Scope
SCES'07 will cover a wide range of topics in the diverse area of strongly correlated systems. The correlated electronic and magnetic materials to be featured include f-electron based heavy fermion intermetallics, d-electron based transition metal compounds, and organic solids. Nanoscale structures and ultracold atoms in optical lattices, which have emerged as model systems to study correlation physics, will also be addressed. The conference will seek to deepen our understanding of the rich physical phenomena that arise from correlation effects. The anticipated focus will be on quantum phase transitions, non-Fermi liquid phenomena, quantum magnetism, unconventional superconductivity, and metal-insulator transitions. Both experimental and theoretical work will be highlighted. Mathematical models and computational studies will also be covered.
The conference will provide a forum to present new research and exchange new ideas. It will also facilitate cross fertilization among the different subjects, and introduce these subjects to junior researchers. Presentations will consist of plenary, invited and contributed talks/symposia complemented by busy poster sessions.
SCES’07 will add Houston to the long list of cities that welcomed the conference series: Sendai (’92), San Diego (’93), Amsterdam (’94), Goa (’95), Zürich (’96), Paris (’98), Nagano (’99), Ann Arbor (’01), Krakow (’02), Karlsruhe (’04), and Vienna (’05). Every three years since 1997, SCES has been joining the triennial International Conference on Magnetism, held in: Cairns (’97), Recife (’00), Rome (’03), and Kyoto (’06).
List of Topics
- Quantum phase transitions
- Heavy fermion systems
- Quantum magnetism and frustrated magnets
- High temperature superconductivity
- Organic conductors and magnets
- Low dimensional systems
- Non-Fermi liquids and exotic quantum phases
- Unconventional and novel superconductors
- Kondo impurity and Kondo lattice systems
- Mott-Hubbard systems
- Interplay between spin-, charge- and orbital degrees of freedom
- Correlated electrons in nanostructures
- Quantum Hall liquids
- Mathematical models and computational studies
- Correlated atoms in optical lattices
- New developments
Highlights
Each week we feature some general-audience highlight on the main page of the conference website in order to convey the flavor and excitement of the topics that will be discussed during the meeting. You can find here the list of our past highlights:
Week of Feb 19th
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Modern Alchemy
Source:
P. Canfield (Ames)
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One of the historic goals of alchemy was to turn base elements into precious ones. Although the practice of alchemy has been superseded by chemistry and solid state physics, the desire to dramatically change or tune the properties of a compound, preferably through small changes in composition remains, especially for compounds that can be tuned to extremes in behavior. Here we report a new family of compounds which is over 85% Zn and yet can be tuned to have properties ranging from those of copper to those of a ferromagnet or a correlated material with extraordinarily heavy electrons. Whereas this is not quite turning lead into gold, it is essentially tuning Zn to become a variety of model compounds.
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Week of February 26th
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Quantum Fluctuations
Source:
P. Gegenwart (Goettingen)
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Microscopic particles in matter can never be entirely stationary, even at absolute zero temperature. This dictation of quantum mechanics gives rise to quantum critical points, where bulk matter undergoes smooth transformations from one quantum phase to another. Their proper theoretical description is challenging because the fluctuations are both collective and quantum mechanical. Traditionally, quantum criticality is described by the spatial and temporal fluctuations of a classical variable -- Landau's order parameter. We provide experimental evidence that quantum criticality can contain low energy scales that go beyond the one associated with the slow fluctuations of the order parameter, implying that, in contrast to conventional wisdom, the theory of quantum criticality needs to incorporate inherently quantum degrees of freedom.
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Week of March 5th
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Puzzling Excitations Probed by X-rays
Source:
D. Ellis (Toronto)
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There has yet to be a coherent picture of how high temperature superconductivity works. If the problem is seen as a big jigsaw puzzle, then the pieces would consist of the many experiments, all of which must fit together. One important way of learning about a system is to probe its excitations. What does it take to excite a system, how do these excitations form and what are their properties? In this research x-rays are used to impart energy and momentum to single crystals related to the superconductors, exciting their electrons to higher energy states. These excited states are studied in terms of their energy vs. momentum relations, as well as dependence on temperature and crystal impurity. |
Week of March 12th
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De-Haas-van-Alphen Meets SCES
Source:
C. Capan (Baton Rouge)
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An electron placed in a magnetic field orbits in a plane perpendicular to the field direction. This so called cyclotron motion is responsible for additional resistance to the flow of electrical current in the metal. In the presence of strong magnetic fields, this also leads to oscillations in the magnetic properties of the metal. These oscillations are periodic in the inverse of the magnitude of the applied magnetic field. This oscillatory effect allows the experimental mapping of the topology of the motion, both magnitude and direction of the electrons contributing to current flow, characteristic of each metal. We have observed an anomalous damping of these oscillations accompanying a field induced magnetic transformation, which is a signature of strong interactions among the conduction electrons. |
Week of March 19th
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Turning Metals into Insulators
Source:
M.C.O. Aguiar (Belo Horizonte)
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In systems for which the electron-electron interaction (U) is larger than the electronic kinetic energy, a transition from a metallic phase to an insulator phase is observed as U increases. This is known as the Mott-Hubbard transition. In systems for which U=0, but disorder is present, a metal-insulator transition can happen as disorder increases. It corresponds to the so-called Anderson localization transition. If both electron-electron interaction and disorder are present, there is an interplay of interaction and Anderson localization effects, which can drive the system through a Mott-Anderson transition. In this work, we present the phase diagram for interacting and disordered systems and discuss scaling properties that are valid close to the Mott-Anderson transition. |
