Bulletin of the American Physical Society
2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007; Denver, Colorado
Session V38: Focus Session: Instrumentation and Metrology for Fundamental Physics 
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Sponsoring Units: GIMS Chair: J. Geremia, University of New Mexico Room: Colorado Convention Center 501 
Thursday, March 8, 2007 11:15AM  11:51AM 
V38.00001: Mechanical effects of strong measurement: backaction noise and cooling Invited Speaker: Keith Schwab Our recent experiments show that it is now possible to prepare and measure mechanical systems with thermal occupation factors of N$\sim $25 and perform continuous position measurements close to the limits required by the Heisenberg Uncertainty Principle (1). I will discuss our backaction measurements with nanomechanical structures strongly coupled to single electron transistors. We have been able to observe the stochastic backaction forces exerted by the SET as well as a cooling effect which has analogies to cooling in optical cavities. Furthermore, I will discuss progress using optical fields coupled to mechanical modes which show substantial cooling using the pondermotive effects of the photons impacting a flexible dielectric mirror (2). Both of these techniques pave the way to demonstrating the true quantum properties of a mechanical device: squeezed states, superposition states, and entangled states. \newline \newline (1) ``Quantum Measurement Backaction and Cooling Observed with a Nanomechanical Resonator,'' A. Naik, O. Buu, M.D. LaHaye, M.P. Blencowe, A.D. Armour, A.A. Clerk, K.C. Schwab, \textit{Nature}\textbf{ 443}, 193 (2006). \newline (2) ``Selfcooling of a micromirror by radiation pressure,'' S. Gigan, H.R. Boehm, M. Patemostro, F. Blaser, G. Langer, J. Hertzberg, K. Schwab, D. Baeuerle, M. Aspelmeyer, A. Zeilinger, \textit{Nature} \textbf{444}, 67 (2006). [Preview Abstract] 
Thursday, March 8, 2007 11:51AM  12:03PM 
V38.00002: An apparatus for measuring shortrange deviations from Newtonian gravity including a magnetic force calibration Andrew Geraci, David Weld, John Chiaverini, Sylvia Smullin, Aharon Kapitulnik Several recent theories suggest that new physics related to gravity may appear at short length scales. For example, light moduli or particles in ``large'' extra dimensions could mediate macroscopic forces of(super)gravitational strength at length scales below a millimeter. We have built an apparatus utilizing cryogenic microcantilevers capable of measuring attoNewton forces [1], which now includes a magnetic analog for force calibration. Our most recent experimental constraints on Yukawatype deviations from Newtonian gravity will be presented. \newline References: \newline [1] J. Chiaverini, S. J. Smullin, A. A. Geraci, D. M. Weld, A. Kapitulnik, Phys.Rev.Lett. {\bf{90}}, 151101 (2003). S. J. Smullin, A.A.Geraci, D.M.Weld, J.Chiaverini, S.Holmes, and A. Kapitulnik, Phys. Rev. D 72, 122001 (2005). [Preview Abstract] 

V38.00003: ABSTRACT WITHDRAWN 
Thursday, March 8, 2007 12:15PM  12:27PM 
V38.00004: Feedback Control and Characterization of a Microcantilever Using Optical Radiation Pressure David Weld, Aharon Kapitulnik We describe a simple method for feedbackregulation of the response of a microcantilever using the radiation pressure of a laser. A modified fiberoptic interferometer uses one laser to read out the position of the cantilever and another laser of a different wavelength to apply a force that is a phaseshifted function of that position. The method does not require a highfinesse cavity, and the feedback force is due solely to the momentum of the photons in the second laser. The feedback phase can be adjusted to increase or decrease the microcantilever's effective quality factor $Q_{\mathrm{eff}}$ and effective temperature $T_{\mathrm{eff}}$. We demonstrate a reduction of both $Q_{\mathrm{eff}}$ and $T_{\mathrm{eff}}$ of a silicon nitride microcantilever by more than a factor of 15 using a rootmeansquare optical power variation of $\sim$2~$\mu$W. This technique was developed to control the response of a cantilever used as a force sensor in a nextgeneration test of Newtonian gravity at length scales of 20~$\mu$m. Additionally, we suggest a method for determination of the spring constant of a cantilever using the known force exerted on it by radiation pressure. [Preview Abstract] 
