Twist-angle evolution from valley-polarized fractional topological phases to valley-degenerate superconductivity in twisted bilayer MoTe2

TL;DR

This study systematically explores how twist angle influences the emergence of fractional topological phases, symmetry-breaking states, and superconductivity in twisted bilayer MoTe2, revealing a continuous evolution of quantum phases.

Contribution

It provides the first comprehensive phase diagram of tMoTe2 across a range of twist angles, showing the transition from fractional topological states to superconductivity.

Findings

Fractional quantum anomalous Hall states at small twist angles.

Suppression of fractional phases with increasing twist angle.

Emergence of superconductivity near 5.78° twist angle.

Abstract

Moir\'e superlattices formed by semiconducting transition metal dichalcogenides (TMDs) provide a highly tunable platform for investigating strongly correlated and topological quantum phases. As a prototypical example, twisted bilayer MoTe2 (tMoTe2) has been shown to host fractional topological phases, such as zero-field fractional Chern insulators (FCIs) exhibiting fractional quantum anomalous Hall (FQAH) effects. However, how these correlated topological phases evolve with twist angle and compete with other quantum phases in tMoTe2 remains largely unexplored. Here we report a systematic transport study of twist-angle-dependent phase diagrams in tMoTe2 across a range of 3.8{\deg}-5.78{\deg}, revealing an evolution from fractionalized states of matter with spontaneous valley polarization to valley-degenerate superconductivity. At relatively small twist angles, partially-filled Chern bands of tMoTe2 host FQAH states following the Jain sequence, together with signatures of an anomalous composite Fermi liquid at moir\'e hole filling factor {\nu}h = 1/2. Increasing twist angle progressively suppresses fractional topological phases and reconstructs the half-filled Chern band into symmetry-breaking integer Chern insulating states. At {\nu}h = 1, we observe a transition from robust integer quantum anomalous Hall (IQAH) insulators at small angles to displacement-field-tuned, topologically trivial correlated insulators at larger angles. Remarkably, at a twist angle of 5.78{\deg}, superconductivity emerges adjacent to the correlated insulating phase, with a phase diagram closely resembling that recently reported in twisted bilayer WSe2 (tWSe2). Our results uncover a unified twist-angle-driven phase evolution linking fractional topology, symmetry breaking, magnetic order, and superconductivity, providing new insight into the emergent quantum phenomena in moir\'e systems.