Week of March 26th
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Electrons Feel the Inhomogeneous Vibe
Source:
J. Lorenzana (Rome)
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After 20 years of the discovery the mechanism of high temperature superconductivity (HTSC) is still a mystery. In the last years it has became clear that HTSC tend to become electronically inhomogeneous at a scale of a few atomic constants. A key question is if this inhomogeneity is detrimental to superconductivity or if it helps it. Old superconductors work thanks to the help of atomic vibrations. Just as a lattice of atoms have vibrational modes that you do not find in the homogeneous liquid phase an inhomogeneous electronic state can support new electronic vibrational modes that are not present in an homogeneous electronic fluid. In this talk we will present computations of this new electronic vibrational modes which may underline the mechanism of HTSC. |
Week of April 2nd
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Electrons Get Excited About Spin-Waves
Source:
S. Yamamoto (Houston)
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Two different species of electrons are important in heavy fermion compounds. One species is free to move around and is involved in the collective phenomenon of electrical conduction. The other species is bound to a well-ordered lattice, but participates in collective magnetic processes. When the two types of electrons interact with each other, a competition ensues between the various types of collective behavior that may exist in the composite system. We study this system, called a Kondo lattice, by using a popular model known as the nonlinear sigma model. This leads to exact results -- which are usually hard to achieve theoretically in more than one spatial dimension -- on the Kondo lattice. |
Week of April 9th
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Electrons in Square Dance
Source:
C. Zhou (Oak Ridge)
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Under extremely low temperatures, electrons of very low density and confined in two dimensions crystalize. However, quantum mechanics predicts that multiple electrons in this crystal would prefer to dance in a highly choreographed pattern that results in different magnetic phases of the system. We found that the mass anisotropy, which is a property that electrons usually do not enjoy in the free space, but common to those confined in semiconductors, selects a theme for their collective performance. |
Week of April 16th
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Squeezing Superconductivity Out
Source:
J. Schilling (St. Louis)
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In the periodic table only 29 elements are superconducting. However, if high pressures are applied, 23 further elements become superconducting (for example, oxygen, boron, silicon, and iron). High pressures may also increase significantly the value of the superconducting transition temperature, for Y to 20 K and for Ca to even 25 K. Higher values may be possible at higher pressures. These experiments are designed to explore how high the transition temperature may go in an elemental superconductor and thus contribute to the overarching goal to eventually raise this temperature to values near room temperature. This would lead to a widespread use of superconductors in our society. |
Week of April 23rd
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Slow Electrons in Exotic States
Source:
S. Julian (Toronto)
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In the past 20 years a class of metals has been discovered in which charge-carrying electrons move much more slowly than in normal metals (such as the copper wires used to carry current to people's homes). This slowness is a result of interactions between the electrons, and it allows them to form some exotic states, such as strange superconducting states. This talk addresses an extremely powerful measurement technique, called the de Haas van Alphen effect, that can be applied to learn about how the electrons move in these materials. |
Week of April 30th
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Squeezing the Jam Out of Electrons
Source:
A. Holmes (Osaka)
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Many of the most interesting phenomena in everyday life are so-called emergent behaviors: From traffic jams to termite mounds, complex systems can act in a way vastly different to the sum of their parts. As always, we try to find a simple model containing the essence of a system that we can manipulate in a controllable way. These phenomena are often found between competing states: When the density of traffic on a highway increases to just below gridlock, the actions of a single car can have huge knock-on effects. Our traffic is made of electrons in a crystalline lattice; we apply pressure by squeezing between diamonds, and causing all sorts of interesting collective behavior in the process. |
Week of May 7th
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New Phenomena Emerging Near Quantum Criticality
Source:
S. Wada (Kobe)
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The study of a continuous transition between localised and delocalised electrons in solids is at the forefront of condensed matter physics. This is because of the interest not only in the basic mechanism of the transition but also in many exotic physical phenomena that emerge in the vicinity of the transition, such as a breakdown of the Landau Fermi liquid theory, unconventional superconductivity, and multipolar ordering. In addition, it is very likely that a further new phase hides behind the transition. Here we present an alternative insight into the important role of intermediate valences on the non Fermi liquid phenomena based on the experimental measurements for ytterbium-based materials in the vicinity of the quantum critical point close to zero-temperature |
Week of May 14th
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Exotic Behavior of the Magnetic Lattice in Superconductors
Source:
C. Bowell (Birmingham)
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In certain types of superconductor, placed in a magnetic field, the field only penetrates the superconductor in "tubes". These tubes have a diameter 1000 times smaller than the width of a human hair. They form a magnetic lattice throughout the superconductor and, like any lattice, temperature can cause it to melt into a liquid. Melting has been found to occur in "High-Tc" superconductors, where temperatures reach only -150 degrees Celsius. It is also expected to occur in superconductors which stop being superconducting at much lower temperatures, like the element niobium. By studying the magnetic lattice of niobium using neutron scattering, we have found that the magnetic lattice does not melt, so the interesting question to ask now is... why not? |
These highlights were sponsored by:
 
See Sponsors for a full list of conference sponsorships
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