Day: September 10, 2010

Channel Saturation and Conductance Quantization in Metal Point Contacts

Friday, September 10, 2010 10:00 am – 11:00 am
Room 610, M&M Building

Harsh Deep Chopra
Laboratory for Quantum Devices, Materials Program
Mechanical & Aerospace Engineering Department
The University at Buffalo, The State University of New York, Buffalo, NY

Abstract

Notwithstanding the discreteness of metallic constrictions, it is shown for the first timethat the finite elasticity of stable, single-atom gold constrictions allows for a continuousand reversible change in conductance, thereby enabling direct observation of channelsaturation and conductance quantization. The observed channel saturation andconductance quantization under strain perturbation is achieved by superposition ofatomic/subatomic-scale oscillations on a retracting/approaching gold tip against a goldsubstrate of a scanning probe. Results also show that conductance histograms, whoseuse is considered de rigueur in analysis, are neither suitable for evaluating the stability ofatomic configurations through peak positions or peak height nor appropriate forassessing conductance quantization. A large number of atomic configurations withsimilar conductance values give rise to peaks in the conductance histogram. Thepositions of the peaks and counts at each peak can be varied by changing the conditionsunder which the histograms are made. Histogram counts below 1Go cannot necessarilybe assumed to arise from single-atom constrictions.

Biography

Harsh Deep Chopra (pronounced as ‘Hersh’) is Professor in Mechanical &Aerospace Engineering Department at SUNY-Buffalo, which hosts the Materials Program.Chopra graduated from the University of Maryland’ Materials Department in December 1993.After postdoctoral experience at NIST and Monash University, he joined SUNY-Buffalo inJanuary 1998. Chopra’s primary research interests are focused on single-atom spintronics;mechanics, electronics, and magnetism in atomic sized systems; magnetic functional material(magnetic shape memory alloys, magnetostrictive materials) in thin films, multilayers, and bulkforms; micromagnetic fractals; transport/thermal properties in small systems.