Dissertations / Theses: 'Mesoscopic phenomena (Physics)'

1

蔡福陽 and Fuk-yeung Tsoi. "Persistent currents in Anderson-Hubbard mesoscopic rings." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31223539.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Tsoi, Fuk-yeung. "Persistent currents in Anderson-Hubbard mesoscopic rings /." Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21490120.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Golod, Taras. "Mesoscopic phenomena in hybrid superconductor/ferromagnet structures." Doctoral thesis, Stockholms universitet, Fysikum, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-56629.

Full text

Abstract:

This thesis explores peculiar effects of mesoscopic structures revealed at low temperatures. Three particular systems are studied experimentally: Ferromagnetic thin films made of diluted Pt1-xNix alloy, hybrid nanoscale Nb-Pt1-xNix-Nb Josephson junctions, and planar niobium Josephson junction with barrier layer made of Cu or Cu0.47Ni0.53 alloy. A cost-effective way is applied to fabricate the sputtered NixPt1-x thin films with controllable Ni concentration. 3D Focused Ion Beam (FIB) sculpturing is used to fabricate Nb-Pt1-xNix-Nb Josephson junctions. The planar junctions are made by cutting Cu-Nb or CuNi-Nb double layer by FIB. Magnetic properties of PtNi thin films are studied via the Hall effect. It is found that films with sub-critical Ni concentration are superparamagnetic at low temperatures and exhibit perpendicular magnetic anisotropy. Films with over-critical Ni concentration are ferromagnetic with parallel anisotropy. At the critical concentration the films demonstrate canted magnetization with the easy axis rotating as a function of temperature. The magnetism appears via two consecutive crossovers, going from paramagnetic to superparamagnetic to ferromagnetic, and the extraordinary Hall effect changes sign at low temperatures. Detailed studies of superconductor-ferromagnet-superconductor Josephson junctions are carried out depending on the size of junction, thickness and composition of the ferromagnetic layer. The junction critical current density decreases non-monotonically with increasing Ni concentration. It has a minimum at ~ 40 at.% of Ni which indicates a switching into the π state. The fabricated junctions are used as phase sensitive detectors for analysis of vortex states in mesoscopic superconductors. It is found that the vortex induces different flux shifts, in the measured Fraunhofer modulation of the Josephson critical current, depending on the position of the vortex. When the vortex is close to the junction it induces a flux shift equal to Φ0/2 leading to switching of the junction into the 0-π state. By changing the bias current at constant magnetic field the vortices can be manipulated and the system can be switched between two consecutive vortex states. A mesoscopic superconductor can thus act as a memory cell in which the junction is used both for reading and writing information (vortex).

APA, Harvard, Vancouver, ISO, and other styles

4

Zelyak, Oleksandr. "Persistent Currents and Quantum Critical Phenomena in Mesoscopic Physics." UKnowledge, 2009. http://uknowledge.uky.edu/gradschool_diss/723.

Full text

Abstract:

In this thesis, we study persistent currents and quantum critical phenomena in the systems of mesoscopic physics. As an introduction in Chapter 1 we familiarize the reader with the area of mesoscopic physics. We explain how mesoscopic systems are different from quantum systems of single atoms and molecules and bulk systems with an Avogadro number of elements. We also describe some important mesoscopic phenomena. One of the mathematical tools that we extensively use in our studies is Random Matrix Theorty. This theory is not a part of standard physics courses and for educational purposes we provide the basics of Random Matrix Theory in Chapter 2. In Chapter 3 we study the persistent current of noninteracting electrons in quantum billiards. We consider simply connected chaotic Robnik-Berry quantum billiard and its annular analog. The electrons move in the presence of a point-like magnetic flux at the center of the billiard. For the simply connected billiard, we find a large diamagnetic contribution to the persistent current at small flux, which is independent of the flux and is proportional to the number of electrons (or equivalently the density since we keep the area fixed). The size of this diamagnetic contribution is much larger than the previously studied mesoscopic fluctuations in the persistent current in the simply connected billiard. This behavior of persistent current can ultimately be traced to the response of the angular-momentum l = 0 levels (neglected in semiclassical expansions) on the unit disk to a point-like flux at its center. We observe the same behavior for the annular billiard when the inner radius is much smaller than the outer one. We also find that the usual fluctuating persistent current and Anderson-like localization due to boundary scattering are seen when the annulus tends to a one-dimensional ring. We explore the conditions for the observability of this phenomenon. In Chapter 4 we study quantum critical phenomena in a system of two coupled quantum dots connected by a hopping bridge. Both the dots and connecting region are assumed to be in universal Random Matrix crossover regimes between Gaussian orthogonal and unitary ensembles (defined in Chapter 2). We exploit a diagrammatic approach appropriate for energy separations much larger than the level spacing, to obtain the ensemble-averaged one- and two-particle Greens functions. We find that two main components of the twoparticle Green’s function (diffuson and Cooperon) can be described by separate scaling functions. We then use this information to investigate a model interacting system in which one dot has an attractive s-wave reduced Bardeen-Cooper-Schrieffer interaction, while the other is noninteracting but subject to an orbital magnetic field. We find that the critical temperature TC of the mean-field transition into the superconducting state in the first dot is non-monotonic in the flux through the second dot in a certain regime of interdot coupling. Likewise, the fluctuation magnetization above the critical temperature is also non-monotonic in this regime, can be either diamagnetic or paramagnetic, and can be deduced from the Cooperon scaling function. We end this thesis with conclusion in Chapter 5.

