Observation of magnetic quantum phase crossovers in a semiconductor spin ladder

• URL: http://arxiv.org/abs/2608.17789v1
• Date: Tue, 18 Aug 2026 13:50:44 GMT
• Title: Observation of magnetic quantum phase crossovers in a semiconductor spin ladder
• Abstract summary: We realize a programmable Heisenberg spin ladder in a half-filled germanium quantum dot array.<n>Under a fixed magnetic field, we map the rung-singlet, canted antiferromagnetic, and fully polarized phases.<n>Our results establish germanium quantum dot arrays as a controllable platform for quantum magnetism.
• Score: 30.296977335549926
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Understanding collective phases of strongly correlated quantum magnets relies on theoretically tractable model systems with precise microscopic control. Antiferromagnetic spin ladders provide such a setting, hosting field-tunable gapped and gapless phases at half filling and unconventional pairing tendencies upon doping. Here, we realize a programmable Heisenberg spin ladder in a half-filled germanium quantum dot array featuring site-resolved, continuously tunable exchange interactions. Under a fixed magnetic field, we vary the rung and leg coupling to map the rung-singlet, canted antiferromagnetic, and fully polarized phases. Hamiltonian-learning protocols combining equilibrium and dynamical measurements quantitatively characterize the ladder, incorporating spin-orbit interactions to reproduce the observed crossover behavior. Measurements of higher-order spin correlators -- including four-point correlations inaccessible to conventional bulk probes -- reveal signatures of the underlying phase structure despite the finite size. Our results establish germanium quantum dot arrays as a controllable platform for quantum magnetism, opening routes to investigate unconventional superconductivity in doped ladders.

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