Quasi-two-dimensional superconductivity from dimerization of atomically ordered AuTe2Se4/3 cubes

Abstract

The emergent phenomena such as superconductivity and topological phase transitions can be observed in strict two-dimensional (2D) crystalline matters. Artificial interfaces and one atomic thickness layers are typical 2D materials of this kind. Although having 2D characters, most bulky layered compounds, however, do not possess these striking properties. Here, we report quasi-2D superconductivity in bulky AuTe2Se4/3, where the reduction in dimensionality is achieved through inducing the elongated covalent Te–Te bonds. The atomic-resolution images reveal that the Au, Te, and Se are atomically ordered in a cube, among which are Te–Te bonds of 3.18 and 3.28 Å. The superconductivity at 2.85 K is discovered, which is unraveled to be the quasi-2D nature owing to the Berezinsky–Kosterlitz–Thouless topological transition. The nesting of nearly parallel Fermi sheets could give rise to strong electron–phonon coupling. It is proposed that further depleting the thickness could result in more topologically-related phenomena.

Berezinskii-Kosterlitz-Thouless transition in the type-I Weyl semimetal PtBi$_2$

“…Remarkably, we show that the superconductivity persists in a 60 nm thin exfoliated sample in which its 2D nature is evidenced and for which a Berezinsky-Kosterlitz-Thouless (BKT) transition takes place. To our knowledge, and excluding the case of effective 2D layered superconductors 58,59 , the flake is five times thicker than any superconducting films exhibiting a BKT transition reported so far 60 , making PtBi 2 a prime candidate to study low dimensional superconductivity. Among the few Weyl semimetals showing a superconducting transition under ambiant pressure [61][62][63][64][65] , PtBi 2 is, together with MoTe 2 66 , the only one exhibiting such a 2D superconductivity.…”

Ultrafast photonics of two dimensional AuTe2Se4/3 in fiber lasers

“…2c displays the high resolution TEM (HRTEM) image, and the corresponding selected-area electron diffraction (SAED) pattern is presented. The atomic intra-spacing of two perpendicular direct is about 2.8 Å, which corresponds to the interlayer spacing of (310) or (031) plane 29 . The chemical composition is further investigated by x-ray photoelectron spectroscopy (XPS).…”

“…Recently, a new 2D material AuTe 2 Se 4/3 has been successfully prepared by Guo et al 29 . Through the introduction of Se element, they have successfully transformed the three-dimensional disordered cubic AuTe 2 phase into a 2D layered structure, and have proved that the 2D state of AuTe 2 Se 4/3 comes from the Berezinsky-Kosterlitz-Thouless topological transition.…”

Bereziskii-Kosterlitz-Thouless transition in the Weyl system PtBi2

“…Remarkably, we show that the superconductivity persists in a 60 nm thin exfoliated sample in which its 2D nature is evidenced and for which a Berezinsky-Kosterlitz-Thouless (BKT) transition takes place. To our knowledge, and excluding the case of effective 2D layered superconductors 58,59 , the flake is five times thicker than any superconducting films exhibiting a BKT transition reported so far 60 , making PtBi2 a prime candidate to study low dimensional superconductivity. Among the few Weyl semimetals showing a superconducting transition under ambient pressure [61][62][63][64][65] , PtBi2 is, together with MoTe2 66 , the only one exhibiting such a 2D superconductivity.…”