APA, Harvard, Vancouver, ISO, and other styles

5

Matthews, Jason E. "Thermoelectric and Heat Flow Phenomena in Mesoscopic Systems." Thesis, University of Oregon, 2011. http://hdl.handle.net/1794/12108.

Full text

Abstract:

xvii, 189 p. ： ill. (some col.) Low-dimensional electronic systems, systems that are restricted to single energy levels in at least one of the three spatial dimensions, have attracted considerable interest in the field of thermoelectric materials. At these scales, the ability to manipulate electronic energy levels offers a great deal of control over a device's thermopower, that is, its ability to generate a voltage due to a thermal gradient. In addition, low-dimensional devices offer increased control over phononic heat flow. Mesoscale geometry can also have a large impact on both electron and phonon dynamics. Effects such as ballistic transport in a two-dimensional electron gas structure can lead to the enhancement or attenuation of electron transmission probabilities in multi-terminal junctions. The first half of this dissertation investigates the transverse thermoelectric properties of a four-terminal ballistic junction containing a central symmetry-breaking scatterer. It is believed that the combined symmetry of the scatterer and junction is the key component to understanding non-linear and thermoelectric transport in these junctions. To this end, experimental investigations on this type of junction were carried out to demonstrate its ability to generate a transverse thermovoltage. To aid in interpreting the results, a multi-terminal scattering-matrix theory was developed that relates the junction's non-linear electronic properties to its thermoelectric properties. The possibility of a transverse thermoelectric device also motivated the first derivation of the transverse thermoelectric efficiency. This second half of this dissertation focuses on heat flow phenomena in InAs/InP heterostructure nanowires. In thermoelectric research, a phononic heat flow between thermal reservoirs is considered parasitic due to its minimal contribution to the electrical output. Recent experiments involving heterostructure nanowires have shown an unexpectedly large heat flow, which is attributed in this dissertation to an interplay between electron-phonon interaction and phononic heat flow. Using finite element modeling, the recent experimental findings have provided a means to probe the electron-phonon interaction in InAs nanowires. In the end, it is found that electron-phonon interaction is an important component in understanding heat flow at the nanoscale. This dissertation includes previously unpublished co-authored material. Committee in charge: Dr. Richard Taylor， Chair； Dr. Heiner Linke， Advisor； Dr. David Cohen， Member； Dr. John Toner， Member； Dr. David Johnson， Outside Member

APA, Harvard, Vancouver, ISO, and other styles

6

Lui, Chi-keung Arthur. "Transport properties of hybrid mesoscopic systems." Click to view the E-thesis via HKUTO, 2004. http://sunzi.lib.hku.hk/hkuto/record/B30727339.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Lui, Chi-keung Arthur, and 呂智強. "Transport properties of hybrid mesoscopic systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B30727339.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Zhabinskaya, Dina. "Non-equilibrium phenomena implemented at a mesoscopic time scale." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80902.

