| Date & time | Speaker & affiliation | Talk title & abstract |
| Apr 5 4:00pm | Markus Deserno (Max Planck Institute, Mainz, Germany) | Fluid lipid membranes -- from physics to biology Abstract: Many interesting phenomena of bio-membranes occur in the range of several tens up to a few hundred nanometers -- budding, protein and lipid sorting, mediated interactions, rafts, etc. On such length scales many lipid-specific details have largely faded away, but pure continuum approaches may not yet be applicable. This is the realm of coarse-grained lipid models. Unfortunately it turns out that once the membrane really curves in space, the presence of bulk solvent becomes the dominant limiting factor in simulations. This is why people have been trying for a very long time now to eliminate the need for incorporating explicit solvent in simulations, but success has only been very recent. In this talk I will describe in some detail an efficient solvent-free simulation model developed in my group, discuss its physical properties, and illustrate its usefulness in a variety of applications, such as domain-induced budding, composition-curvature coupling, and membrane-mediated interactions. |
| Apr 12 4:00pm | Qimiao Si (Rice) | Quantum Critical Point beyond Order-Parameter Fluctuations
-- the Case of Heavy Fermion Metals |
| Apr 19 4:00pm | Kun Yang (National High Magnetic Field Lab and Florida State University) | Find Your Partner or Expel Your
Competitor: Exotic Pairing States in
Fermionic Superfluids with Unbalanced Pairing Species Abstract:Superfluidity in fermionic systems originates from pairing of fermions, and Bose condensation of these Cooper pairs. The Cooper pairs are usually made of fermions of different species; for example in superconductors they are pairs of electrons with opposite spins. Thus the most favorable situation for pairing and superfluidity is when the two species of fermions that form pairs have the same density, a situation successfully described by the Bardeen-Cooper-Schrieffer theory. It has become clear recently that pairing and superfluidity can also occur when the fermion species have different densities, in systems ranging from superconductors in a strong magnetic field to trapped cold atom systems, and quark matter in the core of neutron stars. Such a situation will necessarily lead to unpaired fermions in the ground state, and possibly non-trivial spatial structure in the superfluid order parameter. In this talk I will discuss the physics of such exotic pairing states, and their possible realization and detection in superconductors and cold atom systems. |
| Apr 26 4:00pm | Sumantha Tewari (Kavli Institute for Theoretical Physics, UCSB) | Living in dimension lower than meets the eye:
Sliding phases in classical and quantum
statistical mechanics Abstract: Sliding phases are phases that, in spite of living in a nominally higher dimension, possess surprising characteristics of a lower dimension. These phases have been discussed before in classical statistical mechanics in relation to Biology, and in quantum statistical mechanics in relation to the cuprate superconductors. Here, we consider quantum phase transitions in Josephson junction arrays and show that, in the presence of dissipation, the disordered phase in this extended system is a sliding phase in which the states of the local $(0+1)$-dimensional elements (single Josephson junctions) can slide past each other despite arbitrary range spatial couplings among them. The unusual character of the essentially local metal- superconductor quantum critical point can be tested by measuring the current voltage characteristics. This may be the simplest and most natural example of a sliding phase in nature. |
| May 3 4:00pm | Open | |
| May 10 4:00pm | Open | |
| May 17 4:00pm | Michael Lawler (University of Illinois at Urbana-Champaign) | The nematic instability of a Fermi fluid Abstract: I will discuss shape instabilities (Pomeranchuk) of the Fermi surface of a two dimensional Fermi fluid. I will focus on single particle properties of the nematic phase and quantum phase transition, measurable in STM and ARPES experiments. In particular, I will demonstrate the non-Fermi liquid physics that arises in the vicinity of this nematic instability. At finite temperatures (in the quantum critical regime), we also found the phenomena of 'local' quantum criticality: the fermion correlation length becomes ultra short near the phase transition. We believe these basic results may be applicable to Sr3Ru2O7, URu2Si2 and anisotropic quantum Hall phases while they may also be a general feature of many quantum critical points in itinerant fermion systems. |
| May 24 4:00pm | Antonio Castro Neto (Boston University) | The Amazing Properties of Two-Dimensional Carbon Abstract: Carbon is a life sustaining element that, due to the versatility of its bonding, is present in nature in many forms. Besides being an element which is fundamental for life on the planet, it has been explored recently for basic science and technology in the form of three-dimensional graphite, one-dimensional nanotubes, zero-dimensional fullerenes, and more recently in the form of two-dimensional Carbon, also known as graphene. I am going to talk about the theoretical description of graphene in the light of new experiments in this material. Contrary to ordinary metals and semiconductors, graphene has unusual electronic properties that cannot be described by standard theories, such as Landau's Fermi liquid theory. Understanding of the electronic properties of graphene may open doors for new carbon-based nano-electronics. |
| May 31 4:00pm | Open | |
| June 7 4:00pm | Benedikt Binz (UC, Berkeley) | Magnetic domain formation in itinerant metamagnets Abstract: I will discuss the effects of long-range dipolar forces on metamagnetic transitions, i.e. phase transitions which are triggered by magnetic field. By generalizing the theory of Condon domains to the case of a system undergoing a first-order metamagnetic transition, it will be demonstrated that dipolar interactions induce a spatial modulation of the magnetization in the form of stripes or bubbles within a finite range of the applied field. The general theory is applied to the bilayer ruthenate Sr3Ru2O7, where some kind of inhomogeneous phase is believed to occur close to a quantum critical endpoint. |
Seminars for Fall 2005
Seminars for Winter 2006