Dahlem Center for Complex Quantum Systems and Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany.
Department of Physics, Yale University, New Haven, Connecticut 06520, USA.
Phys Rev Lett. 2015 Dec 31;115(26):266804. doi: 10.1103/PhysRevLett.115.266804. Epub 2015 Dec 29.
Experimental evidence for Majorana bound states largely relies on measurements of the tunneling conductance. While the conductance into a Majorana state is in principle quantized to 2e^{2}/h, observation of this quantization has been elusive, presumably due to temperature broadening in the normal-metal lead. Here, we propose to use a superconducting lead instead, whose gap strongly suppresses thermal excitations. For a wide range of tunneling strengths and temperatures, a Majorana state is then signaled by symmetric conductance peaks at eV=±Δ of a universal height G=(4-π)2e(2)/h. For a superconducting scanning tunneling microscope tip, Majorana states appear as spatial conductance plateaus while the conductance varies with the local wave function for trivial Andreev bound states. We discuss effects of nonresonant (bulk) Andreev reflections and quasiparticle poisoning.
实验证据表明，马约拉纳束缚态在很大程度上依赖于隧穿电导的测量。虽然进入马约拉纳态的电导在原理上是量子化的，为 2e^{2}/h，但由于正常金属引线中的温度展宽，这种量子化很难被观察到。在这里，我们建议使用超导引线来代替，其能隙强烈抑制热激发。对于一个广泛的隧穿强度和温度范围，一个马约拉纳态将由对称的电导峰值在 eV=±Δ处指示，峰值高度为 G=(4-π)2e(2)/h。对于超导扫描隧道显微镜探针，马约拉纳态表现为空间电导平台，而对于平凡的安德烈夫束缚态，电导随局部波函数而变化。我们讨论了非共振（体）安德烈夫反射和准粒子中毒的影响。