Full text

Abstract:

The purpose of this project is to develop an algorithm that speeds up large scale simulations of many-body systems. A numerical method is implemented that simulates non-equilibrium phenomena on a mesoscopic time scale. A system is perturbed by an external force, and time averages of variables renormalized in space are calculated numerically, using results of linear response theory, as the system relaxes to equilibrium. The coarse-grained variables evolve slowly in time, allowing one to advance them on a mesoscopic time scale. The algorithm was tested on two physical systems: a lattice confined ferromagnetic Ising model and an off-lattice Argon-like molecular system. The method simulated accurately the non-equilibrium phenomena studied. It was found that the algorithm is most efficient when it is applied to a process occurring on at least two time scales. This allows one to integrate out the fast, microscopic time scale in order to study long-time, macroscopic behaviour. Through the study of diffusion in a molecular system, it was concluded that the proposed method is computationally faster than solving the microscopic equations of motion and more accurate than solving the macroscopic equations.

APA, Harvard, Vancouver, ISO, and other styles

9

Zarbo, Liviu. "Mesoscopic spin Hall effect in semiconductor nanostructures." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 199 p, 2007. http://proquest.umi.com/pqdweb?did=1397915111&sid=21&Fmt=2&clientId=8331&RQT=309&VName=PQD.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Shangguan, Minhui. "Charge and spin transport in mesoscopic systems." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B39557583.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Shangguan, Minhui, and 上官敏慧. "Charge and spin transport in mesoscopic systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39557583.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Zhao, Xuean. "Electrochemical capacitance in a mesoscopic structure /." Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20978716.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Maldonado, Miguel. "Fabrication of mesoscopic semiconductor devices and their transport characteristics." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/15006.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Scherbakov, Andrew Germanovich. "Transport and thermodynamic properties of mesoscopic quantum systems." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/30384.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Qiao, Zhenhua, and 喬振華. "Charge and spin transport in two-dimensional mesoscopic systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42182281.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Qiao, Zhenhua. "Charge and spin transport in two-dimensional mesoscopic systems." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B42182281.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Xu, Fuming, and 许富明. "Quantum transport study of mesoscopic systems and nanostructures." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B4691772X.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Wang, Baigeng. "General gauge invariant theory of transport in mesoscopic systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31239390.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

郭榮忠 and Wing-chung Kwok. "Current conserving AC quantum transport in two-dimensional mesoscopic systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B3122104X.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Kwok, Wing-chung. "Current conserving AC quantum transport in two-dimensional mesoscopic systems /." Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20668065.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Li, Jian. "Spin transport in mesoscopic systems with spin-orbit coupling." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B39794015.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

Li, Jian, and 李牮. "Spin transport in mesoscopic systems with spin-orbit coupling." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B39794015.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Purbach, Ulrich. "Electron transport in mesoscopic metallic structures /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Sloggett, Clare Physics Faculty of Science UNSW. "Electron correlations in mesoscopic systems." Awarded by:University of New South Wales. School of Physics, 2007. http://handle.unsw.edu.au/1959.4/31875.

Full text

Abstract:

This thesis deals with electron correlation effects within low-dimensional, mesoscopic systems. We study phenomena within two different types of system in which correlations play an important role. The first involves the spectra and spin structure of small symmetric quantum dots, or &quoteartificial atoms&quote. The second is the &quote0.7 structure&quote, a well-known but mysterious anomalous conductance plateau which occurs in the conductance profile of a quantum point contact. Artificial atoms are manufactured mesoscopic devices: quantum dots which resemble real atoms in that their symmetry gives them a &quoteshell structure&quote. We examine two-dimensional circular artificial atoms numerically, using restricted and unrestricted Hartree-Fock simulation. We go beyond the mean-field approximation by direct calculation of second-order correlation terms; a method which works well for real atoms but to our knowledge has not been used before for quantum dots. We examine the spectra and spin structure of such dots and find, contrary to previous theoretical mean-field studies, that Hund's rule is not followed. We also find, in agreement with previous numerical studies, that the shell structure is fragile with respect to a simple elliptical deformation. The 0.7 structure appears in the conductance of a quantum point contact. The conductance through a ballistic quantum point contact is quantised in units of 2e^2/h. On the lowest conductance step, an anomalous narrow conductance plateau at about G = 0.7 x 2e^2/h is known to exist, which cannot be explained in the non-interacting picture. Based on suggestive numerical results, we model conductance through the lowest channel of a quantum point contact analytically. The model is based on the screening of the electron-electron interaction outside the QPC, and our observation that the wavefunctions at the Fermi level are peaked within the QPC. We use a kinetic equation approach, with perturbative account of electron-electron backscattering, to demonstrate that these simple features lead to the existence of a 0.7-like structure in the conductance. The behaviour of this structure reproduces experimentally observed features of the 0.7 structure, including the temperature dependence and the behaviour under applied in-plane magnetic fields.

