IRG 2 FRG 2 – Magnetic Resonance in Organic Semiconductors

Team

Dr. Christoph Boehme (Professor), Research Website
Dr. John Lupton (Professor), Research Website
Dr. Mikhail Raikh (Professor), Research Website
Dr. Brian Saam (Professor), Research Website
Dr. Valy Vardeny (Professor), Research Website
Dr. Clayton Williams (Professor), Research Website
Dr. Sigurd Hӧger (Professor, Univ. of Bonn), Research Website 

Dr. Kipp van Schooten (Post-doctoral Researcher), 

Kapil Ambal (Graduate Student)
Eddie Thennel (Graduate Student)
Tom Paskvan (Undergraduate Student)

Past Members:
Dr. Rob Roundy (Graduate Student),
Dr. Hans Malissa (Post-doctoral Researcher),
Dr. Mark Limes (Graduate Student), Dr. Rachel Glenn (Post-doctoral Researcher, Graduate Student),
Currently in the Mukamel Group at the University of California, Irvine
Dr. William Baker (Post-doctoral Researcher, Graduate Student),
Currently at the Centre for Quantum Computation & Communication Technology at the University of South Wales

Research Overview

The magnetic resonance Focused Research Group explores spin excitations (and their effects) in organic semiconductors, and applies this knowledge to the development of practical devices.
 

Research Objectives and Results

  • -Implement electrically detected electron-nuclear double resonance (ENDOR); acquire preliminary data.

  • -Develop a state-of-the-art user facility for high-field (12 Tesla) electron and nuclear spin manipulation.
    Highfield

    Sketches of the high-field facility showing several major components. Image: Kipp van Schooten

  • -Optimize and scale a recently demonstrated, newly invented organic magnetometer device based on a spintronic effect; find optimal material for this device.
  • Willpic

    An image of a prototype for a microdesign of an organic, thin-film magnetometer.  Image: Shai Vardeny
    Open access article on previous MRSEC work in Nature Communications 3, 898 (2012).

     

  • -Perform analytical calculation of the influence of exchange, hyperfine, and spin-orbit coupling on spin-coherently controlled electric current and optical emission.
    -Perform numerical simulation of the influence of dipolar coupling on spin-coherently controlled electric current and optical emission.
    Raikhpic

    (I.) (a-c) Spectra of the Rabi oscillations in the limit of strong exchange versus dimensionless detuning, for three ratios of dimensionless Rabi frequency, 0.5 (a) 1.75 (b), and 4.0 (c). The thickness of each line represents the corresponding peak intensity. (d) Spectrum of the Rabi oscillations obtained from numerical simulations for a ratio of 0.5 as a function of dimensionless detuning. The line intensities are encoded in the brightness of the curves. Image: Rachel Glenn
    Articles in Physical Review B, 87:165205, (2013), 87:165204, (2013).
    (II.) (a) Current passage through a bipolar device involves recombination of electron (red) and hole (blue)
    which occupy the neighboring sites; (b) Example of a pair in which electron is on-resonance and hole is off-resonance. The bubble illustrates the efficient mixing of the triplet components by the ac field, which, in turn, affects the crossing rate T0 ⇆ S. The gray arrow indicates that recombination occurs exclusively from S. (III.) The evolution of dimensionless decay rates of different modes with amplitude of the ac drive is plotted. (IV.) (a) The evolution of quasienergies with amplitude of the driving field is plotted. (b) Merging of two quasienergies at large Rabi frequency is accompanied by splitting of their widths (c), which is a manifestation of Dicke physics. Images: Robert Roundy
    Article posted in the arXiv, Article 1306.4436.

     

  • -Demonstrate low-field optically detected magnetic resonance in conjugated polymers.
    Lowfield

    Components of a stand-alone low-field optically detection apparatus, including a 405 nm OBIS laser (detection amplifier not shown), home-built electromagnet, and PC controlled ADC, field sweep, and pulse generator.

     

  • -Characterize nuclear spin relaxation in organic semiconductors, as a limit to polarization transfer from the hyperfine interaction.
    DOOPPV

    Preliminary longitudinal relaxation (T1) data for DOO-PPV at a magnetic field of 4.7 T, at a wide range of temperatures. The low relaxation rates at low temperature could allow for a build-up of nuclear polarization due to polarized electrons in devices, made possible through the hyperfine interaction. Image: Eddie Thennel

Capabilities

  • -Multifrequency pulse EPR (Bruker Elxsys E580) spectrometer with ENDOR and ELDOR (electron-electron double resonance) insert, with two self-built low frequency pulsed EDMR/ODMR spectrometers.
  • -Multifrequency two-channel (Tecmag Redstone) NMR spectrometer.
  • -Standard sample preparation glove-box facility.

  • -Photolithography, deposition, and fabrication of inorganic device components through the University of Utah’s Nanofabrication Facility.

  • -A unique self-contained facility to carry out low-temperature single-molecule spectroscopy that is particularly suited for the investigation of systems with a high degree of intramolecular disorder — such as conjugated polymers.