Harmonic detection of the Majorana fermion in narrow bandgap InAsSb

非技术摘要：该项目将开发一种替代测量方案，在一种新型混合电容器设备中使用谐波产生，旨在规避传统方法的基本局限性，以解决（仍然悬而未决的）问题：固态"马约拉纳费米子"是否已被发现？这种新的物质状态，理论上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。它的发现和操纵在适当的设计电路可能会导致创建一种新的量子计算机，这是基本上免疫decoherence.Technical摘要：本项目将开发一种测量技术，利用谐波产生在一种新型的混合电容器设备来测量全局密度的低维电子材料的状态，而没有微扰欧姆接触。它的动机是需要明确地识别零偏置隧道传输异常的自旋轨道耦合一维超导体作为可能的签名的预测拓扑电子激发定位到线端点称为"马约拉纳费米子"。简而言之，中间材料的静电电位浮动之间的电容器电极，并可以通过隧道与一个（接地）电极交换电子。在电压V（t）下与顶部电极的电容耦合引起浮置材料与底部接地电极之间的电压降，从而驱动对全局态密度敏感的弹性隧穿。如果驱动频率下的电容性阻抗与特性曲线相当，（电压依赖性）隧道电阻，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，研究团队打算使用高质量的InAsSb来制造纳米线（来自附近的阿德尔菲陆军研究实验室的合作者），其具有比二元组分InAs或InSb中的任一个更低的带隙。该团队将努力确认它也具有较低的有效质量，较高的g因子和较大的自旋轨道相互作用（如k-dot-p理论所预测的那样）。所有这些参数将大大优化马约拉纳形成及其拓扑保护，以提高使用我们的谐波产生测量检测的可能性。

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.