APA, Harvard, Vancouver, ISO, and other styles

25

Tanaka, Kaori. "Shell structure and classical orbits in mesoscopic systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ30172.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

26

Liu, Xiya. "Mesoscopic effects in ferromagnetic materials." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24669.

Full text

Abstract:

Thesis (Ph.D.)--Physics, Georgia Institute of Technology, 2008. Committee Chair: Davidovic, Dragomir; Committee Member: Citrin, David; Committee Member: Kindermann, Markus; Committee Member: Marchenkov, Alexei; Committee Member: Riedo, Elisa

APA, Harvard, Vancouver, ISO, and other styles

27

Zhou, Fei. "Coherence effects in mesoscopic systems /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/9787.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Martin, Theodore Peyton. "Low-dimensional electron transport in mesoscopic semiconductor devices /." view abstract or download file of text, 2006. http://proquest.umi.com/pqdweb?did=1280149921&sid=2&Fmt=2&clientId=11238&RQT=309&VName=PQD.

Full text

Abstract:

Thesis (Ph. D.)--University of Oregon, 2006. Typescript. Includes vita and abstract. Includes bibliographical references (leaves 187-196). Also available for download via the World Wide Web; free to University of Oregon users.

APA, Harvard, Vancouver, ISO, and other styles

29

Xu, Fuming, and 許富明. "The distribution and fluctuation of electrochemical capacitance in mesoscopic systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B41508737.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Xu, Fuming. "The distribution and fluctuation of electrochemical capacitance in mesoscopic systems." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B41508737.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

趙學安 and Xuean Zhao. "Electrochemical capacitance in a mesoscopic structure." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31239778.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Cui, Ping. "Quantum dissipation theory and applications to quantum transport and quantum measurement in mesoscopic systems /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202006%20CUI.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

鄭蔚 and Wei Zheng. "Dynamic conductance of nanostructures." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B31243939.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Zheng, Wei. "Dynamic conductance of nanostructures /." Hong Kong : University of Hong Kong, 2002. http://sunzi.lib.hku.hk/hkuto/record.jsp?B24367382.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

姚正康 and Ching-hong Yiu. "Time dependent study of quantum transport in mesoscopic systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1997. http://hub.hku.hk/bib/B3121485X.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Yiu, Ching-hong. "Time dependent study of quantum transport in mesoscopic systems /." Hong Kong : University of Hong Kong, 1997. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19471476.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

朱詩亮 and Shiliang Zhu. "Geometric phase and quantum transport in mesoscopic systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B3014775X.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

朱建新 and Jianxin Zhu. "Quantum transport in mesoscopic normal and superconducting systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1997. http://hub.hku.hk/bib/B31236443.

Full text

Abstract:

The Best PhD Thesis in the Faculties of Dentistry, Engineering, Medicine and Science (University of Hong Kong), Li Ka Shing Prize,1995-1997 published_or_final_version Physics Doctoral Doctor of Philosophy

APA, Harvard, Vancouver, ISO, and other styles

39

Zhu, Shiliang. "Geometric phase and quantum transport in mesoscopic systems." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B22956268.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Zhu, Jianxin. "Quantum transport in mesoscopic normal and superconducting systems /." Hong Kong : University of Hong Kong, 1997. http://sunzi.lib.hku.hk/hkuto/record.jsp?B18037471.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

鄭慶榮 and Qingrong Zheng. "Weakly nonlinear and low frequency quantum transport in mesoscopic systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31239808.

Full text

APA, Harvard, Vancouver, ISO, and other styles

42

Zheng, Qingrong. "Weakly nonlinear and low frequency quantum transport in mesoscopic systems /." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B2026334X.

