Spatially separated superconductivity and enhanced charge-density-wave ordering in IrTe2 nano-flake

TL;DR

This study reveals spatial separation of superconductivity and charge-density-wave order in monolayer IrTe2 nano-flakes, demonstrating competition between these states influenced by microstructure and strain effects.

Contribution

First demonstration of monolayer IrTe2 with spatially separated SC and CDW phases using Au-assisted exfoliation and advanced spectroscopy.

Findings

Superconductivity appears at 3.5 K in pure SC regions.

Enhanced TCDW at 605 K in pure CDW regions.

Microstructure and strain influence the competition between SC and CDW.

Abstract

The interplay among various collective electronic states such as superconductivity (SC) and charge density wave (CDW) is of tremendous significance in low-dimensional transition metal dichalcogenides. Thus far, a consensus on the relationship between SC and CDW has not been established in IrTe2, where either competing or collaboration pictures have been suggested in the bulk or thick flakes. Here, we use the state-of-art Au-assisted exfoliation method to overcome the obstacle of interlayer Te-Te bonding, cleaving the IrTe2 down to monolayer for the first time. A striking feature revealed by angle-resolved polarized Raman spectroscopy (ARPRS) and electrical transport measurements is the concurrence of phase separation in one single piece of nano-flake, i.e. the superconducting (P-3m1) and CDW (P-3) area. In the pure SC area, the dimensional fluctuations completely suppress the CDW ordering and induce SC at 3.5 K. Meanwhile, the pure CDW area with much enhanced TCDW at 605 K (compared to TCDW = 280 K in bulk) is always accompanied by a unique wrinkle pattern. Detailed analyses suggest the local strain-induced bond breaking of the Te-Te dimer facilitates the emergence of the CDW order. Our works provide compelling evidence of competition between SC and CDW, highlighting the importance of microstructure in determining the ground states of IrTe2.