Gate-tunable pairing channels in superconducting non-centrosymmetric oxides nanowires

Two-dimensional SrTiO3-based interfaces stand out among non-centrosymmetric superconductors due to their intricate interplay of gate-tunable Rashba spin-orbit coupling and multi-orbital electronic occupations, whose combination theoretically prefigures various forms of non-standard superconductivity. By employing superconducting transport measurements in nano-devices we present strong experimental indications of unconventional superconductivity in the LaAlO3/SrTiO3 interface. The central observations are the substantial anomalous enhancement of the critical current by small magnetic fields applied perpendicularly to the plane of electron motion, and the asymmetric response with respect to the magnetic field direction. These features cannot be accommodated within a scenario of canonical spin-singlet superconductivity. We demonstrate that the experimental observations can be described by a theoretical model based on the coexistence of Josephson channels with intrinsic phase shifts. Our results exclude a time-reversal symmetry breaking scenario and suggest the presence of anomalous pairing components that are compatible with inversion symmetry breaking and multi-orbital physics.

Crystal structure of a trifluoromethyl benzoato quadruple-bonded dimolybdenum complex

The study of quadruple bonds between transition metals, in particular those of dimolybdenum, has revealed much about the two-electron bond. The solid-state structure of the quadruple-bonded dimolybdenum(II) complex tetrakis(μ-4-trifluoromethylbenzoato-κ2 O:O′)dimolybdenum(II) 0.762-pentane 0.238-tetrahydrofuran solvate, [Mo2(p-O2CC6H4CF3)4·2THF]·0.762C5H12·0.238C4H8O or [Mo2(C8H4F3O2)4(C4H8O)2]·0.762C5H12·0.238C4H8O is reported. The complex crystallizes within a triclinic cell and low symmetry (P\overline{1}) results from the intercalated pentane/THF solvent molecules. The paddlewheel structure at 100 K has inversion symmetry and comprises four bridging carboxylate ligands encases the Mo2(II,II) core that is characterized by two axially coordinated THF molecules and an Mo—Mo distance of 2.1098 (7) Å.

Extremely high upper critical field in BiCh2-based (Ch: S and Se) layered superconductor LaO0.5F0.5BiS2−xSex (x = 0.22 and 0.69)

Centrosymmetric compounds with local inversion symmetry breaking have tremendously interesting and intriguing physical properties. In this study, we focus on a BiCh2-based (Ch: S, Se) layered superconductor, as a system with local inversion asymmetry, because spin polarisation based on the Rashba–Dresselhaus-type spin–orbit coupling has been observed in centrosymmetric BiCh2-based LaOBiS2 systems, while the BiCh2 layer lacks local inversion symmetry. Herein, we report the existence of extremely high in-plane upper critical fields in the BiCh2-based system LaO0.5F0.5BiS2−xSex (x = 0.22 and 0.69). The superconducting states are not completely suppressed by the applied magnetic fields with strengths up to 55 T. Thus, we consider that the in-plane upper critical field is enhanced by the local inversion symmetry breaking and its layered structure. Our study will open a new pathway for the discovery of superconductors that exhibit a high upper critical field by focusing on the local inversion symmetry breaking.

Tunable and programmable topological valley transport in photonic crystals with liquid crystals

Topological valley transport in photonic crystals (PCs) has attracted great attention owing to its edge modes immune to backscattering. However, flexibly dynamically controlling and reconfiguring the pathway of the topological one-way propagation is still challenging. Here, we propose a tunable and programmable valley PC structure based on nematic liquid crystals (LCs). Inversion symmetry breaking and topological transition are implemented through controlling the relative permittivity of the LC cells. Topological protection of valley edge states and valley-locked beam splitting are demonstrated. Moreover, the LC-based PC can be discretized to a number of supercells, each of which can be coded with “0” or “1”. The wave propagation pathway can be dynamically reconfigured by programming different coding patterns.

