driving, we demonstrate that the unitary part, dominated by system Hamiltonian, supplies the internal motivation for a Markovian evolution which deviates from its geodesic. Specifically, in the case of unsaturated QSL bounds, the parameters of the system Hamiltonian serve as the eigen-frequency of the oscillations of geodesic distance in the time domain and, on the other hand, drive a further evolution of an open quantum system in a given time period due to its significant contribution in dynamical speedup. We present physical pictures of both saturated and unsaturated QSLs of Markovian dynamics by means of the dynamical evolution trajectories in the Bloch sphere which demonstrates the significant role of system Hamiltonian even in the case of initial mixed states. It is further indicated that whether the QSL bound is saturated is ruled by the commutator between the Hamiltonian and reduced density matrix of the quantum system. Our study provides a detailed description of QSL times and reveals the effects of system Hamiltonian on the unsaturation of QSL bounds under Markovian evolution.

Hydrogenated graphene becomes more stable when hydrogen atoms are adsorbed on graphene from both sides due to the increased carbon–carbon sp³ hybridization.

Spin-polarized current through a ferromagnetic/organic interface was studied theoretically. This study was stimulated by recent experiments on ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_3∕{\mathrm{Alq}}_3∕\mathrm{Co}$ and ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_3∕\mathrm{sexithienyl}∕{\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_3$ structures. According to the spin-diffusion equation, the current spin polarization was obtained by assuming that spin polarons as well as spinless bipolarons to be the carriers in the organic semiconductor. It was found that polarons are the effective spin carriers of a spin-polarized current, even though they constitute only a fraction of all carriers. Effects of interfacial electrochemical-potential difference and conductivity matching on spin polarization of the current are discussed.