Dissertation Abstracts
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DATABASE: Diss                          LIMITED TO:
SEARCH: su:quantum interference FOUND 213 Records
 
 ____NO.__AUTHOR______________TITLE______________________________________YEAR
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|     1   SHAO, ZHI-AN        TRANSMISSION RESONANCES AND ANTIRESONANCE  1994
|     2   BERRY, MICHAEL JAM  MESOSCOPIC TRANSPORT AND QUANTUM CHAOS IN  1994
|     3   LADDHA, SHASHI      ROOM TEMPERATURE AGING AND MAGNETOMECHANI  1994
|     4   VAN DEN BERGH, MAG  QUANTUM OPTISCHE BESCHOUWINGEN VOOR GAMMA  1994
|     5   LINNERUD, IVAR      MANY-BODY EFFECTS AND OPTICAL PROPERTIES   1994
|     6   WEERSINK, ROBERT A  INTRAMOLECULAR AND INTERMOLECULAR DYNAMIC  1994
|     7   HU, XUELONG         A STUDY OF A TWO-DIMENSIONAL ELECTRON SYS  1994
|     8   HUANG, JIAMING      QUANTUM INTERFERENCE EFFECTS IN MESOSCOPI  1994

SEARCH: su:quantum interference
 
 Record  1 of  213__________________________________________(Page  1 of  6)
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|ACCESSION NO.:  AAI9516636
|        TITLE:  TRANSMISSION RESONANCES AND ANTIRESONANCES IN QUANTUM
|                WAVEGUIDE SYSTEMS WITH ATTACHED RESONATORS AND THEIR DEVICE
|                APPLICATIONS
|       AUTHOR:  SHAO, ZHI-AN
|       DEGREE:  PH.D.
|         YEAR:  1994
|  INSTITUTION:  UNIVERSITY OF NOTRE DAME; 0165
|      ADVISER:  Director: WOLFGANG POROD
|       SOURCE:  DAI, VOL. 56-01B, Page 0439, 00172 Pages
|  DESCRIPTORS:  ENGINEERING, ELECTRONICS AND ELECTRICAL
|     ABSTRACT:  Much work has been done for transmission in quantum
|                waveguide systems. By examining the transmission amplitude
|                in the complex-energy plane, it is found that, similar to
|                double-barrier resonant tunneling, there are transmission
|                poles in the complex-energy plane for these systems which
|                contain quasi-bound states in attached resonators. In
|                contrast to double-barrier resonant tunneling, it is also
|                found that these systems possess transmission zeros. The
|                existence of transmission zeros is a characteristic feature
|                of quantum waveguide structures with attached resonators,
|                but is absent for double-barrier resonant tunneling. Each
|                quasi-bound state of the resonator leads to a zero-pole pair
|                of the transmission amplitude in the complex-energy plane.
|                The resonance-antiresonance behavior of the transmission on
|                the real-energy axis can be understood in terms of these
|                zero-pole pairs.
|                The resonance-antiresonance feature is also discussed in the
|                context of Fano resonances, which are known to occur when
|                two scattering channels are available. Its line shape is
|                investigated based on the zero-pole nature, and a
|                generalization of the familiar Lorentzian line shape has
|                been found. Global fits for the transmission probability are
|                also studied. A resonance formalism for symmetrical multi-
|                barrier systems is proposed and excellent fits are obtained.
|                Based on the resonance-antiresonance feature, two new
|                negative differential resistance devices are proposed. One
|                of them is designed by inserting a resonant cavity in the
|                well region of the double-barrier structure. Another one is
|                designed by weakening the coupling between the cavity and
|                the channel in a t-stub tuner. In both devices, the quantum
|                interference effect in the cavity leads to the perfect
|                transmission modulation, which may help to improve the
|                current peak-to-valley ratio.
|                A numerical technique, which can be used to calculate the
|                quasi-bound states of resonant transmitting systems, is
|                presented. The transmission problem is an inhomogeneous
|                problem. Forcing the source term to zero, the inhomogeneous
|                problem changes to a homogeneous problem. Using the finite
|                element method, this homogeneous problem is a linear
|                eigenvalue problem. This eigenvalue method also can be used
|                to calculate the positions of transmission zeros and ones.