Thursday, March 8, 2007 12:27PM  12:39PM 
V38.00005: SQUIDbased magnetic thermometry for fundamental physics and applications below $1$ K R. Sultan, R. Rahman, F. Baset, B. L. Zink One approach to sensitive thermometry below $1$ K is to measure the temperaturedependent magnetization of a paramagnet using a SQUID. Devices based on bulk materials (such as cerium manganese nitrate) and superconducting transformers provide some of the most sensitive thermometers available for dilutionrefrigerator temperatures. Microcalorimeter xray or $\gamma$ray detectors can be made using the same concept, with a small erbiumdoped gold paramagnet (again prepared using bulk techniques) measured with a thinfilm dc SQUID magnetometer. In this talk we describe our recent work toward a SQUIDbased magnetic thermometer fabricated entirely using thinfilm techniques. This thermometer has potential applications not only for high spectralresolution xray detectors, but also for fundamental measurements of thermal transport in thinfilms and nanostructures. We will discuss optimization of a lownoise dc SQUID and its coupling to the sensor, the choice of a paramagnetic thinfilm, and the performance of the thermometer for various applications. [Preview Abstract] 
Thursday, March 8, 2007 12:39PM  12:51PM 
V38.00006: Shot Noise Thermometry down to 10 mK Lafe Spietz, Robert Schoelkopf We report measurements of the Shot Noise Thermometer (SNT), a primary thermometer based on the electronic noise from a tunnel junction, in the range from 10 mK to 200 mK. We demonstrate operation of the SNT down to 10 mK with 10\% accuracy at the lowest measured temperature. At 10 mK, where for a measurement frequency of f=450 MHz, $hf=2.5k_BT$, we demonstrate that, provided that quantum corrections are taken into account, the SNT continues to be a practical thermometer. We also show that selfheating is not a measurable problem and demonstrate a simplified readout of the SNT. [Preview Abstract] 
Thursday, March 8, 2007 12:51PM  1:03PM 
V38.00007: A new approach to the measurement of relaxation heat capacity. Jonathan B. Betts, Albert Migliori, Izabela Stroe, Scott Riggs We have developed lowaddenda calorimeters for the 300mK  380K temperature range. The low addenda produces a calorimeter relaxation response with exceptionally low scatter, typically less than one part in 1000. Such low scatter exposes small errors in the usual logarithmic variation of temperature with time, and because of the low scatter, small corrections to this function can be made consistently, increasing our heatcapacity precision by an order of magnitude. We also present a calorimeter design for measuring small microliter liquid samples using the relaxation method in the 300K  400K temperature range. [Preview Abstract] 
Thursday, March 8, 2007 1:03PM  1:15PM 
V38.00008: A new thin film nanocalorimeter for measuring the heat capacity of 50nm films from 300mK to 500K. Daniel Queen, Frances Hellman Low stress silicon nitride is used in a variety of MEMS devices as an important mechanical membrane material. The high Debye temperature of the silicon nitride makes it an ideal material for use in a MEMS based calorimeter. Microfabrication techniques provide for a high degree of reproducibility between devices on a single silicon wafer. Microcalorimeters based on low stress silicon nitride have been successfully used to measure the heat capacity of 200nm films and small single crystals ($\sim $50 micrograms) for over a decade. We report results on a scaled down calorimeter for measurements of 50nm thin films. By scaling down the dimensions of the device, we have reduced the background addenda by an order of magnitude as compared to previous designs. The resulting decrease in die size allows us to use the nanocalorimeter in confined spaces such as small bore magnets and beam lines. [Preview Abstract] 
Thursday, March 8, 2007 1:15PM  1:27PM 
