Harmonic detection of the Majorana fermion in narrow bandgap InAsSb

本项目将开发一种替代测量方案，利用新型混合电容器装置中的谐波产生，旨在绕过传统方法的基本限制，解决（仍然开放的）问题：固态“马约拉纳费米子”是否被看到？这种物质的新状态，理论上被预测具有不寻常的行为，是由某些半导体结构中的超导性和电子相互作用引起的。它的发现和在适当设计的电路中的操作可能会导致一种新型量子计算机的产生，这种计算机基本上不受退相干的影响。技术摘要：本项目将开发一种利用新型混合电容器件谐波产生的测量技术，以测量低维电子材料无微扰欧姆接触的整体态密度。它的动机是需要明确地识别自旋轨道耦合一维超导体中的零偏压隧道输运异常，作为定位于称为“马约拉纳费米子”的线端点的预测拓扑电子激发的可能特征。简而言之，中间材料的静电电位漂浮在电容器电极之间，并可以通过隧道与一个（接地）电极交换电子。在电压V(t)处与上电极的电容耦合在浮体材料和底接地电极之间产生电压降，驱动对全局态密度敏感的弹性隧穿。如果驱动频率处的容性阻抗与特性（电压相关）隧道电阻相当，则非线性电导谱分量将被编码到器件的高次谐波响应中。重要的是，研究小组打算使用高质量的InAsSb（来自附近Adelphi陆军研究实验室的合作者）制造纳米线，它比二元成分InAs或InSb具有更低的带隙。该团队将努力确认它也具有更低的有效质量，更高的g因子和更大的自旋轨道相互作用（正如k点p理论所预测的那样）。所有这些参数将大大优化Majorana地层及其拓扑保护，以提高使用我们的谐波产生测量进行检测的可能性。

Non-Technical Abstract:This project will develop an alternative measurement scheme using harmonic generation in a novel hybrid capacitor device aimed to circumvent the fundamental limitations of conventional methods to settle the (still open) question: Has the solid-state "Majorana fermion¨ been seen? This novel state of matter, theoretically predicted to have unusual behaviors, is induced by superconductivity and electron interactions in certain semiconductor structures. Its discovery and manipulation in appropriately-design circuits could lead to the creation of a new kind of quantum computer which is essentially immune to decoherence.Technical Abstract:This project will develop a measurement technique utilizing harmonic generation in a novel hybrid capacitor device to measure global density of states of a low-dimensional electronic material without perturbative ohmic contact. It is motivated by a need to definitively identify zero-bias tunnel-transport anomalies in spin-orbit-coupled one-dimensional superconductors as possible signatures of a predicted topological electronic excitation localized to wire endpoints called the "Majorana fermion¨.Briefly, the electrostatic potential of an intermediate material floats between the capacitor electrodes, and can exchange electrons with one (grounded) electrode via tunneling. Capacitive coupling to the top electrode at voltage V(t) induces a voltage drop between the floating material and the bottom grounded electrode, driving elastic tunneling which is sensitive to the global density of states. If the capacitive impedance at the driving frequency is comparable to the characteristic (voltage-dependent) tunnel resistance, the nonlinear conductance spectrum components will be encoded into the higher harmonic response of the device.Importantly, the research team intends to fabricate the nanowires using high-quality InAsSb (from collaborators at nearby Adelphi Army Research Laboratory), which has a lower bandgap than either of the binary constituents InAs or InSb. The team will work toward confirming that it also has a lower effective mass, higher g-factor, and larger spin-orbit interaction (as predicted by k-dot-p theory. All of these parameters will substantially optimize the Majorana formation and its topological protection to enhance the possibility of detection using our harmonic generation measurement.