Experimental Research Programs
Tulane Group Members: Olga Dulub, Yunbin He, Peter Jacobson, Bulat Katsiev, Erie Morales, Rachel Oerter
During the last thirty years, tremendous success has been made in the development of theoretical and experimental techniques for investigation of solid surfaces. The geometric, electronic and vibrational structure as well as the chemistry and reactivity of solid surfaces can now be investigated with unprecedented detail. Fundamental knowledge from these investigations has big impact in such diverse fields as semiconductor industry and catalysis. Our research focus is the investigation and modification of surfaces of materials which have not been extensively investigated with surface science techniques; especially metal compounds such as oxides, nitrides, and silicides.
Current projects of our surface science group include the surface geometric structure of single-crystalline oxides, adsorption of molecules, and ultrathin film growth. State-of-the art ultrahigh vacuum equipment is used for the experimental part of the research. In-situ Scanning Tunneling Microscopy and low-energy electron diffraction is used for studying surface morphologies and atomic structure. Spectroscopic techniques such as laboratory-based x-ray photoelectron spectroscopy and high-resolution photoemission studies at synchrotron radiation sources complement the research program.
Tulane Group Members: Yinwan Li, Timothy Schuler
Professor David L. Ederer was a senior staff scientist in the Center for Atomic, Molecular and Optical Physics at the National Institute of Standards and Technology (NIST), for almost thirty years. He came to Tulane in January 1992 to launch a new program in experimental solid state physics with the Center for Advanced Microstructures and Devices (CAMD) in Baton Rouge, as a focal point. Ederer carries out research on transition metals and rare earth materials at the Advanced Light Source as well, using soft x-rays to elucidate the electronic properties of complex and highly correlated materials such as high Tc superconductors. Ederer, a fellow of the American Physical Society, is an internationally recognized expert in the use of synchrotron radiation for research in atomic, molecular, and solid state physics. His research in atomic, and condensed matter physics, as well as instrument design has resulted in over one hundred and fifty papers.
Recent topics of research have included doped manganate systems, the superconducting perovskite Sr2RuO4 system and multi-layered variants, and magnetically doped semiconductors with particular focus on half-metallic behaviour.
Tulane Group Members: Zhe Qu, David Fobes, Tijiang Liu, Jin Peng
The research interest of my group primarily focuses on spin triplet superconductivity in Sr2RuO4 and novel quantum phenomena in other interesting ruthenates such as Sr3Ru2O7, BaRu6O12 and La4Ru6O19. Sr2RuO4 possesses a similar crystal structure to the high-Tc superconductors, but it displays unique properties fundamentally different from those of high-Tc and conventional superconductors. A spin-triplet pairing occurs in the superconducting state, in sharp contrast with the spin-singlet pairing of other known superconductors. However, there is still controversy over the symmetry of the orbital part of the pair wave function for this new superconductor. We are carrying out directional single-particle tunneling measurements to determine the orbital pairing symmetry and the orbital dependence of superconductivity. Sr3Ru2O7, BaRu6O12 and La4Ru6O19 are not superconductors, but they show very interesting physical properties at low temperature. Sr3Ru2O7 exhibits a metamagnetic quantum phase transition. BaRu6O12 shows quasi-one-dimensional characteristics electronically and is also likely in the vicinity of a quantum phase transition. La4Ru6O19 shows non-Fermi-liquid behavior.
We are attempting to find the ideal conditions for growing extremely high purity single crystals of these materials with a floating-zone furnace, aiming to search for novel quantum phenomena at extremely low temperatures.
Principle Investigator: Wayne Reed
Tulane Group Members: Alina Alb, Mike Drenski, Pascal Enohnyaket, Tomasz Kreft
Research in my group centers on fundamental and applied aspects of Polymer Science, with an increasing emphasis on private sector liaison. We study biological and synthetic polymers in solution, with an aim towards discovering basic physical principals involved in their structures and interactions, as well as solving practical problems of immediate interest to such industries as pharmaceuticals, biotechnology, food, paints, adhesives, resins, coating, water purification, etc. To this end we are also strongly involved in developing new characterization techniques and instrumentation for polymers, especially those involving light scattering.