(μ-2,2′,2′′,2′′′-{[Pyrazine-2,3,5,6-tetrayltetrakis(methylene)]tetrakis(sulfanediyl)}tetraacetato)bis[aquanickel(II)] heptahydrate

Reaction of the ligand 2,2′,2′′,2′′′-{[pyrazine-2,3,5,6-tetrayltetrakis(methylene)]tetrakis(sulfanediyl)}tetraacetic acid (H4L1), with NiCl2 leads to the formation of a binuclear complex, (μ-2,2′,2′′,2′′′-{[pyrazine-2,3,5,6-tetrayltetrakis(methylene)]tetrakis(sulfanediyl)}tetraacetato-κ5 O,S,N 1,S′,O′:κ5 O′′,S′′,N 4,S′′′,O′′′)bis[aquanickel(II)] heptahydrate, {[Ni2(C16H16N2O8S4)(H2O)2]·7H2O} (I). It crystallizes with two half molecules in the asymmetric unit. The complete molecules are generated by inversion symmetry, with the center of the pyrazine rings being located at crystallographic centres of inversion. The ligand coordinates two NiII ions in a bis-pentadentate manner and the sixfold coordination sphere of each nickel(II) atom (NiS2O3N) is completed by a water molecule. The complex crystallized as a hepta-hydrate. The binuclear complexes are linked by Owater—H...Ocarbonyl hydrogen bonds, forming layers parallel to the (101) plane. This layered structure is additionally stabilized by weak C—H...O hydrogen bonds. Further O—H...O hydrogen bonds involving binuclear complexes and solvent water molecules, together with weak C—H...S hydrogen bonds, link the layers to form a supramolecular framework.

Superconductivity coexisting with ferromagnetism in a quasi-one dimensional non-centrosymmetric (TaSe4)3I

Low-dimensional materials with broken inversion symmetry and strong spin-orbit coupling can give rise to fascinating quantum phases and phase transitions. Here we report coexistence of superconductivity and ferromagnetism below 2.5 K in the quasione dimensional crystals of non-centrosymmetric (TaSe4)3I (space group: P¯421c). The unique phase is a direct consequence of inversion symmetry breaking as the same material also stabilizes in a centro-symmetric structure (space group: P4/mnc) where it behaves like a non-magnetic insulator[1–4]. The coexistence here upfront contradicts the popular belief that superconductivity and ferromagnetism are two apparently antagonistic phenomena. Notably, here, for the first time, we have clearly detected Meissner effect in the superconducting state despite the coexisting ferromagnetic order. The coexistence of superconductivity and ferromagnetism projects non-centrosymmetric (TaSe4)3I as a host for complex ground states of quantum matter including possible unconventional superconductivity with elusive spin-triplet pairing[5–8].

Giant nonlinear Hall effect in twisted bilayer WTe2

In a system with broken inversion symmetry, a second-order nonlinear Hall effect can survive even in the presence of time-reversal symmetry. In this work, we show that a giant nonlinear Hall effect can exist in twisted bilayer WTe2 system. The Berry curvature dipole of twisted bilayer WTe2 (θ = 29.4°) can reach up to ~1400 Å, which is much larger than that in previously reported nonlinear Hall systems. In twisted bilayer WTe2 system, there exist abundant band anticrossings and band inversions around the Fermi level, which brings a complicated distribution of Berry curvature, and leads to the nonlinear Hall signals that exhibit dramatically oscillating behavior in this system. Its large amplitude and high tunability indicate that the twisted bilayer WTe2 can be an excellent platform for studying the nonlinear Hall effect.

Superconductivity in doped Weyl semimetal Mo0.9IR0.1Te2 with broken inversion symmetry

This work presents the emergence of superconductivity in Ir - doped Weyl semimetal T$_d$ - MoTe$_{2}$ with broken inversion symmetry. Chiral anomaly induced planar Hall effect and anisotropic magneto-resistance confirm the topological semimetallic nature of Mo$_{1-x}$Ir$_{x}$Te$_{2}$. Observation of weak anisotropic, moderately coupled type-II superconductivity in T$_d$ -Mo$_{1-x}$Ir$_{x}$Te$_{2}$ makes it a promising candidate for topological superconductor.