Canadian Institute for Advanced Research

Canadian Institute for Advanced Research
Quantum Materials Program Presentation to the 15-year Review Panel of the Canadian Institute for Advanced Research by Louis Taillefer, Director of Superconductivity Program. 17 October 2003

Superconductivity A century of electron physics
1957 1957 BCS theory of superconductivity BCS theory of superconductivity 1911 1911 Discovery of superconductivity Discovery of superconductivity 1980 Electrons in matter are fundamentally understood … 1956 1956 Landau’s Fermi-liquid theory 1897 1897 “Discovery” of the electron “Discovery” of the electron

Superconductivity ? 1986 Discovery of superconductivity in cuprates

Superconductivity ? 1988 – CIAR Superconductivity Program
1987 – Nobel Prize in Physics 1987 – “Woodstock of Physics” A SCIENTIFIC REVOLUTION

Superconductivity Program 1988 UBC The Program currently consists of 29 Canadian members: 22 Associates, 6 Scholars and one Fellow, the Director. Associates and Scholars are treated alike and the CIAR provides partial teaching release to all who need it. Right from the inception, the decision was taken not to appoint Fellows with full teaching release in general but to distribute partial release to a larger group of Program members. This rather unique approach within CIAR proved successful in that it multiplied by more than five the number of university researchers who could benefit from the very real advantage of a reduced teaching load (typically brought down to a level that is comparable with that encountered in leading American universities). This created a critical mass of dedicated experts that could then be competitive with the large research centres leading the field of high-temperature superconductivity. The Program also includes nine Foreign Associates and one Fellow (Ian Affleck, at Boston University since July 2001) in the US, Japan and Europe. Sherbrooke McMaster

Quantum Materials Program 2003 Alberta UBC NRC 30 in Canada 9 abroad Waterloo Sherbrooke SFU McMaster Toronto

Canadian Members University of British Columbia Ian Affleck Doug Bonn
Jess Brewer Marcel Franz Walter Hardy Rob Kiefl Ruixing Liang George Sawatzky Philip Stamp University of Alberta Frank Marsiglio Simon Fraser University Steven Dodge Jeff Sonier University of Toronto Robert Birgeneau Hae-Young Kee Yong Baek Kim Michael Walker John Wei McMaster University John Berlinsky Jules Carbotte Bruce Gaulin Catherine Kallin Graeme Luke John Preston Tom Timusk University of Sherbrooke Claude Bourbonnais Patrick Fournier Louis Taillefer André-Marie Tremblay NRC – Chalk River William Buyers University of Waterloo Michel Gingras appointed since 1998 Our appointment strategy since 1998 was guided by the following principles: assist Canadian universities in recruiting top candidates to faculty positions rapidly strengthen the foreign component of the Program broaden the range of expertise and fields of research Since 1998 we have appointed nine Canadian Associates and six Scholars at six Canadian universities, with a whole array of new expertise – frustrated magnetism, quantum Hall effect, ruthenates, manganites, thin films, scanning tunneling spectroscopy, synchrotron x-ray scattering, etc. All six Scholars (Steven Dodge and Jeff Sonier at SFU, Patrick Fournier at Sherbrooke, Hae-Young Kee and John Wei at Toronto, and Marcel Franz at UBC) were appointed in the last three years, and it is fair to say that four of them would not have come to Canada had it not been for CIAR involvement.

Canadian Members Theory Experiment University of British Columbia
Ian Affleck Doug Bonn Jess Brewer Marcel Franz Walter Hardy Rob Kiefl Ruixing Liang George Sawatzky Philip Stamp University of Alberta Frank Marsiglio Simon Fraser University Steven Dodge Jeff Sonier University of Toronto Robert Birgeneau Hae-Young Kee Yong Baek Kim Michael Walker John Wei McMaster University John Berlinsky Jules Carbotte Bruce Gaulin Catherine Kallin Graeme Luke John Preston Tom Timusk University of Sherbrooke Claude Bourbonnais Patrick Fournier Louis Taillefer André-Marie Tremblay NRC – Chalk River William Buyers University of Waterloo Michel Gingras Theory Experiment