Full text

APA, Harvard, Vancouver, ISO, and other styles

43

Lu, Danyong. "Theoretical study of dynamic intensity fluctuations in mesoscopic 1D and Quasi-1D systems /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202009%20LU.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

Hemingway, Bryan J. "Magnetoconductance and Dynamic Phenomena in Single-Electron Transistors." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1352397253.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Cheung, Sai-Kit. "The study of weak localization effects on wave dynamics in mesoscopic media in the diffusive regime and at the localization transition /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202006%20CHEUNG.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Smith, Brice Christopher 1976. "Geometric and elastic properties and mechanical phase separation phenomena in self-assembling mesoscopic helical springs." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29610.

Full text

Abstract:

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2003. Includes bibliographical references (p. 279-300). Helical ribbons with pitch angles of either 11⁰ or 54⁰ self-assemble in a wide variety of quaternary surfactant-phospholipid/fatty acid-sterol-water systems. In all of the systems studied, the thermodynamically stable state for the sterol is plate like mono-hydrate crystals. However, the sterol is typically found to pass through a serious of metastable intermediates from filaments to helical ribbons to tubules before reaching the stable crystalline state. In the present work, we chose to focus on helical ribbons formed in the Chemically Defined Lipid Concentrate (CDLC) system. These helices typically have radii on the order of a few to a few tens of microns and lengths on the order of hundreds of microns. By tethering to these mesoscopic helical ribbons using Devcon 5-Minute Epoxy®, we have been able to elastically deform them, and thus examine their response to uniaxial tension. For small deformations, the low pitch helices behave like linear elastic springs with a spring constant for a typical example measured to be (4.80 +/- 0.77) x 10-6 N/m. From the observed spread in helix dimension, our theory predicts a corresponding range of spring constants for the structures of 10-7 to 10-4 N/m allowing, in principle, a great range of forces to be examined. Under larger tensions, both low and high pitch helices have been observed to reversibly separate into a straight domain with a pitch angle of 90Ê» and a helical domain with a pitch angle of (16.5 +/1 1.3)⁰ for the low pitch or (59.6 +/- 1.7)⁰ for the high pitch. Using a newly developed continuum elastic free energy model, we have shown that this phenomena can be understood as a mechanical phase transition of first order. (cont.) From this analysis, we have also been able to determine all of the parameters within our model, and to show that it is capable of self-consistently and quantitatively explaining all of the observed properties of these self-assembled helices. by Brice Christopher Smith. Ph.D.

APA, Harvard, Vancouver, ISO, and other styles

47

Wang, Baigeng. "General gauge invariant theory of transport in mesosopic systems /." Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20897558.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Falloon, Peter E. "Electron transport through domain walls in ferromagnetic nanowires." University of Western Australia. School of Physics, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0065.

Full text

Abstract:

[Truncated abstract] In this dissertation we present a theoretical study of electron transport through domain walls, with a particular focus on conductance properties, in order to understand various transport measurements that have been carried out recently on ferromagnetic nanowires. The starting point for our work is a ballistic treatment of transport through the domain wall. In this case conduction electrons are generally only weakly reflected by the domain wall, and the principal effect is a mixing of transmitted electron spins between up and down states. For small spin-splitting of conductance electrons the latter can be characterized by an appropriate adiabaticity parameter. We then incorporate the effect of spin-dependent scattering in the regions adjacent to the domain wall through a circuit model based on a generalization of the two-resistor theory of Valet and Fert. Within this model we find that the domain wall gives rise to an enhancement of resistance similar to the giant magnetoresistance effect found in ferromagnetic multilayer systems. The effect is largest in the limit of an abrupt wall, for which there is complete mistracking of spin, and decreases with increasing wall width due to the reduction of spin mistracking. For reasonable physical parameter values we find order-of-magnitude agreement with recent experiments. Going beyond the assumption of ballistic transport, we then consider the more realistic case of a domain wall subject to impurity scattering. A scattering matrix formalism is used to calculate conductance through a disordered region with either uniform magnetization or a domain wall. By combining either amplitudes or probabilities we are able to study both coherent and incoherent transport properties. The coherent case corresponds to elastic scattering by static defects, which is dominant at low temperatures, while the incoherent case provides a phenomenological description of the inelastic scattering present in real physical systems at room temperature. It is found that scattering from impurities increases the amount of spin mistracking of electrons travelling through a domain wall. This leads, in the incoherent case, to a reduction of conductance through the domain wall as compared to a uniformly magnetized region. In the coherent case, on the other hand, a reduction of weak localization and spin-reversing reflection amplitudes combine to give a positive contribution to domain wall conductance, which can lead to an overall enhancement of conductance due to the domain wall in the diffusive regime. A reduction of universal conductance fluctuations is found in a coherent disordered domain wall, which can be attributed to a decorrelation between spin-mixing and spin-conserving scattering amplitudes.

