Bulletin of the American Physical Society
2011 Annual Meeting of the Four Corners Section of the APS
Volume 56, Number 11
Friday–Saturday, October 21–22, 2011; Tuscon, Arizona
Session L1: Plenary Session III |
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Chair: James Chisholm, South Utah University Room: UA Student Union South Ballroom |
Saturday, October 22, 2011 9:55AM - 10:31AM |
L1.00001: Nanomagnetism Invited Speaker: Nanomagnets have excellent potential for enhancing existing technologies such as magnetic storage media and magnetic sensors and they may also find new applications in biomedicine and spintronics, devices that exploit not only the charge of the electron but also its spin. In general, the magnetic properties of ferromagnets can be understood in terms of competition among the magneto-crystalline, exchange, and magnetostatic energies due to long range dipole-dipole interactions. Confinement in nanomagnets alters their energetics and leads to new magnetic states and interfaces also become increasingly important on these length scales. We have used a variety of time- and frequency domain experimental techniques, combined with numerical micromagnetic simulations to explore and understand the magnetization dynamics in nanomaterials. I will discuss some of the interesting research topics in the field, including the dynamic properties of magnetic vortices that are often found in the ground state of magnetically soft patterned structures. [Preview Abstract] |
Saturday, October 22, 2011 10:31AM - 11:07AM |
L1.00002: Quantum metrology -- optical atomic clocks and many-body physics. Invited Speaker: Optical clocks based on atoms confined in optical lattices provide a unique opportunity for precise study and measurement of quantum many- body systems. The state-of-the-art optical lattice clock has reached an overall fractional frequency uncertainty of 1 $\times $ 10$^{-16}$ [1]. One dominant contribution to this uncertainty is clock frequency shift arising from atomic collisions. Collisions between initially identical fermionic Sr atoms can occur when they are subject to slightly inhomogeneous optical excitations during the clock operation [2]. We have recently implemented a seemingly paradoxical solution to the collisionshift problem: with a strong atomic confinement in one-dimensional tube-shaped optical traps, we dramatically increase the atomic interactions. Instead of a naively expected increase of collisional frequency shifts, these shifts are increasingly suppressed [3]. The large atomic interaction strength creates an effective energy gap in the system such that inhomogeneous excitations can no longer drive fermions into a pseudo-spin antisymmetric state, and hence their collisions and the corresponding frequency shifts are suppressed. We demonstrate the effectiveness of this approach by reducing the density-related frequency shift to the level of 10$^{-17}$, representing more than a factor of ten reduction from the previous record [1, 2]. In addition, we have observed well-resolved interaction sidebands separated from the main peak of the clock transition, giving a direct evidence for the removal of the interaction energy from the clock carrier transition. Control of atomic interactions at the level of 1 $\times $ 10$^{-17 }$is a testimony to our understanding of a quantum many-body system and it removes an important obstacle for building an optical atomic clock based on such systems with high accuracy. \\[4pt] [1] A. D. Ludlow \textit{et al., }Science \textbf{319}, 1805 (2008). \\[0pt] [2] G. K. Campbell \textit{et al., }Science \textbf{324}, 360 (2009). \\[0pt] [3] M. D. Swallows \textit{et al}., Science \textbf{331}, 1043 (2011). [Preview Abstract] |
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