拓扑绝缘体-超导体界面处分数热导的拓扑与动力学起源
Topological and kinetic origins of fractional thermal conductance at the topological insulator--superconductor interface
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中文总结 AI 辅助
该研究证明在完全热化下，手征边缘网络热导仅由反常数据决定，无法区分拓扑与动力学起源，并借助拓扑绝缘体-超导体界面及涡旋分数电荷与噪声测量实现机制分辨。
中文摘要 AI 辅助
Roy等人最近的一项实验（Nat. Commun. 17, 2853 (2026)）在双层石墨烯中的双极（ν,ν'）=(2,-1)结处展示了稳健的半整数热导平台κ₀T/2，该平台并非由非阿贝尔拓扑产生，而是由共传播的电子和空穴边缘模式完全热化所致。我们证明了一个定理，该定理确定了何时能区分这两种起源：在完全热化条件下，由理想浮置接触连接的手征边缘段网络的两端热导是各段净手征中心荷的有理函数，这些量由引力反常固定，且对任意局部边界动力学不变。其推论是一个不可能性陈述：当两个实现在同一网络上呈现相同的反常数据时，任何热导测量都无法区分它们。平衡后的(2,-1)值等于手征马约拉纳模式的中心荷，这是关于一个填充组合的算术事实，但无论这种巧合发生在何处，它都超出了测温术的范畴，区分必须来自电荷扇区，而电荷扇区在超导边界处不受反常固定。我们将拓扑绝缘体-超导体界面作为应用加以发展：涡旋携带来自θ=π磁电耦合的分数电荷e/4，边界承载中心荷为1/2的手征马约拉纳模式，而横向相邻的整数量子霍尔（IQH）区域提供了动力学实现。洛伦兹比（对于孤立马约拉纳边界是反常的，在复合器件中为L₀/(1+4|ν_IQH|)）和过剩散粒噪声（随B从e/4涡旋隧穿增长，而对IQH平台锁定）共同解析了该机制，前提是量子霍尔边缘不紧邻超导体。
英文摘要
A recent experiment by Roy et al. (Nat. Commun. 17, 2853 (2026)) demonstrated a robust half-integer thermal conductance plateau, κ_0 T/2, at a bipolar (ν,ν')=(2,-1) junction in bilayer graphene, produced not by non-Abelian topology but by full equilibration of co-propagating electron and hole edge modes. We prove a theorem that fixes when the two origins can be told apart: under full thermal equilibration, the two-terminal thermal conductance of a network of chiral edge segments joined at ideal floating contacts is a rational function of the net chiral central charges of the segments alone, quantities pinned by the gravitational anomaly and invariant under arbitrary local boundary kinetics. The corollary is an impossibility statement: whenever two realizations present the same anomaly data to the same network, no thermal-conductance measurement can distinguish them. That the equilibrated (2,-1) value equals the central charge of a chiral Majorana mode is an arithmetic fact about one filling combination, but wherever such a coincidence occurs it is beyond the reach of thermometry, and the separation must come from the charge sector, which is not anomaly-pinned at a superconducting boundary. We develop the topological insulator-superconductor interface as the application: a vortex carries fractional charge e/4 from the θ= πmagnetoelectric coupling, the boundary hosts a chiral Majorana mode of central charge 1/2, and a laterally adjacent integer quantum Hall (IQH) region supplies the kinetic realization. The Lorenz ratio (anomalous for the isolated Majorana boundary, L_0 / (1 + 4|ν_{IQH}|) in the composite device) and the excess shot noise (growing with B from e/4 vortex tunneling versus locked to IQH plateaus) together resolve the mechanism, provided the quantum Hall edge does not abut the superconductor.
发表机构
- Universidad Nacional Autónoma de México（墨西哥国立自治大学）
- University of Zurich（苏黎世大学）
- Pontificia Universidad Católica Argentina（阿根廷天主教大学）
- Comisión Nacional de Energía Atómica（国家原子能委员会）
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