Superconducting Tin Selenide/Niobium Diselenide Ferecrystals†

Abstract

X-ray diffraction, electron diffraction and scanning transmission electron microscopy images prove the structurally independent two-dimensional layers of precisely m tin selenide bilayers and a single niobium diselenide trilayer in heterostructure thin films with a rotational disorder between them. The superconducting critical temperatures decrease systematically as m, the number of tin selenide layers, increases. However, all are lower than that known for isolated single niobium diselenide layers. This indicates a decoupling of these layers. A possible mechanism is a decrease in the density of states due to charge donation from the tin selenide layer.

Superconductivity in a misfit layered compound (SnSe)1.16(NbSe2)

“…Similar to MLCs, the ferecrystals are another type layered compounds consisting of same M X and T X 2 layers. The only difference is that the ferecrystals have extensive random rotationally disorder between layers but MLCs do not [18][19][20][21][22]. Therefore the ferecrystals are not in the long-range crystalline state.…”

Tuning metal/superconductor to insulator/superconductor coupling via control of proximity enhancement between NbSe2 monolayers

“…The substrates were glued to chip carriers with silver paste and thin gold wires were attached to the contact pads with small Indium pieces. m [NbSe 2 ] 1 ferecrystals with m = 6, 9, 12, 15, which demonstrate the precision of the layer sequences [29,30]. This precision is confirmed by highangle annular dark-field scanning transmission electron microscopy (HAADF-STEM).…”

“…The synthesis of the ferecrystals allows their structure to be tailored with atomic layer precision [22][23][24][25][26][27]. The technique uses a physical vapor deposition process, followed by annealing step, and is described in detail elsewhere [28,29]. Figure 1(a) gives a sketch to illustrate the layer sequence for the…”

“…] n ferecrystals samples are detailed in [26][27][28][29][30]. The parameter δ indicates the difference of the inplane lattice parameter a between the SnSe and NbSe 2 layers and its values range from 0.157 (m = 1) to 0.136 (m = 9) [26].…”

Unprecedented generation of 3D heterostructures by mechanochemical disassembly and re-ordering of incommensurate metal chalcogenides

“…Due to this structural arrangement, (REX) 1 + x (MX 2 ) are frequently denoted as misfit materials 3,4 , and the presence of chemically and structurally dissimilar 2D fragments in their crystal lattices is responsible for the emergence of intriguing physical properties, including superconductivity 13 , metallicity, semiconductivity 3,14,15 , and diverse magnetism 3,16,17 , among others 4,12,18 . The majority of (REX) 1 + x (MX 2 ) known to date have been synthesized from pure elements, metals, and chalcogens, by heating them in sealed ampules in the presence of halogens or metal halides as transport agents 3,4,[19][20][21] .…”