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

Zheng Sun, Fan Xu+17 more|arXiv (Cornell University)|Mar 17, 2026

Topological Materials and Phenomena0 citations

TL;DR

The paper maps how twist-angle in twisted bilayer MoTe2 drives a progression from valley-polarized fractional topological phases to valley-degenerate superconductivity, linking topology, symmetry breaking, and superconductivity.

ABSTRACT

Moiré 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°-5.78°, 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 moiré hole filling factor νh = 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 νh = 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°, 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 moiré systems.

Motivation & Objective

• Investigate how twist angle in twisted bilayer MoTe2 (tMoTe2) affects correlated topological and superconducting phases.
• Identify the evolution from fractional quantum anomalous Hall states to superconductivity as angle increases.
• Examine competition between valley polarization, symmetry breaking, and superconducting tendencies across angles.

Proposed method

• Systematic transport measurements across twist angles from 3.8° to 5.78° in tMoTe2.
• Live characterization of fractional topological states and FQAH effects in partially-filled Chern bands.
• Analysis of moiré filling factors, including νh = 1/2 and νh = 1, to map phase boundaries.
• Comparison of observed phase evolution with known behavior in related moiré systems such as tWSe2.

Experimental results

Research questions

• RQ1 How do fractional topological phases in tMoTe2 evolve as the twist angle increases from small to larger values?
• RQ2 What mechanisms drive the transition from valley-polarized topological states to valley-degenerate superconductivity?
• RQ3 How do filling factors νh = 1/2 and νh = 1 relate to the observed phases across angles?
• RQ4 What is the role of symmetry breaking, magnetic order, and displacement field in stabilizing or suppressing these phases?

Key findings

• At smaller twist angles, partially-filled Chern bands host FQAH states following the Jain sequence.
• An anomalous composite Fermi liquid is observed at moiré hole filling factor νh = 1/2.
• Increasing twist angle suppresses fractional topological phases and reconstructs the half-filled Chern band into symmetry-breaking integer Chern insulators.
• At νh = 1, a transition occurs from robust IQAH insulators to displacement-field-tuned, topologically trivial correlated insulators as angle grows.
• At a twist angle of 5.78°, superconductivity emerges adjacent to the correlated insulating phase, resembling behavior in tWSe2.
• The results suggest a unified twist-angle-driven evolution linking fractional topology, symmetry breaking, magnetic order, and superconductivity.