Quasi-two-dimensional superconductivity from dimerization of atomically ordered AuTe₂Se_4/3 cubes.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Phenomena

Background:

• Emergent phenomena like superconductivity and topological phase transitions are typically observed in strictly two-dimensional (2D) crystalline materials.
• Most bulky layered compounds, despite exhibiting 2D characteristics, do not display these remarkable properties.

Purpose of the Study:

• To investigate the potential for emergent phenomena in bulky materials by inducing dimensionality reduction.
• To report the discovery and characterization of quasi-2D superconductivity in a novel bulk compound, AuTe2Se4/3.

Main Methods:

• Atomic-resolution imaging to analyze crystal structure and identify key bonding.
• Superconductivity measurements at low temperatures (2.85 K).
• Analysis of topological transitions, specifically the Berezinsky-Kosterlitz-Thouless transition, to explain observed superconductivity.

Main Results:

• Discovery of quasi-2D superconductivity in bulk AuTe2Se4/3 at 2.85 K.
• Identification of elongated covalent Te-Te bonds (3.18 and 3.28 Å) responsible for the effective reduction in dimensionality.
• Unraveling the superconductivity's quasi-2D nature through the Berezinsky-Kosterlitz-Thouless topological transition.
• Observation of nesting Fermi sheets potentially enhancing electron-phonon coupling.

Conclusions:

• The bulk material AuTe2Se4/3 exhibits quasi-2D superconductivity, challenging the notion that such phenomena are exclusive to strictly 2D materials.
• The observed superconductivity is attributed to a topological transition, highlighting the role of dimensionality reduction induced by specific chemical bonds.
• Further thinning of the material is proposed as a route to potentially observe more topological phenomena.