APA, Harvard, Vancouver, ISO, and other styles

49

Reguera, D. (David). "Mesoscopic Nonequilibrium Kinetics of Nucleation Processes." Doctoral thesis, Universitat de Barcelona, 2001. http://hdl.handle.net/10803/663185.

Full text

Abstract:

Esta tesis está dedicada al estudio de la cinética de la nucleación centrada en sus aspectos mesoscópicos y fuera equilibrio. Hemos desarrollado y presentado un marco teórico, basado en la Termodinámica Mesoscópica y de No Equilibrio (MNET), que garantiza una descripción flexible, bien fundamentada y conectada con las simulaciones de la dinámica de procesos fuera de equilibro, y en particular de la cinética de la nucleación. Este marco se ha mostrado especialmente útil para desvelar las sutilezas mesoscópicas y las influencias potenciales del carácter de no equilibrio del proceso. En particular, hemos analizado y resuelto algunos aspectos importantes y controvertidos en el ámbito de la nucleación, como son el Teorema de la Nucleación, donde hemos presentado una prueba termodinámica que ratifica su validez general; o la controversia que rodea a la incorporación de las contribuciones asociadas a los grados de libertad traslacionales y rotacionales, donde hemos incorporado por primera vez los efectos del movimiento y la rotación de los núcleos. También hemos analizado la influencia que puede tener la dinámica y las inhomogeneidades del medio en el proceso de nucleación. En particular, hemos estudiado detalladamente dos situaciones de interés práctico y experimental, como son la nucleación en presencia de gradientes térmicos, y en presencia de flujos cortantes, comparando las predicciones teóricas con los experimentos. Finalmente, también hemos señalado cómo se pueden incorporar estas influencias en las etapas avanzadas de la transición de fase, más allá de la etapa inicial de nucleación, lo cual permite una descripción más realista del proceso de cristalización.

APA, Harvard, Vancouver, ISO, and other styles

50

Wang, Xiaohua. "Characterization of Mesoscopic Fluid Films for Applications in SPM Imaging and Fabrication of Nanostructures on Responsive Materials." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/1068.

Full text

Abstract:

This dissertation focuses on characterization of the mesoscopic fluid film, testing its behavior in different application scenarios, including its role in near-field scanning probe microscopy imaging, contribution to the phononic mechanism in nanotribology phenomena, utilizing it as a natural environment in the study of carbohydrate-protein interactions, and harnessing it as bridge to transport ions in the fabrication of nanostructures on responsive polymer materials. Due to their high resolution and versatile applications in a variety of fields, the family of scanning probe microscopy (SPM) has found widespread acceptance as an analytical and fabrication tool. However, the working mechanism of SPM that allows maintaining the probe-sample distance constant is still controversial. At the heart the problem is a lack of precise knowledge about the nature of the probe-sample interaction. One key factor is the presence of a mesoscopic fluid-like layer that naturally forms at any surface at ambient condition in which most SPMs are operated. Its mesoscopic nature (~20 nm in thickness) results in extraordinary behavior compared to the properties of bulk liquid. For example, the effective shear viscosity of confined mesoscopic fluids is enhanced, and viscoelastic relaxation times are prolonged. Despite the wide use of SPM techniques in ambient air, the basis of their working mechanisms is still not well understood. The probe-sample interaction is monitored using a combination of tuning-fork based shear force microscopy and our recently developed near-field acoustic technique. To characterize the mesoscopic fluid film a series of experiments are performed under different conditions in order to explore the benefits of having extra probing (acoustic) technique in addition to the shear-force approach. The presence of mesoscopic fluid layers as a natural environment enables the detection of protein-carbohydrate interactions. We demonstrated the capability of our shear-force/acoustic technique to monitor the rupture of chemical bonds between carbohydrate and protein pairs. Finally, we present fabrication of nanostructures via electric-field assisted dip-pen nanolithography by exploiting the responsive feature of a particular class of polymers, where the mesoscopic fluid layer also plays an important role in pattern creation.

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Mesoscopic phenomena (Physics)'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles