Cornell professors Harry Greene, Paul Sawyer, Robert Smith and Robert Thorne have been chosen for the 2011 Stephen H. Weiss Presidential Fellowships, the Cornell Board of Trustees announced at the Jan. 21-22 meeting in New York City. more
Author Archives: je277
The physics of turbulent flow is everywhere
From the mixing of milk in coffee to the formation of raindrops in clouds, the physics of turbulent flow is everywhere. Researchers at Cornell have discovered that seemingly random turbulent flows, which are the flow of a fluid in which velocity varies rapidly and irregularly, actually have an astonishing structure.
The work, published online June 5 in the journal Nature Physics, was led by Eberhard Bodenschatz, Cornell adjunct professor of physics and of mechanical and aerospace engineering. The work was in collaboration with researchers Haitao Xu of the Max Planck Institute for Dynamics and Self-Organization in Germany and Alain Pumir of Ecole Normale Supérieure de Lyon in France. more
Paul McEuen elected to National Academy of Sciences
Cornell professors Jon Kleinberg and Paul McEuen, and Weill Cornell professor Carl Nathan are among 72 new members of the National Academy of Sciences.
McEuen, the Goldwin Smith Professor of Physics and director of the Kavli Institute at Cornell for Nanoscale Science and the Laboratory of Atomic and Solid State Physics (LASSP), studies the electrical and mechanical properties of carbon nanomaterials.
McEuen’s group has conducted seminal studies of carbon nanotubes, quantum dots and single molecules. Recently he discovered that single photons can create multiple electron-hole pairs in carbon-nanotube photodiodes, suggesting a new strategy for enhancing efficiency in photovoltaic devices. more
David Mermin is awarded Majorana Prize
N. David Mermin received this prize for his fundamental contributions on the solid state physics, quantum field theory and statistical mechanics, especially Mermin-Wagner theorem and its remarkable applications. And for his promoting the scientific international interdisciplinary collaborations. To read more about Majorana Prize awardees seehttp://www.majoranaprize.com/
Sol Gruner elected to AAAS
University faculty elected to membership in the American Academy of Arts and Sciences. more
The Theory of the Nodal Nematic Quantum Chirality
Eun-Ah Kim, Stanford University
2/7/08 – 4:30 p.m., 700 Clark Hall
In the last several years, experimental evidence has accumulated in a variety of highly correlated electronic systems of new quantum phases which (for purely electronic reasons) spontaneously break the rotational (point group) symmetry of the underlying crystal. Such “nematic” phases have been seen in quantum Hall systems, in the metamagnetic SrRuO, and more recently in magnetic neutron scattering studies of the high temperature superconductor, YBCO.
The quantum dynamics of the nematic order parameter, especially near a putative quantum critical point, naturally couples strongly to low energy fermionic excitations (quasiparticles). Such coupling can affect the nature and even the fate of quasiparticles making a study of nematic quantum criticality a highly nontrivial problem. In this talk, I will discuss our recent results on one case in which this problem can be attacked in a tractable manner: the nodal nematic quantum criticality. Deep inside a d-wave superconducting state in a two-dimensional tetragonal crystal, the phase space for the low energy fermions reduce from the entire Fermi surface to four nodal points. The limited phase space for scattering allows for a controlled analysis of the nematic quantum criticality for nodal fermions.
We study the character of this quantum phase transition. We investigated the problem by solving a model system with $N$ flavors of quasiparticles in the large N limit. We find the transition to be continuous in this limit and the critical nematic fluctuations to have drastic effects on the nature of nodal quasiparticles. To leading order in 1/N, quantum fluctuations enhance the dispersion anisotropy of the nodal excitations, and cause strongly angle dependent scattering leading to a nontrivial structure in the single particle spectral function. I will discuss possible implications of our results for cuprate physics from the spectral function of the nematic mode and the single fermion spectral function.
3D Topological Insulators and 2D Anderson Delocalization
Speaker: Shinsei Ryu, University of California, Santa Barbara
2/5/08
4:30 p.m., 700 Clark Hall
Recently, a new type of insulators, called Z2 topological insulator, has been discovered. They can be thought of as a close cousin of the integer quantum Hall insulators, but different from the IQHE in many essential ways: Z2 topological insulators exist in systems that respect time reversal symmetry, can be either in 2D or 3D, and are characterized by a Z2 topological number, unlike the integral Hall conductance in the IQHE. Several candidate materials possessing the non-trivial Z2 topological features, such as HgTe quantum wells, and Bismuth-Antimony alloys, have been proposed and tested experimentally. In this talk, we will discuss quantum transport of 2D surface massless Dirac fermion states supported by 3D Z2 topological insulators terminated by a 2D boundary. Although these Dirac fermion states, from the symmetry point of view, belong to the 2D spin-orbit (symplectic) symmetry class of Anderson localization, they inherit the Z2 topological character of the bulk, and exhibit different response to impurities from conventional disorderedconductors with spin-orbit interactions. We also briefly discuss that this surface physics of 3D Z2 topological insulators can be simulated by graphene.