BEGIN:VCALENDAR VERSION:2.0 CALSCALE:GREGORIAN PRODID:UW-Madison-Physics-Events BEGIN:VEVENT SEQUENCE:0 UID:UW-Physics-Event-2308 DTSTART:20120323T203000Z DURATION:PT1H0M0S DTSTAMP:20260412T060926Z LAST-MODIFIED:20120321T184029Z LOCATION:2241 Chamberlin Hall (coffee at 4:30 pm) SUMMARY:The quantum and classical properties of spins on surfaces\, Ph ysics Department Colloquium\, Andreas Heinrich\, IBM Almaden Research Lab DESCRIPTION:The scanning tunneling microscope has been an extremely su ccessful experimental tool because of its atomic-scale spatial resolut ion. In recent years this has been combined with the use of low temper atures\, culminating in precise atom manipulation and spectroscopy wit h microvolt energy resolution. A cluster of magnetic atoms on a surfac e behaves similar to a classical magnetic particle: itaEuroTMs magneti zation points along an easy-axis direction in space and magnetization reversal requires sufficient thermal energy to overcome a barrier. In this talk we will discuss how many atoms it takes to create such creat es\, which offers crucial insights into the size limits of stable magn etic nanoparticles. When the number of atoms becomes too small we obse rve quantum tunneling of magnetization aEuro"\; in the present cas e of the aEurooeclassicalaEuro Neel vector. Single atoms that are slig htly decoupled from conducting substrates behave more like quantum mec hanical entities. These can be studied with inelastic tunneling spectr oscopy\, a technique we coined spin-excitation spectroscopy. With this approach it is possible to measure the energy eigenstates of the quan tum spin Hamiltonian that describes spins on surfaces with high precis ion. We will introduce its application to the measurement of the Zeema n energy\, to magneto-crystalline anisotropy\, and to spin-spin coupli ng via a superexchange interaction.
\n
\nDr. Andreas Heinrich Bio
\nAndreas Heinrich leads a research team at IBM's Almaden Rese arch Center focused on exploring atomic-scale structures for possible applications in computation and datastorage. In January 2012 Heinrich and his team presented the worldaEuroTMs smallest magnetic data storag e elements consisting of only 12 magnetic atoms. The work was publishe d in the highest ranking scientific journal\, Science\, and widely rep orted in the media\, including the New York Times. This work was based on a long-term research effort in HeinrichaEuroTMs team that started with the exploration of the magnetic properties of individual magnetic atoms on surfaces over ten years ago\, highlighting IBMaEuroTMs commi tment to long-term\, exploratory research. Heinrich regularly gives in vited lectures and seminars\, including plenary lectures at leading in ternational conferences. His main interest is in the exploration of th e exciting world of atoms and structures built with atomic-scale preci sion and in educating the public on the amazing world of nanoscience. Heinrich is both a scientist and an engineer with a keen interest in a dvancing the experimental capabilities of state-of-the-art research to ols. He and his team recently improved the time resolution of scanning tunneling microscopes aEuro" the mot advanced tool for atomic-scale s tudies on surfaces aEuro" by a factor of 1 million\, another breakthro ugh paper published in Science in 2010. HeinrichaEuroTMs longer-term i nterest lies in the emerging field of quantum computation\, where he h opes to demonstrate the use of single magnetic atoms on surfaces as qu bits. Quantum computation has the potential to vastly improve computat ional performances of computers by taking advantage of the intriguing world of quantum mechanics that governs the properties of atoms. A nat ive of Germany\, Heinrich received his PhD in 1998 from the University of Goettingen in Germany and joined IBM in the same year as a postdoc in Dr. Donald EigleraEuroTMs team. Eigler is world-renowned for being the first person to reproducibly move individual atoms on surfaces\, a tradition carried on proudly in HeinrichaEuroTMs research efforts. URL:https://www.physics.wisc.edu/events/?id=2308 END:VEVENT END:VCALENDAR