Atomic-scale Control of Tunnel Coupling

Xiqiao Wang; Jonathan Wyrick; Ranjit V. Kashid; Pradeep Namboodiri; Scott W. Schmucker; Andrew Murphy; M. D. Stewart, Jr.; Neil Zimmerman; Richard M. Silver

arXiv · 1905.00132

Atomic-scale Control of Tunnel Coupling

Xiqiao Wang·Jonathan Wyrick·Ranjit V. Kashid·Pradeep Namboodiri·Scott W. Schmucker·Andrew Murphy·M. D. Stewart, Jr.·Neil Zimmerman·Richard M. Silver

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Abstract

Atomically precise donor-based quantum devices are a promising candidate for scalable solid-state quantum computing. Atomically precise design and implementation of the tunnel coupling in these devices is essential to realize gate-tunable exchange coupling, and electron spin initialization and readout. Current efforts in atomically precise lithography have enabled deterministic placement of single dopant atoms into the Si lattice with sub-nm precision. However, critical challenges in atomically precise fabrication have meant systematic, atomic-scale control of the tunneling coupling has not been demonstrated. Here using a room-temperature grown locking layer and precise control over the entire atomic-scale fabrication process, we demonstrate atomic-scale control of the tunnel coupling in atomically precise single-electron transistors (SETs). Using the naturally occurring Si (100) 2x1 surface reconstruction lattice as an atomically-precise ruler, we systematically vary the number of lattice counts within the tunnel junction gaps and demonstrate exponential scaling of the tunneling resistance at the atomic limit. Using low-temperature transport measurements, we characterize the tunnel coupling asymmetry in a pair of nominally identical tunnel gaps that results from atomic-scale variation in the tunnel junction and show a resistance difference of four that corresponds to half a dimer row pitch difference in the effective tunnel gap distances - the intrinsic limit of hydrogen lithography precision on Si (100) 2x1 surfaces. Our results demonstrate the key capability to do atom-scale design and engineering of the tunnel coupling necessary for solid-state quantum computing and analog quantum simulation.

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Xiqiao Wang, Jonathan Wyrick, Ranjit V. Kashid, Pradeep Namboodiri, Scott W. Schmucker, Andrew Murphy, M. D. Stewart, Jr., Neil Zimmerman, Richard M. Silver. 2019-07-27. Atomic-scale Control of Tunnel Coupling. https://arxiv.org/abs/1905.00132

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