Canadian Members Theory Experiment Materials
University of British Columbia Ian Affleck Doug Bonn Jess Brewer Marcel Franz Walter Hardy Rob Kiefl Ruixing Liang George Sawatzky Philip Stamp University of Alberta Frank Marsiglio Simon Fraser University Steven Dodge Jeff Sonier University of Toronto Robert Birgeneau Hae-Young Kee Yong Baek Kim Michael Walker John Wei McMaster University John Berlinsky Jules Carbotte Bruce Gaulin Catherine Kallin Graeme Luke John Preston Tom Timusk University of Sherbrooke Claude Bourbonnais Patrick Fournier Louis Taillefer André-Marie Tremblay NRC – Chalk River William Buyers University of Waterloo Michel Gingras Theory Experiment Materials

Foreign Members Université de Paris Denis Jérome Kyoto University
Yoshiteru Maeno Columbia University Andrew Millis Stanford University Kathryn Moler Robert Laughlin Spallation Neutron Source, Oak Ridge Thom Mason University of California – Los Angeles Steve Kivelson Florida State University Zachary Fisk Princeton University Philip Anderson In 1998 we took a fresh look at foreign membership and decided to keep only Denis Jérome at the University of Paris and his highly productive collaboration with Claude Bourbonnais on organic conductors. We wanted not only to attract international leaders covering the full gamut of theoretical, experimental and materials expertise in a broad range of areas, but also to enlist their active participation. In this we were remarkably successful. We appointed eight new Foreign Associates in two years. Zach Fisk (Florida) and George Sawatzky (then at the University of Groningen in Holland) joined in 1999, bringing top expertise in fields complementary to cuprates, namely heavy fermions and transition-metal oxides. In 2000, another six Associates were appointed outside Canada: Kathryn Moler and Robert Laughlin at Stanford University, Yoshiteru Maeno at Kyoto University, Andrew Millis at Rutgers University, Steve Kivelson at UCLA, and Philip Anderson at Princeton University. Moler is one of the most promising young experimentalists in the field. Maeno is a superb crystal grower and the discoverer of superconductivity in the ruthenates, another family of fascinating oxides. The two Nobel laureates, Anderson and Laughlin, bring to the Program unparalleled expertise on new states of matter. Theorists Kivelson and Millis are leading figures in condensed-matter physics. The sum of new appointments (Canadian and Foreign) represents a dramatic renewal of the Program membership, with 60% of members appointed since the last Program review. In summary, the Superconductivity Program has grown from a small group of ten Canadian researchers sharply focused on cuprates to a broad, much more international network of forty scientists investigating a wide variety of novel materials. It is noteworthy that even with this growth the Program has managed to retain its characteristically strong level of interaction amongst members. appointed since 1998

Yoshiteru Maeno Columbia University Andrew Millis Stanford University Kathryn Moler Robert Laughlin Spallation Neutron Source, Oak Ridge Thom Mason University of California – Los Angeles Steve Kivelson Florida State University Zachary Fisk Princeton University Philip Anderson Theory Experiment

Yoshiteru Maeno Columbia University Andrew Millis Stanford University Kathryn Moler Robert Laughlin Spallation Neutron Source, Oak Ridge Thom Mason University of California – Los Angeles Steve Kivelson Florida State University Zachary Fisk Princeton University Philip Anderson Theory Experiment Materials

Advisory Committee – Vic Emery, Brookhaven National Laboratory (ex-chair)* Alain Caillé, Université de Montréal * Michael Norman, Argonne National Laboratory (chair) Bertram Batlogg, ETH-Zürich and Bell Labs - Lucent Technologies Phuan Ong, Princeton University George Sawatzky, University of British Columbia The Advisory Committee was largely renewed in 1998, with only Vic Emery and Alain Caillé continuing. Three leading experts in the field were appointed: Bertram Batlogg (Bell Labs-Lucent Technologies and ETH-Zurich), Michael Norman (Argonne National Laboratory) and Phuan Ong (Princeton University). All three have taken an active role both in their advisory capacity and as direct contributors to the scientific activities of the Program. After a three-year term, Ong stepped down and George Sawatzky was appointed for a one-year term starting in Norman took over from Emery as Chair last year. * Continuing from previous cycle

