Dynamical correlation functions and the related physical effects in three-dimensional Weyl/Dirac semimetals

We present a unified derivation of the dynamical correlation functions including density-density, density-current and current-current, of three-dimensional Weyl/Dirac semimetals by use of the Passarino-Veltman reduction scheme at zero temperature. The generalized Kramers-Kronig relations with arbitrary order of subtraction are established to verify these correlation functions. Our results lead to the exact chiral magnetic conductivity and directly recover the previous ones in several limits. We also investigate the magnetic susceptibilities, the orbital magnetization and briefly discuss the impact of electron interactions on these physical quantities within the random phase approximation. Our work could provide a starting point for the investigation of the nonlocal transport and optical properties due to the higher-order spatial dispersion in three-dimensional Weyl/Dirac semimetals.Comment: 21 pages, 3+1 figures, 1 table. Accepted in PR

Entropy stabilizes floppy crystals of mobile DNA-coated colloids

Grafting linkers with open ends of complementary single-stranded DNA makes a flexible tool to tune interactions between colloids,which facilitates the design of complex self-assembly structures. Recently, it has been proposed to coat colloids with mobile DNA linkers, which alleviates kinetic barriers without high-density grafting, and also allows the design of valency without patches.However, the self-assembly mechanism of this novel system is poorly understood.Using a combination of theory and simulation, we obtain phase diagrams forthe system in both two and three dimensional spaces, and find stable floppy squareand CsCl crystals when the binding strength is strong, even in the infinite bindingstrength limit. We demonstrate that these floppy phases are stabilized by vibrational entropy, and "floppy" modes play an important role in stabilizing the floppy phases for the infinite binding strength limit. This special entropic effect in the self-assembly of mobile DNA-coated colloids is very different from conventional molecular self-assembly, and it offers new axis to help design novel functional materials using mobile DNA-coated colloids.Comment: Accepted in Physical Review Letter

RKKY interaction in three-dimensional electron gases with linear spin-orbit coupling

We theoretically study the impacts of linear spin-orbit coupling (SOC) on the Ruderman-Kittel-Kasuya-Yosida interaction between magnetic impurities in two kinds of three-dimensional noncentrosymmetric systems. It has been found that linear SOCs lead to the Dzyaloshinskii-Moriya interaction and the Ising interaction, in addition to the conventional Heisenberg interaction. These interactions possess distinct range functions from three dimensional electron gases and Dirac/Weyl semimetals. In the weak SOC limit, the Heisenberg interaction dominates over the other two interactions in a moderately large region of parameters. Sufficiently strong Rashba SOC makes the Dzyaloshinskii-Moriya interaction or the Ising interaction dominate over the Heisenberg interaction in some regions. The change in topology of the Fermi surface leads to some quantitative changes in periods of oscillations of range functions. The anisotropy of Ruderman-Kittel-Kasuya-Yosida interaction in bismuth tellurohalides family BiTe$X$ ($X$ = Br, Cl, and I) originates from both the specific form of Rashba SOC and the anisotropic effective mass. Our work provides some insights into understanding observed spin textures and the application of these materials in spintronics.Comment: 11 pages, 4 figures, Final Version in PR