The experiment that the high spin selectivity and the length-dependent spin polarization are observed in double-stranded DNA [Science 331, 894 (2011)], is elucidated by considering the combination of the spin-orbit coupling, the environment-induced dephasing, and the helical symmetry. We show that the spin polarization in double-stranded DNA is significant even in the case of weak spin-orbit coupling, while no spin polarization appears in single-stranded DNA. Furthermore, the underlying physical mechanism and the parameter dependence of the spin polarization are studied.

We report on a theoretical study of spin-dependent electron transport through single-helical molecules connected by two nonmagnetic electrodes, and explain the experiment of significant spin-selective phenomenon observed in α-helical protein and the contradictory results between the protein and single-stranded DNA. Our results reveal that the α-helical protein is an efficient spin filter and the spin polarization is robust against the disorder. These results are in excellent agreement with recent experiments [Mishra D, et al. (2013) Proc Natl Acad Sci USA 110(37):14872–14876; Göhler B, et al. (2011) Science 331(6019):894–897] and may facilitate engineering of chiral-based spintronic devices.

The Goos-Hänchen (GH) shift and the Imbert-Fedorov (IF) shift are optical phenomena which describe the longitudinal and transverse lateral shifts at the reflection interface, respectively. Here, we predict the GH and IF shifts in Weyl semimetals (WSMs)—a promising material harboring low energy Weyl fermions, a massless fermionic cousin of photons. Our results show that the GH shift in WSMs is valley independent, which is analogous to that discovered in a 2D relativistic material—graphene. However, the IF shift has never been explored in nonoptical systems, and here we show that it is valley dependent. Furthermore, we find that the IF shift actually originates from the topological effect of the system. Experimentally, the topological IF shift can be utilized to characterize the Weyl semimetals, design valleytronic devices of high efficiency, and measure the Berry curvature.

We study the Josephson effect in the spin-singlet superconductor/altermagnet/spin-triplet superconductor junctions using the Green's function method. The current-phase difference relationships in the junctions strongly depend on the orientation of altermagnet and the types of the Cooper pairs. For the orientation angle equal to odd multiples of $\pi /4$, the current-phase difference relationships are of the $sin2\varphi$ type, which are irrespective of the pairing wave functions in superconductors. For the other orientation angles, the emergence of the lowest order current becomes possible and its form, $sin\varphi$ or $cos\varphi$, depends on the pairing wave functions in superconductors. The ${\varphi }_0$ phase and the $0\text{−}\pi$ transition can be realized in our junctions due to the appearance of the lowest order current. The selection rules for the lowest order current are presented. The symmetric relations satisfied by the current-phase difference relationships are analyzed through considering the transformations of the junctions under the mirror reflection, the time-reversal and the spin-rotation operations. Our results not only provide a method to detect the intrinsic spin-triplet superconductivity but also possess application values in the design of the field-free quantum devices.

The field-free and highly efficient diodes with the nonreciprocity of supercurrent are believed to be the core block of superconducting computing devices without dissipation. In this paper, we propose a Josephson diode based upon altermagnets with vanishing net macroscopic magnetization. The nonreciprocity of supercurrent can be realized without applying any external magnetic field or ferromagnetic exchange field, which can avoid the magnetic cross-talk between the basic elements of the devices. A high efficiency exceeding $40\%$ can be obtained, and the efficiency shows high stability when the structure parameters are changed. The diode efficiency is antisymmetric about the relative orientation angle of the superconducting leads, so that its sign can easily be inverted by adjusting the relative orientation angle. The symmetries satisfied by the current-phase difference relations and the diode efficiency are analyzed by considering the transformations of the junctions under the time reversal, the spin rotation, and the mirror reflection operations. The high efficiency and the high stability of the Josephson diode effect in our junctions make it possible to design field-free dissipationless diode devices.

We report spin-selective tunneling of electrons along double-stranded DNA sandwiched between nonmagnetic leads. On the basis of a model Hamiltonian which contains spin-orbit interaction and dephasing, the conductance and the spin polarization are calculated for natural and artificial DNA molecules by using the Landauer-Büttiker formula. Our results reveal that the spin filtration efficiency strongly depends on the DNA sequence and is dominated by its end segment. Both genomic and artificial DNA molecules could be efficient spin filters. The spin-filtering effects are sensitive to point mutation which occurs in the end segment. These results are in good agreement with recent experiments and are robust against various types of disorder, and could help for designing DNA-based spintronic devices.