Advisory Committee – 2003-2008 Seamus Davis, Cornell University
Rick Greene, University of Maryland Allan MacDonald, University of Texas at Austin

A New World for Electrons
Electrons in Cuprates A New World for Electrons CuO2 plane

High-Temperature Superconductivity
Discoveries New ideas New capabilities New materials High-temperature superconductivity Progress at the fundamental scientific level has been impressive. A host of highly unusual properties have been discovered – for example, d-wave superconductivity, “stripes” and the “pseudogap”. The race to understand high-temperature superconductors has pushed the capabilities of many experimental probes to staggering limits of sensitivity and resolution – for example, in photoemission spectroscopy and scanning tunneling spectroscopy. The ferment on the theory front has been truly remarkable – with proposals for new states of matter, the fractionalization of the electron, the unification of magnetism and superconductivity, and more.

Discoveries PHASE DIAGRAM OF CUPRATES insulator Temperature m a g n e t i s metal superconductor Electron concentration

Discoveries D-wave superconductivity PHASE DIAGRAM OF CUPRATES Hardy, Bonn & Liang ( Berlinsky & Kallin ) insulator Temperature m a g n e t i s metal superconductor Electron concentration

Discoveries D-wave superconductivity PHASE DIAGRAM OF CUPRATES Pseudogap Timusk insulator Temperature m a g n e t i s metal superconductor Electron concentration

Discoveries D-wave superconductivity PHASE DIAGRAM OF CUPRATES Pseudogap insulator Birgeneau Emery & Kivelson Stripes Temperature m a g n e t i s Three momentous discoveries in first decade: d-wave superconductivity – seminal contribution by Hardy and Bonn at UBC 2) Pseudogap – major contrinutions by Timusk at McMaster 3) Stripes – major contributions by Birgeneau, Emery, Kivelson metal superconductor Electron concentration

new forms of organization
High-Temperature Superconductivity Discoveries D-wave superconductivity PHASE DIAGRAM OF CUPRATES Pseudogap insulator Stripes Temperature m a g n e t i s Electrons in cuprates adopt entirely new forms of organization metal superconductor Electron concentration

Discoveries New ideas New states of matter Electron fractionalization Unification of magnetism and superconductivity Quantum criticality … After more than 100,000 publications, the problem has not yet been cracked. The mechanisms that govern the remarkable behaviour of electrons in these materials remain a mystery. The huge intellectual challenge is intact and it continues to capture the imagination of many of the best minds in the international scientific community. Many highly innovative theories have been proposed, including: New states of matter, e.g. with orbital currents – Laughlin, Kee, Lee, Chakravarty… Electron fractionalization, spin-charge separation – Anderson, Kivelson, Fisher, Senthil, … Unification of magnetism and superconductivity – Zhang

Discoveries New ideas New capabilities slit E qx Scanning tunneling spectroscopy Photoemission spectroscopy

Discoveries New ideas New capabilities New materials In the wake of this enormous worldwide effort, a qualitative change in the way condensed-matter and materials physicists do research has taken place, with the notion that oxides (and other materials) can be synthesized with an infinite number of structures and compositions, with novel properties. Two examples are the manganites and the ruthenates, where the first case of triplet superconductivity was discovered – a state analogous to the superfluidity of helium-3. Manganites – CMR Ruthenates – first p-wave superconductor Nickelates – static stripe order Spin ladders …

The problem has not been cracked !
High-Temperature Superconductivity Where do we stand in 2003 ? The problem has not been cracked !

