Spring 2017

Magnetic Interface Anisotropy, Domain Walls, and Skyrmions

Speaker(s): 
Vincent Sokalski
Dates: 
Thursday, February 23, 2017 - 4:30pm to 5:30pm

The recently discovered Dzyaloshinskii-Moriya Interaction (DMI) in thin films has spawned a new direction for magnetism in spintronic application. This phenomenon stabilizes topological magnetic features including skyrmions and chiral domain walls (DWs) that can be manipulated by electric current with unprecedented efficiency. In this talk, I will review consequences of DMI on the structure of “Dzyaloshinskii” DWs and introduce the creep scaling law, which is paramount to describing a range of elastic interfaces including also superconductor flux lines and fluids being...

Understanding Anomalies and Variations in Magnetic Random Access Memory Devices

Speaker(s): 
Eric Evarts
Dates: 
Thursday, January 12, 2017 - 2:30pm to 3:30pm

Spin-transfer torque magnetic random access memory (STT-MRAM) is a scalable, low-power, non-volatile memory structure based on the magnetic tunnel junction (MTJ). In this talk, I will present the common techniques used for characterizing MTJ thin films and devices using ferromagnetic resonance (FMR) and high-speed pulsed switching with a focus on devices with in-plane magnetization, At the nanodevice level, average thin film properties do not reflect the specifics of individual devices, but instead are representative of ensemble measurements of multiple devices. Minor...

Strongly Coupled Multi-Qubit Systems Using Superconducting Quantum Circuits

Speaker(s): 
Rajamani Vijayaraghavan
Dates: 
Thursday, March 23, 2017 - 4:00pm to 5:00pm

Storing and processing information using quantum two level systems (qubits) promises tremendous speed-up for certain computational tasks like finding prime factors and for simulation of quantum systems. Superconducting electronic circuits operating at millikelvin temperatures have emerged as a leading candidate for building such a quantum processor. One key requirement is controlling and manipulating the interactions between multiple qubits. Rather than using single qubit circuits as building blocks, I will introduce a novel three-qubit superconducting device as an...

Space – The ‘Final’ Frontier: Exploring electron dynamics in the spatial dimensions

Speaker(s): 
Prof. Keshav M. Dani
Dates: 
Thursday, January 5, 2017 (All day)

Abstract:  Since the early days of studying electron dynamics in solid state systems, experimental capabilities have taken great strides – from generating ultrafast pulses across wide swaths of the electromagnetic spectrum (THz to X-Rays), to squeezing electron bunches into sub-picosecond packets, to resolving electron dynamics through photoemitted electrons. With these technologies, achieving high temporal resolution, spectral resolution and momentum resolution has become a relatively straightforward process. These technologies also have the potential for high spatial resolution, birthing...

Whispering Galleries and Berry Phase Switches in Circular Graphene Resonators

Speaker(s): 
Joseph Stroscio
Dates: 
Thursday, January 12, 2017 - 4:00pm to 5:00pm

Ballistic propagation and the light-like dispersion of graphene charge carriers make graphene an attractive platform for optics-inspired graphene electronics where gate tunable potentials can control electron refraction and transmission. In analogy to optical wave propagation in lenses, mirrors and metamaterials, gate potentials can be used to create Fabry-Pérot interferometers and a negative index of refraction for Veselago lensing. In circular geometries, gate potentials caninduce whispering gallery modes (WGM), similar to optical and acoustic whispering galleries [1,2...

Paper and Circuits, Only Atoms Thick

Speaker(s): 
Jiwoong Park
Dates: 
Monday, April 10, 2017 - 4:30pm to 5:30pm

2D layered materials are like paper: they can be colored, stitched, stacked, and folded to form integrated devices with atomic thickness. In this talk, I will discuss how different 2D materials can be grown with distinct electrical and optical properties (coloring), how they can be connected laterally to form pattered circuits (stitching), and how their properties can be controlled by the interlayer rotation (twisting). We will then discuss how these atomically thin papers and circuits can be folded to generate active 3D systems.

Structure and Reactivity of Functional Molecules on Surfaces

Speaker(s): 
Reinhard J. Maurer
Dates: 
Thursday, February 9, 2017 - 4:00pm to 5:00pm

Fundamental understanding of molecular structure and chemical reactivity at complex interfaces is key to many technological applications ranging from single molecule electronics to functional surfaces. An important goal of molecular nanotechnology is to manipulate single molecules in well-defined chemical environments. Using electronic structure methods, we study prototypical example systems such as azobenzene [1] and porphyrine [2] derivatives adsorbed on well-defined single crystal metal surfaces. Hereby the focus lies on the effects of molecule functionalization,...

Quantum Entanglement and the Geometry of Spacetime

Speaker(s): 
Matthew Headrick
Dates: 
Monday, February 13, 2017 - 4:30pm to 6:00pm

Recent developments in the study of quantum gravity have revealed a surprising and beautiful connection between quantum entanglement and the geometry of spacetime. This discovery offers a new perspective on old puzzles concerning black holes, and may lead to a profoundly new way of thinking about the emergence of spacetime from fundamental quantum-mechanical building blocks. I will describe these developments, explaining along the way the necessary background in quantum gravity and quantum information theory.

Quantum Control of Spins in Silicon

Speaker(s): 
Mark Eriksson
Dates: 
Monday, April 3, 2017 - 4:30pm to 5:30pm

One of the remarkable features of spins in the solid state is the enormous range of time-scales over which coherent manipulation is possible. If one considers gate-controlled manipulation of nuclear spins at one extreme, and strongly-interacting multi-electron qubits at the other extreme, coherent control of spins in semiconductors has been demonstrated with over 9 orders of magnitude variation in the manipulation time. Remarkably, confining three electrons in two neighboring quantum dots enables all electrical control and measurement of spin dynamics on time scales less...

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