 Record 14 of  213__________________________________________(Page  1 of  6)
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|ACCESSION NO.:  AAG9504918
|        TITLE:  LOW-FREQUENCY NOISE IN HIGH-T(C) SUPERCONDUCTOR JOSEPHSON
|                JUNCTIONS, SQUIDS, AND MAGNETOMETERS
|       AUTHOR:  MIKLICH, ANDREW HOSTETLER
|       DEGREE:  PH.D.
|         YEAR:  1994
|  INSTITUTION:  UNIVERSITY OF CALIFORNIA, BERKELEY; 0028
|      ADVISER:  Chair: JOHN CLARKE
|       SOURCE:  DAI, VOL. 55-09B, Page 3958, 00133 Pages
|  DESCRIPTORS:  PHYSICS, SOLID STATE; PHYSICS, ELECTRONICS AND ELECTRICITY;
|                ENGINEERING, ELECTRONICS AND ELECTRICAL
|     ABSTRACT:  The design and performance of high-T$sb0rm c$ dc
|                superconducting quantum interference devices (SQUIDs), the
|                junctions that comprise them, and magnetometers made from
|                them are described, with special attention paid to sources
|                of 1/f noise. Biepitaxial junctions are found to have large
|                levels of critical current fluctuations which make them
|                unsuitable for low-noise SQUIDs. This noise suggests a
|                poorly connected interface at the grain boundary junction.
|                SQUIDs from bicrystal junctions, in contrast, have levels of
|                critical current noise that are controllable using bias
|                current reversal techniques which leave the noise white down
|                to frequencies of a few Hz. A SQUID with an energy
|                resolution of $1.5times 10sp0-30$ J Hz$sp0-1$ at 1 Hz is
|                reported. Magnetometers in which a (9 mm)$sp2$ pickup loop
|                is directly coupled to a SQUID body have achieved field
|                resolutions of 93 fT Hz$sp0-1/2$ down to frequencies below 1
|                Hz, improving to 39 fT Hz$sp0-1/2$ at 1 Hz with the addition
|                of a 50 mm-diameter single-turn flux transformer. Although
|                the performance of these devices is sufficient for single-
|                channel biomagnetometry or geophysical studies, their
|                relatively poor coupling to the pickup loop makes it
|                difficult to satisfy the competing goals of high field
|                resolution and small detector size necessary for
|                multichannel biomagnetic imaging. Improved coupling is
|                demonstrated by the use of multiturn-input-coil flux
|                transformers, and a resolution of 35 fT Hz$sp0-1/2$ in the
|                white noise region is reported with a (10 mm)$sp2$ pickup
|                loop. However, additional 1/f noise from the processed
|                multilayer structures in the transformer limits the
|                resolution at 1 Hz to 114 fT Hz$sp0-1/2$. High-T$sb0rm c$
|                SQUIDs are shown to exhibit additional 1/f noise when they
|                are cooled in a nonzero static magnetic field because of the
|                additional flux vortices trapped in the film, with the noise
|                power at 1 Hz typically increasing by a factor of 10-20 in a
|                field of 0.05 mT (0.5 G). Finally, a SQUID-based voltmeter
|                with a resolution of 9.2 pV Hz$sp0-1/2$ at 10 Hz (24 pV
|                Hz$sp0-1/2$ at 1 Hz) is described.

DATABASE: Diss                          LIMITED TO:
SEARCH: su:squid FOUND 303 Records
 
 ____NO.__AUTHOR______________TITLE______________________________________YEAR
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|     1   VISWANATHAN, HEMA   FLUX PINNING AND CRITICAL CURRENT DENSITI  1994
|     2   BORTONE DI MURO, E  EVALUATION OF VEGETABLE PROTEIN MIXTURES   1994
|     3   CHOI, SIYOUNG       SYNTHESIS AND MAGNETIC PROPERTIES OF ZIRC  1994
|     4   PAVLOSKY, MARK ALA  SPECTROSCOPIC STUDIES OF THE NON-HEME IRO  1995
|     5   LADDHA, SHASHI      ROOM TEMPERATURE AGING AND MAGNETOMECHANI  1994
|     6   IJSSELSTEIJN, ROBB  LASER DEPOSITED HIGH CRITICAL TRANSITION   1994
|     7   WILBY, PHILIP RICH  THE MECHANISMS AND TIMING OF MINERALIZATI  1994
|     8   LEE, SHANG-FAN      PERPENDICULAR RESISTANCE AND MAGNETORESIS  1994

 Record  1 of  303__________________________________________(Page  1 of  5)
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|ACCESSION NO.:  AAI9523458
|        TITLE:  FLUX PINNING AND CRITICAL CURRENT DENSITIES IN PROTON
|                IRRADIATED SINGLE CRYSTAL YTTRIUM BARIUM COPPER OXIDE
|       AUTHOR:  VISWANATHAN, HEMA KRISHNAN
|       DEGREE:  PH.D.
|         YEAR:  1994
|  INSTITUTION:  PURDUE UNIVERSITY; 0183
|      ADVISER:  Major Professor: RONALD REIFENBERGER
|       SOURCE:  DAI, VOL. 56-02B, Page 0901, 00129 Pages
|  DESCRIPTORS:  PHYSICS, SOLID STATE
|     ABSTRACT:  Radiation damage has been traditionally used to introduce
|                artificial pinning centers into superconducting material in
|                order to enhance their critical current densities. The
|                objective of this study was to determine the effect of
|                defects induced by irradiation with 3.5 MeV protons on the
|                critical current densities and to investigate the structure
|                of the defects using SQUID magnetization and
|                magnetoresistive measurements.
|                There are three general types of defects produced by proton
|                irradiation at room temperature. They are (1) a relatively
|                high concentration of point defects on all the sublattices,
|                (2) clusters of point defects, and (3) the defect cascades.
|                SQUID magnetization measurements suggest that the defect
|                clusters and cascades are effective in pinning the vortices
|                at 70 K for $vec0rm HVertvec0rm c$ axis. Additional
|                contribution to pinning at 10 K for $vec0rm HVertvec0rm c$
|                axis comes from the vacancies formed upon irradiation with
|                protons. The defect clusters seem to be the only
|                contributors to pinning for $vec0rm HVertvec0rm ab$ plane.
|                The anisotropy of the critical current densities in
|                detwinned crystals between field orientations parallel to
|                the $vec0rm a$ and $vec0rm b$ axes determined from
|                magnetization measurements at 10 K consistently show that
|                $rm Jsbsp0c0c(vec HVertvec b)>Jsbsp0c0c(vec HVertvec a)$ at
|                all fields after 2 irradiations and annealing for 2 and 4
|                weeks.
|                The effect of proton irradiation on the resistive transition
|                and the anisotropy of the defect structure was studied using
|                angular dependence of the resistivity in $rm
|                YBasb2Cusb3Osb07-delta$ single crytals. The expected drop in
|                resistivity when the field is aligned parallel to the
|                $vec0rm c$ axis due to the alignment of the vortices with
|                the defect cluster as observed in the case of the twin
|                boundaries was absent.
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