Supercurrent and Phase Slips in a Ballistic Carbon Nanotube Bundle Embedded into a van der Waals Heterostructure

Abstract

We demonstrate long-range superconducting correlations in a several-micrometers-long carbon nanotube bundle encapsulated in a van der Waals stack between hBN and NbSe 2 . We show that a substantial supercurrent flows through the nanotube section beneath the NbSe 2 crystal as well as through the 2 μm long section not in contact with it. The large in-plane critical magnetic field of this supercurrent is an indication that even inside the carbon nanotube Cooper pairs enjoy a degree of paramagnetic protection typical of the parent Ising superconductor. As expected for superconductors of nanoscopic cross section, the currentinduced breakdown of superconductivity is characterized by resistance steps due to the nucleation of phase slip centers. All elements of our hybrid device are active building blocks of several recently proposed setups for realization of Majorana fermions in carbon nanotubes.

Supercurrent diode effect and magnetochiral anisotropy in few-layer NbSe2

“…The parity of the layer number N and the lattice orientation is determined, a posteriori , by second harmonic generation (SHG) measurements for all samples. NbSe 2 crystals are fully encapsulated in hBN 30 and edge contacts are fabricated by electron beam lithography 31 . A 250 nm-long channel of 250 nm width is patterned by electron beam lithography and reactive ion etching.…”

“…The dashed white contour highlights the NbSe 2 crystal. Electrodes are fabricated by edge contact techniques 27 , 31 , 47 , while the constrictions are made by reactive ion etching. The yellow arrow indicates the supercurrent pathway.…”

Nanomaterials for Quantum Information Science and Engineering

“…[ 386 ] Bäuml et al have since demonstrated supercurrent and phase slips in a bundle of CNTs encapsulated by h‐BN and 2D NbSe 2 . [ 387 ] These recent results indicate promise for CNTs in superconductor–semiconductor hybrid devices and—potentially—also for confirming presence of Majorana states in devices.…”

“…Recently, Desjardins et al used a proximal ferromagnetic multilayer to enhance spin-orbit coupling in a CNT contacted by superconducting electrodes; they observed oscillations of sub-gap states with applied magnetic field and a zero-bias peak [385] . Bäuml et al have since demonstrated supercurrent and phase slips in a bundle of CNTs encapsulated by h-BN and 2D NbSe2 [386] . These recent results indicate promise for CNTs in superconductor-semiconductor hybrid devices and -potentially -also for confirming presence of Majorana states in devices.…”

Phase slip from weak links formed in artificially-stacked NbSe2

“…Phase slip has been observed in exfoliated NbSe 2 layers [27,28], a 2D Ising superconductor with a critical temperature of T C = 7 K [29,30], by DC measurement and by RF radiation assisted Josephson junction like Shapiro steps. In former studies, uncontrollable disorders in a NbSe 2 layer [27,28] or its junction with a different material [31] have contributed to the phase slip events. It still remains an issue how to use an artificially-stacked homojunction of 2D superconductors to manipulate the order parameter and its topological fluctuation for superconducting quantum device applications.…”