A new layer‐structured nitride superconductor. Lithium‐intercalated β‐zirconium nitride chloride, Li_xZrNCl

Abstract

Communications cut-off filters (RG 610 nm for PtOEP, OG 590 nm for [Ru(4,,]CI2) were placed in front of a liquid-nitrogen cooled CCD detector (Model LN/CCD, Princeton Instruments, Inc.), with 578 x 384 pixels in a cell size of 13.25 x 8.83 mm'. Luminescent light from the sample surface was collected with a camera lens (Nikon, 55 mm, 1:1.2) and an imaged formed on the CCD camera. The pressure of the sample chamber was measured using a pressure gauge (Model FA 233, Wallace & Tiernan) with an accuracy of 5 0.1 psi.Trichloroethane was used as the solvent to dissolve the dyes and the polymer 3. The dye concentration in the polymer matrixes ranged from 10 to 1000 ppm. Solutions containing the dye and polymer were spray coated onto the surface of interest. Some of the surfaces were precoated with an epoxy primer of a two-part system based on Super One-Coatm White D3400 and Glass Activator D3498 supplied by Pratt & Lambert. The dye film itself was very thin (between 5 and 15 pm) except for the measurements shown in [*] Prof.

A new intermediate intercalate in superconducting sodium-doped hafnium nitride chloride

“…The relative proportions of the different phases affects the observed critical temperature as well as the superconducting fraction. Samples containing the new stage 2 phase as the only sodium intercalated phase showed bulk superconductivity with a critical temperature of 20 K whereas the samples containing the stage 1 phase in different proportions showed a higher critical temperature, typically 23 K. These results agree with the expected correlation between T c and the doping level in this system and account for the different critical temperatures previously observed, 2 …”

“…[1][2][3]5,7 For sodium intercalated hafnium nitride chloride a superconducting phase has been reported with critical temperatures of 20, 23 or 24 K 8-11 and in lithium intercalated HfNCl, critical temperatures of 18, 20, 24 and 26 K have been observed in different samples showing in some cases co-intercalated organic molecules. 2,12,13 In both systems as well as in doped zirconium nitride chloride that shows lower critical temperatures (close to 12 K), the influence on the critical temperature of factors such as the nature of the transition metal, the co-intercalated molecules and the doping level have still not been completely understood. The crystal structure of Na x HfNCl with x 5 0.29 has been reported as isotypic to YOF with space group R3m and crystal parameters a 5 3.5892(3) Å and c 5 29.722(3) Å .…”

“…1,2 The pristine compounds MNX (M 5 Zr, Hf; X 5 Cl, Br, I) show two layered polytypes, a and b phases, isotypic to FeOCl and SmSI respectively. 3,[4][5][6] The structure of the b phase can be described as a stacking along the c axis of double layers with composition [X-M-N-N-M-X], separated by a van der Waals gap.…”

Chirald-wave superconductivity in doped graphene

“…Another very interesting honeycomb material family is the layered nitrides β-M NCl (M =Hf, Zr), which become superconducting with carrier doping by Na or Li intercalation [186,187]. They consist of honeycomb M N bilayers alternated with Cl bilayers and exhibit transition temperatures as high as 26 K. Although the pristine materials are band insulators without magnetic ordering, various experimental results, including a weak isotope effect [188,189], have pointed to an unconventional superconducting state.…”

Electric-Field-Induced Superconductivity on an Organic/Oxide Interface

“…The discovery of high-T c cuprate is a great success of chemical doping in developing a new superconductor, and many other superconductors, such as fullerenes, ZrNCl and picene, have also been discovered. [1][2][3][4] However, the charge carrier density obtained by chemical doping is limited by the chemical solubility of impurity atoms and the solubility limit of many materials is conventionally very low. Therefore, to make high-density carrier doping to be above the limit, such as in high-pressure chemical reactions, laser doping and thin film fabrication, exploration of a new method are necessary.…”