University of Minnesota
School of Physics & Astronomy

Condensed Matter Seminar

Thursday, January 31st 2008
1:25 pm:
Condensed Matter Seminar in 210 Physics
Speaker: Speaker: Dr. M. Poggio, IBM Almaden Research Center
Subject: Ultrasensitive force detection applied to nuclear magnetic resonance

Magnetic resonance imaging (MRI) is a powerful technique that typically
operates on the scale of millimeters to micrometers. Conventional MRI is
based on the manipulation of nuclear spins with radio-frequency fields and
the subsequent detection of spins with induction-based techniques. An
alternative approach, magnetic resonance force microscopy (MRFM), uses force
detection to overcome the sensitivity limitations of conventional MRI.
Recently we demonstrated that two-dimensional imaging of nuclear spins can
be extended to a spatial resolution better than 100 nm using MRFM [1]. We
have since made even greater strides in the process of imaging nanoscale
biological samples, achieving a three-dimensional resolution better than 10
nm. These results both demonstrate the feasibility of MRI on the nanoscale
and the applicability of MRFM to image biologically relevant samples.

If we are to further improve this resolution in order to eventually image on
the scale of single nuclear spins, the force sensitivity of the measurement
must be improved by roughly 2 orders of magnitude. In this talk I will
discuss some work done in pursuit of this goal including the application of
force detection techniques to do nanoscale MRI [1], the cooling of
mechanical oscillator modes to millikelvin temperatures using feedback [2],
and the design of nanoelectronic and nanomechanical devices to improve spin
detection sensitivity [3]. I will also discuss the manipulation of
statistically polarized spin ensembles [4] and our recent experiments using
MRFM to image single tobacco mosaic virus (TMV) particles.

[1] H. J. Mamin, M. Poggio, C. L. Degen, and D. Rugar, Nature Nanotech. 2,
301 (2007).
[2] M. Poggio, C. L. Degen, H. J. Mamin, and D. Rugar, Phys. Rev. Lett. 99,
017201 (2007).
[3] M. Poggio, C. L. Degen, C. T. Rettner, H. J. Mamin, and D. Rugar, Appl.
Phys. Lett. 90, 263111 (2007).
[4] C. L. Degen, M. Poggio, H. J. Mamin, and D. Rugar, Phys. Rev. Lett. 99,
250601 (2007).

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