Bulletin of the American Physical Society
2012 Annual Fall Meeting of the APS Prairie Section
Volume 57, Number 14
Thursday–Saturday, November 8–10, 2012; Lawrence, Kansas
Session C2: Condensed Matter Physics II |
Hide Abstracts |
Chair: Hsin-Ying Chiu, University of Kansas Room: Oread Hotel Griffith Room |
Friday, November 9, 2012 2:00PM - 2:35PM |
C2.00001: Theory of single-spin dynamics for transition-metal dopants in diamond Invited Speaker: Michael Flatt\'e Spin centers in diamond, especially the well-studied nitrogen-vacancy center, exhibit exceptionally favorable properties for quantum control, including remarkably long room temperature spin coherence times, optical excitation, manipulation by RF fields and optical readout. Although transition-metal dopants in diamond have not been as extensively studied, they offer novel opportunities for external control of single-spin dynamics by comparison, which originate from the symmetry of the dopant's d shell in a tetrahedral lattice and the presence of strong spin-orbit coupling. The d-shell states of a substitutional transition-metal dopant can be either strongly hybridized with the diamond host electronic structure (t2 symmetry states) or very weakly hybridized (e symmetry states) due to a mismatch of the symmetry of the states of the dopant and host. Thus the electronic wave function of the spin-1 ground state of a dopant like Cr is atomic-like and unresponsive to external perturbations of the lattice or an applied electric field. Ni, which also has a spin-1 ground state, has strongly hybridized electronic wave functions and is sensitive to local strain and electric fields. The more extended states that produce the Ni ground state spin provide helpful consequences for spin manipulation. The ground state of Ni is found to behave as a spin-1/2 predominately on the Ni site and a ferromagnetically-oriented spin-1/2 predominately on the four nearest-neighbor carbon sites around the Ni. Under compressive hydrostatic strain the overlap between these two wave functions increases and a transition can be reached where the two spins orient antiferromagnetically; a similar effect is seen in double quantum dots where it has been used to perform exchange-only quantum operations on a qubit composed of the two-electron spin singlet and the zero-magnetization two-electron spin triplet. We propose use of the same effect for strain-mediated control of encoded qubits in diamond. [Preview Abstract] |
Friday, November 9, 2012 2:35PM - 2:47PM |
C2.00002: Evidence for the Collective Nature of the Reentrant Integer Quantum Hall States of the Second Landau Level Ashwani Kumar, Nianpei Deng, Michael Manfra, Loren Pfeiffer, Ken West, Gabor Csathy At low temperatures and in the presence of magnetic field, high quality two dimensional electron systems exhibit exotic states of matter such as fractional quantum states and the reentrant integer quantum Hall states (RIQHS). In this presentation we report a systematic study of RIQHS in the second Landau level. We observed an unexpected sharp peak in the temperature dependence of the magnetoresistance of the RIQHSs. This peak defines the onset temperature of these states. We find that in different spin branches the onset temperatures of the reentrant states scale with the Coulomb energy. This scaling provides direct evidence that Coulomb interactions play an important role in the formation of these reentrant states evincing their collective nature. [Preview Abstract] |
Friday, November 9, 2012 2:47PM - 2:59PM |
C2.00003: The effect of spin fluctuations on scattering rates in diluted magnetic semiconductors Matthew Mower, Giovanni Vignale We study the scattering rate of carriers due to large spin fluctuations in diluted magnetic semiconductors near the ferromagnetic transition. Both the carrier-impurity and carrier-carrier scattering rates are considered. We calculate an enhancement of the carrier resistivity when crossing from the paramagnetic to ferromagnetic regimes. The enhanced resistivity has a noticeable impact on spin lifetimes from the Dyakonov-Perel and Elliott-Yafet spin relaxation mechanisms. [Preview Abstract] |
Friday, November 9, 2012 2:59PM - 3:11PM |
C2.00004: Protein folding intermediates probed by ensemble of their transient stiffnesses in single-molecule force-quenched AFM Robert Szoszkiewicz, Katarzyna Malek By using force-quench AFM (FQ-AFM) spectroscopy molecular structures with transient stiffnesses are detected during folding of a recombinant protein with four I27 molecules linked in tandem. The intermediate stiffnesses are detected from shape and peaks of the autocorrelation of fluctuations in end-to-end lengths of the folding molecules, as well as by applying the equipartition theorem to the FQ-AFM experimental results. In the light of the relevant molecular dynamics simulations these intermediates are likely to probe the ensemble of random-coiled collapsed states present both in the force-quench and thermal-quench folding pathways. [Preview Abstract] |
Friday, November 9, 2012 3:11PM - 3:23PM |
C2.00005: Substrate effect on few-layer MoS2 transistors Jatinder Kumar, Hui-Chun Chien, Hsin-Ying Chiu Due to the realization of graphene transistors but without applicable bandgap, the similar layered structure molybdenum disulfide (MoS2) field effect transistors with nonzero bandgap have been demonstrated and reveal promising potential. Previous experiments showed that carrier mobility could be enhanced by depositing hafnium dioxide (HfO2) on top of MoS2 devices, which was possibly attribute to the suppression of Coulomb scattering by high-$\kappa$ environment and surface polar phonon scattering. In our talk, we will present the electrical transport experiments in few layers of MoS2 on HfO2 dielectrics, including the carrier mobility improvement and electrical transport phenomena in high bias region. [Preview Abstract] |
Friday, November 9, 2012 3:23PM - 3:35PM |
C2.00006: Using Atomic Layer Deposition for Josephson Junction Quantum Bits Alan Elliot, Gary Malek, Rongtao Lu, Siyuan Han, Judy Wu, H.F. Yu, G.M. Xue, S.P. Zhao Ultrathin dielectric tunneling barriers are critical to Josephson junction (JJ) based superconducting quantum bits (qubits). However, the prevailing technique of thermally oxidizing aluminum via oxygen diffusion produces problematic point defects, such as oxygen vacancies, which are believed to be a primary source of the two-level fluctuators that contribute to the decoherence of the qubits. Atomic Layer Deposition (ALD) of aluminum oxide (Al$_{2}$O$_{3})$ is a promising alternative to resolve the issue of oxygen vacancies in the Al$_{2}$O$_{3\, }$tunneling barrier, and its self-limiting growth mechanism provides atomic-scale precision in tunneling barrier thickness control. ALD has been implemented in a high-vacuum magnetron sputtering system for \textit{in situ} deposition of ALD-Al$_{2}$O$_{3}$ tunneling barriers in superconductor-insulator-superconductor (SIS) JJs. The modifications made to the Al surface during ALD were explored with ellipsometry and atomic force microscopy, and ALD-Al$_{2}$O$_{3}$ barriers were grown on Nb to form Nb/Al2O3/Nb JJs. Preliminary low temperature measurements of current-voltage characteristics of the Josephson junctions made from these trilayers confirmed the integrity of the ALD-Al$_{2}$O$_{3}$ barrier layer. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700