We predict that the recently discovered quasi-one dimensional superconductors, A2Cr3As3(A=K,Rb), possess strong frustrated magnetic fluctuations and are nearby a novel in-out co-planar magnetic ground state. The frustrated magnetism is very sensitive to c-axis lattice constant and can thus be suppressed by increasing pressure. Our results qualitatively explain strong non-Fermi liquid behaviors observed in the normal state of the superconductors as the intertwining between the magnetism and superconductivity can create a large quantum critical region in quasi-one dimensional systems and also suggest that the materials share similar phase diagrams and superconducting mechanism with other unconventional superconductors, such as cuprates and iron-based superconductors. 74.25.Ha, 74.20.Pq, 74.20.Rp One of major challenges in condensed matter physics is to understand the role of electron-electron correlation in unconventional superconductors. The effect of electron-electron interaction becomes more important as the dimension of a system is lowered. Indeed, many unconventional superconductors discovered in the past are quasi-two dimensional(Q2D) electron systems. The superconductivity in these unconventional superconductors appears in a vicinity to a magnetically ordered state. Magnetic fluctuations which are caused by electron-electron interaction have been widely considered to be responsible for superconductivity and many non-Fermi liquid behaviors in normal states.While there are many representatives of Q2D unconventional superconductors, it has been difficult to find one in quasi-one dimensional(Q1D) systems even if the effect of the electron-electron correlation is expected to be enhanced further. The Q1D superconductors discovered previously, including Bechgaard salts [1,2] , Tl 2 Mo 6 Se 6 [3] and Li 0.9 Mo 6 O 17 [4][5][6][7], are not attributed to 3d-orbital electrons which can exhibt strong electron-electron interaction.Very recently, two novel Q1D materials K 2 Cr 3 As 3 [8] and Rb 2 Cr 3 As 3 [9] have been synthesized and found to be superconducting below the transition temperature 6.1 K and 4.8 K respectively. The structure of A 2 Cr 3 As 3 (A=K,Rb) is characterized by one-dimensional (Cr 3 As 3 ) chains ( Fig.1(a)), which contain Cr 6 distorted octahedral clusters. The alkali metal ions are intercalated between the (Cr 3 As 3 ) chains. Both new materials show strong non-fermi liquid behaviors in normal states, as well as unconventional superconducting properties in superconducting (SC) states. Moreover, just like cuprates and iron-based superconductors, the electronic physics in these new materials are likely attributed to 3d-oribtals of Cr atoms. Therefore the material may exhibit strong magnetism and electron-electron interaction.In this paper, we show that the new materials can be a critical representative of Q1D unconventional superconductors * Electronic address: jphu@iphy.ac.cn where the superconductivity emerges in a vicinity to a novel magnetically ordered state. We predict that the materials ...

We construct minimum effective models to investigate the pairing symmetry in the newly discovered quasione-dimensional superconductor K2Cr3As3. We show that a minimum three-band model based on the d z 2 , dxy and d x 2 −y 2 orbitals of one Cr sublattice can capture the band structures near Fermi surfaces. In both weak and strong coupling limits, the standard random phase approximation (RPA) and mean-field solutions consistently yield the triplet pz-wave pairing as the leading pairing symmetry for physically realistic parameters. The triplet pairing is driven by the ferromagnetic fluctuations within the sublattice. The gap function of the pairing state possesses line gap nodes on the kz = 0 plane on the Fermi surfaces.

Density-functional calculations are carried out to investigate incommensurate magnetic structures and ferroelectric polarization in newly discovered multiferroic material MnI2. The exchange interactions among local moments on Mn are parameterized by mapping the mean-field Heisenberg model on to total energy difference of several magnetic ordering states. The experimentally observed noncollinear magnetic states are well reproduced by using this model and exchange interaction parameters. The direction of polarization experimentally measured is also consistent with the result derived from the symmetry analysis of the magnetically ordered state. In particular, we find that the inter-plane magnetic exchange coupling is pivotal to the emergence of the spiral magnetic structure. This noncollinear magnetic structure, combined with spin-orbit coupling mainly from I ions, is responsible for the appearance of ferroelectric polarization.

Green solvent-treated organic solar cells (OSCs) have demonstrated remarkable advantages in recent years for printing large-area photovoltaic devices. However, the high boiling point and poor solubility of green solvents lead...

We employ low-frequency Raman spectroscopy to study the nearly commensurate (NC) to commensurate (C) charge density wave (CDW) transition in 1T-TaS2 ultrathin flakes protected from oxidation. We identify new modes originating from C phase CDW phonons that are distinct from those seen in bulk 1T-TaS2. We attribute these to CDW modes from the surface layers. By monitoring individual modes with temperature, we find that surfaces undergo a separate, low-hysteresis NC-C phase transition that is decoupled from the transition in the bulk layers. This indicates the activation of a secondary phase nucleation process in the limit of weak interlayer interaction, which can be understood from energy considerations.