V38.00009: New design of a microcalorimeter with enhanced accuracy through the consideration of thermal loss of the membrane platform K. S. Suh, H. J. Kim, J. W. Kim, Y. D. Park, Kee Hoon Kim We report on the development of a SiN/Si based microcalorimeter for measuring specific heat of small samples in a wide temperature range. By using wellknown MEMS fabrication techniques [1], the heater and sensor elements are integrated on the SiN membrane. The fabricated calorimeter is operated by a custommade program based on the curve fitting method [2]. By comparing measured thermal conductance ($\lambda )$ from the membrane platform to the thermal reservoir in three different designs, we find $\lambda $ can critically affect the accuracy of measurement, and that the geometry of metal lines is a key parameter to control$\lambda $. Based on those findings, we provide a new design of microcalorimeter resulting in the specific heat of Cu ($\sim $ 300 $\mu g)$ consistent with literature values within 5{\%} in a temperature range between 20 and 300 K. \newline {\dag}parkyd@phya.snu.ac.kr, khkim@phya.snu.ac.kr \newline [1] D. W. Denlinger \textit{et al.}, Rev. Sci. Instrum. 65, 946 (1994); S. L. Lai \textit{et al.}, Appl. Phys. Lett. 67, 1229 (1995). \newline [2] K. S. Suh \textit{et al.}, J. Korean Phys. Soc. 49, 1370 (2006); J. S. Hwang \textit{et al.}, Rev. Sci. Instrum. 68, 94 (1997). [Preview Abstract] 
Thursday, March 8, 2007 1:27PM  1:39PM 
V38.00010: Nonlinearity in the effect of an inhomogeneous Hall angle Daniel W. Koon The differential equation for the electric potential in a conducting material with an inhomogeneous Hall angle is extended to the largefield limit. This equation is solved for a square specimen, using a successive overrelaxation [SOR] technique for matrices of up to 101x101 size, and the Hall weighting function $$ the effect of local pointlike perturbations on the measured Hall angle  is calculated as both the unperturbed Hall angle, $\tan \Theta _H $, and the perturbation, $\delta \tan \Theta _H $, exceed the linear, small angle limit. Preliminary results show that the Hall angle varies by no more than 5{\%} if both $\left {\tan \Theta _H } \right<1$ and $\left {\delta \tan \Theta _H } \right<1$. Thus, previously calculated results for the Hall weighting function can be used for most materials in all but the most extreme magnetic fields. [Preview Abstract] 
Thursday, March 8, 2007 1:39PM  1:51PM 
V38.00011: Electrical measurements of parametric resonance in silicon cantilevers Michael Requa, Kimberly Turner Micro and nano scale mechanical oscillators, in particular cantilevers, show great promise as highly sensitive mass sensors for their small inertial mass and high Qfactors. Sensitivity to environmental factors (force and mass) are limited by theresolution of the resonant frequency measurement in such systems. Experimental investigations to the frequency resolution of bistable nonlinear dynamics for resonators exhibiting parametric resonance have been performed. Using Lorentz interactions for excitation and detection, the all electrical measurements of such oscillations in nonlinear dynamics require nontrivial instrumentation demonstrated in this work. Frequency resolution of 100 parts in 1 billion in vacuum are demonstrated at room temperature suggesting potential enhancements over more conventional harmonic resonant techniques. [Preview Abstract] 
Thursday, March 8, 2007 1:51PM  2:03PM 
V38.00012: Detectors of the Cyrogenic Dark Matter Search: Charge Transport in the ZeroPoint Regime Kyle Sundqvist The Cryogenic Dark Matter Search (CDMS) seeks to detect weaklyinteracting massive particles (WIMPs) in the halo of our galaxy. WIMPs are predicted under supersymmetric particle theory, and are a favored solution to the dark matter problem in cosmology. We will describe how the CDMS experiment measures both the ionized charge and the energy in athermal phonons created by particle interactions in Ge and Si crystals at a temperature of 40 mK. Performing simultaneous measurements in this way creates a signature response for each event. The result offers an unsurpassed ability to discriminate candidate WIMPnucleon interactions from those of radioactive background. Of particular interest to condensed matter physics is a consideration of experimental challenges that arise. Charge collection potentials must remain at only a few volts, else emitted phonons from drifted carriers will dominate the phonons of the original interaction. Also, at this low lattice temperature, we operate in a charge transport regime rarely encountered for lowbias levels; carrier scattering is dominated by the zeropoint fluctuations of the lattice ions. We apply this understanding to chargerelated phenomena seen in our detectors. [Preview Abstract] 
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