Single Helical Molecule Research Articles

Roles of quantum interference in modulating the spin-polarized transport induced by single-helical molecules

We investigate the spin-polarized transport through the systems with protein-like single-helical molecules. It shows that the spin polarization property and efficiency tightly depend on the geometries of the systems of single-helical molecules. When one molecule is serially coupled to two leads, the inter-lead coupling assists to magnify the spin polarization efficiency, and the polarization direction can be adjusted by the local magnetic flux. However in the other geometries, no apparent spin polarization is driven, such as the T-shaped structure with inter-lead coupling and parallel coupled structures. These results reflect the nontrivial effect of structure-dependence quantum interference on the spin polarization driven by the single-helical molecule.

Thermoelectric and thermospin properties in a quantum ring with an embedded protein-like single-helical molecule

We investigate the thermoelectric and thermospin effects in a quantum ring whose arms are embedded by one protein-like single-helical molecule and one quantum dot, respectively. It shows that both the thermoelectric and thermospin effects are very distinct in this system. If one local magnetic flux is introduced through this ring, the thermospin effect can be efficiently enhanced, accompanied by the weakness of thermoelectric effect. Therefore, this work can be helpful for the achievement of the thermoelectric and thermospin effects, respectively.

Spin-polarized transport through a quantum ring with an embedded protein-like single-helical molecule.

We investigate the spin-polarized electron transport through a quantum ring whose arms are embedded by one protein-like single-helical molecule and one quantum dot, respectively. It is found that the inter-arm quantum interference leads to the enhancement of the spin polarization in this structure. Moreover, when local magnetic flux is applied through the ring, the spin polarization in the electron transport process, including the polarization strength and direction, can be further adjusted. Next in the finite-bias case, the spin polarization is also apparent and can be tuned by changing the magnetic flux or the dot level. This work provides a new scheme to manipulate the spin transport based on the single-helical molecule.

Topological states and quantized current in helical organic molecules

We report a theoretical study of electron transport along helical molecules under an external electric field, which is perpendicular to the helix axis of the molecule. Our results reveal that the topological states could appear in single-helical molecule and double-stranded DNA in the presence of the perpendicular electric field. And these topological states guarantee adiabatic charge pumping across the helical molecules by rotating the electric field in the transverse plane and the pumped current at zero bias voltage is quantized. In addition, the quantized current constitutes multiple plateaus by scanning the Fermi energy as well as the bias voltage, and hold for various model parameters, since they are topologically protected against perturbations. These results could motivate further experimental and theoretical studies in the electron transport through helical molecules, and pave the way to detect topological states and quantized current in the biological systems.

Highly-polarized spin currents through protein-like single-helical molecules

Electronic transport through a protein-like single-helical molecule is theoretically studied. By introducing an additional terminal to couple to the molecule, we construct a two-channel mesoscopic circuit, and then calculate the charge and spin currents in the two drain terminals. It is found that in one drain terminal, one pure spin current has an opportunity to appear without any accompanying charge current. Besides, the polarization direction of the spin current can be inverted. With respect to the current in the other drain, it is also found to be highly polarized, with its polarization direction different from that in the other terminal. These results suggest that the protein-like single-helical molecule is a promising candidate for building the two-channel setup in spintronics.

Enhancement of spin polarization in transport through protein-like single-helical molecules

We investigate the spin-polarized electron transport through the single-helical molecules connected with two normal metallic leads. On the basis of an effective model Hamiltonian, influences of the structural parameters on the conductance and the spin polarization are calculated by using the Landauer–Buttiker formula. The optimal structural parameters for the maximal spin polarization are analyzed. Our results show that the dephasing term is an important factor to enhance the spin polarization, in addition to the intrinsic parameters of the single-helical molecule. This work can be helpful in optimizing the spin polarization in the protein-like single-helical molecules.

Spin-dependent transport through a chiral molecule in the presence of spin-orbit interaction and nonunitary effects

Recent experiments have demonstrated the efficacy of chiral helically shaped molecules in polarizing the scattered electron spin, an effect termed as chiral-induced spin selectivity (CISS). Here we solve a simple tight-binding model for electron transport through a single helical molecule, with spin-orbit interactions on the bonds along the helix. Quantum interference is introduced via additional electron hopping between neighboring sites in the direction of the helix axis. When the helix is connected to two one-dimensional single-mode leads, time-reversal symmetry prevents spin polarization of the outgoing electrons. One possible way to retrieve such a polarization is to allow leakage of electrons from the helix to the environment, via additional outgoing leads. Technically, the leakage generates complex site self-energies, which break unitarity. As a result, the electron waves in the helix become evanescent, with different decay lengths for different spin polarizations, yielding a net spin polarization of the outgoing electrons, which increases with the length of the helix (as observed experimentally). A maximal polarization can be measured at a finite angle away from the helix axis.