The end of the glory days of transistor scaling has resulted in a worldwide thrust to explore novel device concepts, exotic materials, and revolutionary ways of processing information to sustain the future of computation. Spin degrees of freedom, the fundamental building blocks of magnetism, are actively sought as a medium of information storage and manipulation in both classical and quantum platforms of computing. The success of this emerging spin-electronic technology strongly depends on the ability to engineer properties of the microscopic spins in various solid-state materials. In this talk, I will present an atomistic modeling approach that combines intrinsic material and extrinsic device properties under a unified framework to describe spins and their interactions with the environment. This approach captures important spin properties such as exchange, spin-orbit, hyperfine, and magnetic dipolar interactions from a description of atomic orbitals and chemical bonds, and provides fundamental insights into engineering these interactions at the atomic level.

I will show how this modeling approach has impacted the field of silicon quantum computing. In particular, I will highlight a novel finding of a Dresselhaus-like spin-orbit (SO) coupling at the surface of silicon, and propose an order of magnitude improvement in spin dephasing times based on its anisotropy [1]. I will also discuss modeling guided breakthroughs in donor spin qubits, such as realization of single qubits [2, 3], understanding of STM imaging experiments [4], engineering of very long spin lifetimes [5], and ultimaley the design of all-electrical multi- qubit spin devices. Finally, I will present atomistic quantum transport guided designs of high performance tunnel transistors in 2D materials [6] utilizing their unconventional properties. This material-to-device framework can also be applied to devices of large SO materials and topological insulators without prior knowledge of the types or magnitudes of SO couplings.

Rajib Rahman obtained his PhD degree in Electrical and Computer Engineering from Purdue University in 2009 in the area of computational nanoelectronics. He was a postdoctoral fellow in Sandia National Laboratories in the Silicon Quantum Information Science and Technology group from 2009-2012. Since 2012, he has been employed as a Research Assistant Professor in the Network for Computational Nanotechnology at Purdue. Rajib develops and employs atomistic simulation methods to model nanoscale electronic devices, specializing in the quantum mechanical many-body description of spins and their interactions with the solid-state environment. Rajib collaborates with some leading experimental groups in academia and in national laboratories in the field of semiconductor quantum computing.

1. Ferdous et. al., Interface induced spin-orbit interaction in silicon quantum dots and prospects for scalability, arXiv:1703.03840 (2017).
2. Rahman et. al., High Precision Quantum Control of Single Donor Spins in Silicon, PRL 99, 036403 (2007).
3. Laucht et. al., Electrically controlling single-spin qubits in a continuous microwave field, Sci. Adv. 1, e1500022 (2015).
4. Salfi et. al. Nat. Mat. 13, 650 (2014).
5. Hsueh et. al. PRL 113, 246406 (2014).
6. Ilatikhamaneh et. al., Sci. Rep. 31501 (2016).

Researchers should cite this work as follows:

• Rajib Rahman (2017), "Quantum Spins in the Solid-State: An Atomistic Material-to-Device Modeling Approach," https://nanohub.org/resources/27210.

  BibTex | EndNote

1. nanoelectronics
2. spintronics
3. transistors