Ballistic superconductivity in semiconductor nanowires

Abstract

Semiconductor nanowires have opened new research avenues in quantum transport owing to their confined geometry and electrostatic tunability. They have offered an exceptional testbed for superconductivity, leading to the realization of hybrid systems combining the macroscopic quantum properties of superconductors with the possibility to control charges down to a single electron. These advances brought semiconductor nanowires to the forefront of efforts to realize topological superconductivity and Majorana modes. A prime challenge to benefit from the topological properties of Majoranas is to reduce the disorder in hybrid nanowire devices. Here we show ballistic superconductivity in InSb semiconductor nanowires. Our structural and chemical analyses demonstrate a high-quality interface between the nanowire and a NbTiN superconductor that enables ballistic transport. This is manifested by a quantized conductance for normal carriers, a strongly enhanced conductance for Andreev-reflecting carriers, and an induced hard gap with a significantly reduced density of states. These results pave the way for disorder-free Majorana devices.

Approximating the Sachdev-Ye-Kitaev model with Majorana wires

“…We instead envision a realization [ Fig. 1(a)] that exploits Majorana zero modes germinated in proximitized semiconductor nanowires [41,42]-a leading experimental architecture for topological quantum information applications [5][6][7][8][9]11,[13][14][15].…”

“…Majorana fermions provide building blocks for many novel phenomena. As one notable example, Majorana-fermion zero modes [1,2] capture the essence of non-Abelian statistics and topological quantum computation [3,4], and correspondingly now form the centerpiece of a vibrant experimental effort [5][6][7][8][9][10][11][12][13][14][15][16]. More recently, randomly interacting Majorana fermions governed by the "Sachdev-YeKitaev (SYK) model" [17][18][19] were shown to exhibit sharp connections to chaos, quantum-information scrambling, and black holes-naturally igniting broad interdisciplinary activity (see, e.g., [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]).…”

Universal Geometric Path to a Robust Majorana Magic Gate

“…Furthermore, he outlined how one would try to realize the simplest of these non-Abelian states, Majorana zeroenergy bound states (Majoranas for short), in a solid-state system. Since then, much activity has been dedicated to realizing Majoranas in quantum Hall states as well as quantum wells in proximity to superconductors, both theoretically [3][4][5][6][7][8][9] and experimentally [10][11][12][13][14][15][16][17], with significant recent success. Moreover, the experimental efforts recently shifted from a mere detection of Majorana signatures to concrete steps towards the realization of platforms that reveal their non-Abelian statistics and allow for quantum information processing via braiding [18,19].…”

Disorder-induced topological transitions in multichannel Majorana wires

“…For example, in InSb nanowires a subband spacing of order 15 meV has been measured [52,53] together with a g factor of 40-58. Zero-bias peaks that might signal Majorana fermions in these works are typically measured at magnetic fields from 0.1 mT to 1 T [22,54] and exceptionally up to 2.5 T. In all of these cases, the Zeeman splitting remains smaller than the level spacing. Hence, one can argue that RSW nanowires are more experimentally relevant than PW nanowires, which require Zeeman splitting to be much larger than level spacing.…”