区分拓扑马约拉纳线与普通线段的量子电容特征
Distinguishing Quantum Capacitance Signatures of a Topological Majorana Wire from a Normal Wire Segment
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- Clemson University（克莱姆森大学）
- University of Maryland（马里兰大学）
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中文总结 AI 辅助
本研究通过分析量子电容响应在独立控制参数范围内的持续性，区分了拓扑马约拉纳线与无隙普通线段的类马约拉纳量子电容响应机制。
中文摘要 AI 辅助
马约拉纳零能模（MZMs）是预期出现在拓扑超导（TS）线端点的空间分离近零能激发。量子点干涉仪可用于探测TS线的量子电容，电容共振的位置和幅度提供MZMs的相关信息，而其磁通量依赖性则探测与两个马约拉纳模的相干耦合。近期研究表明，无隙（即Δ=0）线段也可通过阿哈罗诺夫-玻姆干涉呈现磁通量依赖的量子电容振荡，经适当调控可重现类马约拉纳响应。本文证明这两种机制可通过实验区分：在无隙普通线段中，两个依赖宇称的信号源于对应普遍零能态缺失的独立能量共振；相比之下，拓扑线中具有偶、奇宇称的一对低能能级在能量上近简并，因此两个宇称分支在量子点势中仍处于同一较宽共振区域内，且在量子点势和线化学势的独立变化下持续存在。研究结果表明，实验观测到的量子电容响应并非由参数空间某一优化点的特定磁通量轨迹区分，而是由其在包括量子点势在内的有限范围独立控制参数下的持续性所区分。这种参数空间稳定性提供了直接手段，可排除无隙普通线段作为观测到的类马约拉纳响应的起源。
英文摘要
Majorana zero modes (MZMs) are spatially separated, near-zero-energy excitations expected at the ends of a topological superconducting (TS) wire. A quantum-dot interferometer can be used to probe the quantum capacitance of the TS wire, and the location and magnitude of the capacitance resonances provide information about the MZMs, while their magnetic flux dependence probes coherent coupling to the two Majorana modes. It has been recently shown that, a gapless (i.e., $Δ=0$) wire segment can also exhibit flux-dependent quantum capacitance oscillations through Aharonov-Bohm interference and, with suitable tuning, can reproduce a Majorana-like response. Here we show that the two mechanisms can be distinguished experimentally. In the gapless normal wire segment, the two parity-dependent signals originate from separate energy resonances corresponding to the lack of generic zero-energy states. By contrast, in the topological wire, the pair of low energy levels with even and odd parity are nearly degenerate in energy, and therefore, the two parity branches remain within the same broader resonance region in the quantum-dot potential, and persist under independent variations of the dot potential and wire chemical potential. Our results show that the experimentally observed quantum capacitance response is distinguished not by a particular flux trace at one optimized point in parameter space, but by its persistence over a finite range of independently controlled parameters, including the quantum-dot potential. This parameter space stability provides a direct means of ruling out the gapless normal wire segment as the origin of the observed Majorana-like response.
