Metal-Insulator Transition and Emergent Gapped Phase in the Surface-Doped 2D Semiconductor 2H-MoTe$_2$

TL;DR

This study reveals a metal-insulator transition and emergent gapped phase in surface-doped 2H-MoTe$_2$, driven by strong electron-phonon interactions and disorder, indicating potential for polaronic insulators and high-temperature superconductivity.

Contribution

It demonstrates that alkali-metal deposition can effectively enhance many-body interactions in 2D semiconductors, leading to new quantum phases in 2H-MoTe$_2$.

Findings

Observation of a metal-insulator transition in surface-doped 2H-MoTe$_2$

Detection of strong electron-phonon coupling via replica bands

Identification of a potential polaronic insulator or superconductor phase

Abstract

Artificially created two-dimensional (2D) interfaces or structures are ideal for seeking exotic phase transitions due to their highly tunable carrier density and interfacially enhanced many-body interactions. Here, we report the discovery of a metal-insulator transition (MIT) and an emergent gapped phase in the metal-semiconductor interface that is created in 2H-MoTe$_2$ via alkali-metal deposition. Using angle-resolved photoemission spectroscopy, we found that the electron-phonon coupling is strong at the interface as characterized by a clear observation of replica shake-off bands. Such strong electron-phonon coupling interplays with disorder scattering, leading to an Anderson localization of polarons which could explain the MIT. The domelike emergent gapped phase could then be attributed to a polaron extended state or phonon-mediated superconductivity. Our results demonstrate the capability of alkali-metal deposition as an effective method to enhance the many-body interactions in 2D semiconductors. The surface-doped 2H-MoTe$_2$ is a promising candidate for realizing polaronic insulator and high-$T_c$ superconductivity.