Physics - People Directory: Faculty

Christoph Boehme joined the faculty in January, 2006. His work is centered about the detection of coherent spin motion of extremely small spin ensembles. Traditionally, spin coherence is measured by pulsed magnetic resonance methods (pulsed ESR for electrons, pulsed NMR for nuclei), which is based on the detection of radiation coming out of precessing spins, whose non-energy eigenstates have been prepared by magnetic resonance induced unitary transformations. ESR is the spectroscopy of magnetic field induced Zeeman separations of normally degenerate spin eigenstates of microscopic paramagnetic centers. Zeeman separations are usually small - for X-Band (microwave) excitation its at about 40µeV. Single or small numbers of photons can not be detected at these wavelength. Moreover, polarization of spin ensembles under these conditions is very low. At room temperature, it is less than 10^-4, at T = 5K, it is still less than 5%. Since the number of the emitted photons depends on polarization, another strong limitation is given and thus, the absolute ESR detection limit is in the ranges of 10¹¹ to 10¹² spins which have to be present in the spectrometers if a signal is to be found. This is insufficient for many applications such as the investigation of systems with low spin densities (e.g. highly diluted chemical radicals) or microscopic quasi 2 dimensional systems such as semiconductor surfaces and interfaces. The latter plays a significant role for thin film electronics as used for microelectronics, photovoltaics, display technology etc. but also for physics basic research such as semiconductor based spin quantum information or spintronics research where the coherent measurement of small spin ensembles is important.

Christoph Boehme's work consists of a methodological part where the theoretical and experimental foundations of the coherent small ensemble magnetic resonance spectroscopy are explored as well as an application part where real material systems are investigated. In addition, has also participated to a variety of studies on solar cell technology which are not all related to magnetic resonance and spin detection.

Christoph M. Boehme Assistant Professor Office: 310 JFB Phone: (801) 581-6806 E-mail: boehme"at"physics.utah.edu Homepage	Educational Background:
	Diplom, 2000, Ruprech-Karls-Universität Heidelberg PhD (Dr. rer. nat.), 2003, Philipps-Universität Marburg
	Research Interests:
	Christoph Boehme joined the faculty in January, 2006. His work is centered about the detection of coherent spin motion of extremely small spin ensembles. Traditionally, spin coherence is measured by pulsed magnetic resonance methods (pulsed ESR for electrons, pulsed NMR for nuclei), which is based on the detection of radiation coming out of precessing spins, whose non-energy eigenstates have been prepared by magnetic resonance induced unitary transformations. ESR is the spectroscopy of magnetic field induced Zeeman separations of normally degenerate spin eigenstates of microscopic paramagnetic centers. Zeeman separations are usually small - for X-Band (microwave) excitation its at about 40µeV. Single or small numbers of photons can not be detected at these wavelength. Moreover, polarization of spin ensembles under these conditions is very low. At room temperature, it is less than 10^-4, at T = 5K, it is still less than 5%. Since the number of the emitted photons depends on polarization, another strong limitation is given and thus, the absolute ESR detection limit is in the ranges of 10¹¹ to 10¹² spins which have to be present in the spectrometers if a signal is to be found. This is insufficient for many applications such as the investigation of systems with low spin densities (e.g. highly diluted chemical radicals) or microscopic quasi 2 dimensional systems such as semiconductor surfaces and interfaces. The latter plays a significant role for thin film electronics as used for microelectronics, photovoltaics, display technology etc. but also for physics basic research such as semiconductor based spin quantum information or spintronics research where the coherent measurement of small spin ensembles is important. Christoph Boehme's work consists of a methodological part where the theoretical and experimental foundations of the coherent small ensemble magnetic resonance spectroscopy are explored as well as an application part where real material systems are investigated. In addition, has also participated to a variety of studies on solar cell technology which are not all related to magnetic resonance and spin detection.
	Selected Recent Publications
	The investigation of charge carrier recombination and hopping transport with pulsed electrically detected magnetic resonance techniques (with Klaus Lips); article in the book: "Charge transport in disordered solids with applications in electronics", edited by Sergei Baranovski, published by Whiley (2006). The ultra–sensitive electrical detection of spin Rabi oscillation at paramagnetic defects (with Klaus Lips); e-archive: quant-ph: 0509120 (2005). Triplet recombination at P_b centers and its implications for capture cross sections (with Felice Friedrich and Klaus Lips); J. Appl. Phys. 97, 056101 (2005). - Link The impact of the electron spin on charge carrier recombination – the example of amorphous silicon (with Takashi Ehara and Klaus Lips); Journal of Optoelectronics and Advanced Materials, 7, (1) 13 – 24 (2005). - Link Electrical detection of spin coherence in silicon (with Klaus Lips); Phys. Rev. Lett., 91 (24), 246603 (2003). - Link Theory of the time–domain measurement of spin–dependent recombination with pulsed electrically detected magnetic resonance (with Klaus Lips); Phys. Rev. B, 68 (24), 245105 (2003). - Link Dynamics of spin-dependent charge carrier recombination; Cuvillier Verlag (Publisher), Göttingen (2003). - Link Time domain measurement of spin-dependent recombination (with Klaus Lips); Appl. Phys. Lett., 79 (26), 4363 (2001). - Link Quantum-beat recombination echoes (with Peter Kanschat and Klaus Lips); Europhys. Lett., 56 (5), 716 (2001). - Link H loss mechanism during anneal of silicon nitride: Chemical dissociation (with Gerald Lucovsky); J. Appl. Phys., 88 (10), 6055 (2000). - Link