Efforts are concentrated on innovative ways of monitoring processes occurring in polymer solutions in real time. We make extensive use of light scattering and other optical techniques, viscometry, size exclusion chromatography, and other auxiliary techniques (DSC, electron-microscopy, etc.). We have interests in the fundamental areas of polymer reaction kinetics and mechanisms, conformations, interactions and hydrodynamics, with a special focus on polyelectrolytes.
Tulane Group Members: Alexander Laptev, Michael Huber, Carroll Trull, Ilan Stern
My group is engaged in experimental nuclear physics research using cold and ultracold neutrons. This work falls into three related, but distinct categories:
(1) tests of the Electroweak Standard Model with precision measurements of neutron decay parameters;
(2) studies of the hadronic weak interaction by measuring parity-violating parameters in neutron interactions with matter;
(3) tests of nucleon forces and fundamental quantum mechanics using neutron interferometery. Our main focus right now is on categories (1) and (3).
Cold neutrons are free neutrons that are moving so slowly (less than 2000 m/s) that their deBroglie wavelengths are larger than the spacing between atoms in matter, typically in the range 0.2 to 2.0 nm. In this regime the neutron-matter interaction is coherent, the neutron interacts with many atoms simultaneously, and so it is more wave-like than particle-like. Cold neutrons can be manipulated optically, in many ways similar to light optics. They can be reflected, refracted, and diffracted in matter. Neutron guides, analogous to fiber optic guides, can be used to transport cold neutrons long distances with very little losses.
Ultracold neutrons (UCN's) are neutrons whose kinetic energy is less than about 300 neV. This energy is comparable to three important energy scales:
(1) the neutron's optical potential in certain materials;
(2) the neutron's potential energy in a strong magnetic field (~ 5 Tesla);
(3) the neutron's gravitational potential energy at a height of several meters. Therefore UCN's can be trapped optically, magnetically, and gravitationally.
A free neutron will decay into a proton, electron, and antineutrino with a lifetime of about 15 minues. This is the simplest nuclear beta decay and the prototype semi-leptonic weak decay. The measurable parameters of neutron decay such as its lifetime and angular correlations can be directly related to fundamental parameters in the Electroweak Standard Model. Precision experiments can test the self-consistency of the theory and possibly point to new physics related to grand unification. In this way neutron decay plays an important role in the low-energy frontier of particle physics.
Precise measurements of neutron scattering lengths using a neutron interferometer can be used to improve our understanding of the nucleon-nucleon potential and other parameters such as the charge radius of the neutron. The neutron interferometer is also used for fundamental tests of quantum mechanics.
These experiments are carried out at the National Institute of Standards and Technology (NIST) [Center for Neutron Research]
In addition to comprehensive instrumentation for neutron scattering research, this facility supports and operates a suite of neutron beams (both monochromatic and polychromatic) dedicated to fundamental neutron physics (link).
It also operates the most sensitive neutron interferometer (link) in the world.
We design and develop experiments in our laboratories at Tulane, usually in collaboration with groups at other institutions, and then bring experiments to NIST for data collection. We usually spend summers at NIST and students in my group often spend one or more years full time at NIST, after completing their Tulane course-work, to complete their dissertation research.
Upcoming experiments:
-A measurement of the radiative decay branch of the neutron (never before observed).
-A precision measurement of the electron-antineutrino correlation (little "a") in neutron decay.
-A precision measurement of the neutron-electron scattering length. This will lead to a determination of the charge radius of the neutron.
-An improved measurement of the neutron scattering length in polarized 3He gas. This will provide important and unique information about nucleon-nucleon forces.
-A new measurement of gravitationally-induced quantum interference in a neutron interferometer. This tests the weak equivalence principle at the quantum limit.