Where do we stand in 2003 ? Much learnt, many open questions: Is antiferromagnetism responsible for superconductivity ? Are stripes good or bad for superconductivity ? Is spin-charge separation occuring ? Is 2D the key ? What is the nature of the pseudogap? Is there a hidden critical point? …

Our comparative advantage
Superconductivity Program Our comparative advantage MATERIALS SYNTHESIS COMPLEMENTARITY TRUE COLLABORATION

Interactions and collaboration
Two annual Program meetings – Spring & Fall Annual Summer School – organized by students Small scale meetings, joint experiments, etc Complementary expertise

Interactions and collaboration
Two annual Program meetings – Spring & Fall Annual Summer School – organized by students Small scale meetings, joint experiments, etc Complementary expertise Materials Theory Experiment

The power of collaboration
The definitive neutron experiments on cuprates Materials Theory Experiment D-density wave Neutron scattering YBCO crystals Laughlin, Kee Buyers, Birgeneau, Liang, Bonn, Taillefer Hardy

The power of collaboration
Elucidating the nature of superconductivity in ruthenates Materials Theory Experiment Sr2RuO Muons & Ultrasound Single crystals Rice, Sigrist, Luke, Taillefer Maeno Walker

The Future

Quantum Materials Some big questions:
How to achieve superconductivity at room temperature? What happens to electrons at a quantum critical point? Can quantum decoherence be mastered? Have we uncovered all distinct phases of matter?

A Program on Quantum Materials
Superconductivity Quantum magnetism Quantum phase transitions Organic conductors Research areas: Our general approach is to study materials in extreme situations where quantum phenomena manifest themselves in dramatic ways. Superconductors are the classic case of course - materials where at sufficiently low temperature the whole object behaves like one quantum-mechanical wave function. The analogous limit in nanoscience is to fabricate objects consisting of a small, countable number of atoms and electrons – an inherently quantum mechanical situation. In studying quantum critical points in condensed-matter physics, one takes a bulk material to an extreme situation and sees a state governed strongly by quantum mechanics, rather than being blurred by thermal effects. This removal of the “blurring” of quantum mechanics is also at the heart of quantum coherence and quantum computing. The best strategy for a CIAR program in this field is to have a wide range of complementary expertise (covering theory, experiment and materials synthesis) and activities in several of the key areas. To pick out one as the most promising would be risky and would deprive the network of the fruitful synergy that can come from interdisciplinarity. We propose a Program on Quantum Materials, a natural evolution of the Superconductivity Program. Rather than focus primarily on the unsolved problem of the cuprates, it would occupy a wide frontier in materials science – the physics of correlated electrons.

Superconductivity Research areas: The theoretical foundation for our understanding of electrons in matter breaks down. Cuprates The paradigm Two cornerstones of 20th century physics fail: Fermi-liquid theory of metallic state BCS theory of superconducting state In cuprate research, the underdoped regime remains the major focus. Studies of the vortex state (Birgeneau, Brewer, Buyers, Franz and Kallin) will shed light on the role of antiferromagnetism and tests of electron fractionalization will be pursued through studies of the anomalous normal state (Kim and Taillefer) and of individual vortices (Bonn and Moler). The oxygen-ordered crystals grown by Liang will allow us to make the definitive experiments, free of the uncertainties associated with imperfect samples.

“Research into superconductivity is enjoying a renaissance.”
A Program on Quantum Materials Superconductivity Research areas: New superconductors discovered since 2000 ferromagnetic superconductors MgB2 carbon nanotubes? carbon-60 iron (DNA??) As stated in the January 2002 issue of Physics World: “Research into superconductivity is enjoying a renaissance. Over the past two years physicists have discovered a wide variety of materials – including iron, single crystals of carbon-60 and DNA – that lose their electrical resistance at low temperatures”. For the first time, ferromagnetism and superconductivity – hitherto believed to be incompatible – were observed to coexist in a material. The discovery that magnesium diboride (MgB2) superconducts at 40 K sparked a worldwide race to uncover the basic properties of this humble black powder, and led to the largest special session at an American Physical Society meeting (in March 2001) since the “Woodstock” session on cuprates in 1987. The most dramatic findings come from the family of carbon structures called “fullerenes”. In 2001, a crystal of C60 molecules or “buckyballs” was made into a superconductor with a critical temperature in excess of 100 K, and thus comparable to that of cuprates. “Research into superconductivity is enjoying a renaissance.” Physics World, January 2002

Superconductivity Research areas: New superconductors ferromagnetic superconductors UGe2 Ferromagnetic superconductors offer a new arena in which to investigate the possibility of pairing via spin fluctuations. Luke, Taillefer and Walker have projects to elucidate the symmetry of the order parameter in these materials. Cambridge group (Lonzarich), 2000

Superconductivity Quantum magnetism Research areas: Most powerful probes of magnetism: Neutrons Muons TRIUMF NRC – Chalk River Both major facilities in Canada

Gradual breakdown of the Fermi liquid
A Program on Quantum Materials Superconductivity Quantum magnetism Quantum phase transitions Research areas: CeIn3 Gradual breakdown of the Fermi liquid New forms of organization In very general terms, the idea is to push electrons to their limits and watch them find new forms of organization. Explore with unprecedented control the breakdown of Fermi-liquid theory. In the cuprates, quantum phase transitions have become one of the current paradigms. As argued by Laughlin and others, much that is not understood about high-temperature superconductors has to do with a multiplicity of ordered phases. The big question is how the competition between these various ordered phases governs the overall properties. Confronting the problem of competing, ordered phases now involves us in a wide range of electron systems where we have greater control. Hence quantum phase transitions of several types will be studied: in magnetic metals (Dodge, Kim, Luke, Millis and Taillefer); in spin-Peierls systems (Bourbonnais); in overdoped cuprates (Taillefer and Timusk). Grenoble (Flouquet) & Cambridge (Lonzarich), 1998

Superconductivity Quantum magnetism Quantum phase transitions Organic conductors Research areas: - Mott insulator - Unconventional superconductivity - Interplay of magnetism and superconductivity - Luttinger liquid Research on organic and molecular conductors shares two key aspects of the science of cuprates. The first is the impact of reduced dimensionality – a very general (and incredibly rich) problem in condensed-matter physics. The second aspect is at the very heart of the cuprate problem: the effect of varying the electron concentration in taking the system from a Mott insulator to an unconventional superconductor to a metal. Activities in this area will include the work of Jérome and Bourbonnais on 1D and 2D organic superconductors. Orsay (Jérome) and Sherbrooke (Bourbonnais), 2001

From fits and flux integration
A Program on Quantum Materials Superconductivity Quantum magnetism Quantum phase transitions Organic conductors Nanostructures and mesoscopic physics Research areas: Tc~7K sample at T=2.1K From fits and flux integration ~1/4 0 <1 0 0.25 0 The study of electron behaviour in nanoscale structures is emerging as a major theme. We have projects in the theory of carbon nanotubes (Affleck, Bourbonnais and Kallin) and nanoscale superconductivity (Marsiglio), the nanofabrication of superconducting structures (Fournier and Wei), and the development of various probes such as scanning tunneling spectroscopy (Wei), scanning magnetic probes (Bonn and Moler) and beta-NMR at ISAC (Kiefl). Spin injection with STM Scanning magnetic probe Carbon nanotube

Superconductivity Quantum magnetism Quantum phase transitions Organic conductors Nanostructures and mesoscopic physics Solid-state quantum computing Research areas: If a real quantum computer is to see the light, it will rely on a solid-state device. The physics of “quantum decoherence” is the key fundamental issue. This is Philip Stamp’s main area of research, where he has recently been joined by theorists Gingras and Tremblay. D-wave systems is the only company in Canada developing solid-state qubits. It was created a few years ago by two young researchers coming out of the CIAR Superconductivity Program (Alex Zagoskin and Geordie Rose).

Quantum Materials Nanoelectronics Quantum Information Processing

Quantum Materials Superconductivity Nanostructures Quantum information
Applications UNDERSTANDING + CONTROL  example: superconducting QUBIT Superconductivity Nanostructures Quantum information Manipulating the Quantum State of an Electrical Circuit D. Vion, M. Devoret et al Science 3 May 2002

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