Browsing Faculty Research by Title
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Myers, KD; Canfield, PC; Kalatsky, VA; Pokrovsky, Valery L. (American Physical Society, 1999)[more][less]
Abstract: Measurements
of the magnetization of DyAgSb2 reveal a complex system of up to 11 well-defined metamagnetic states for the field applied within the basal plane. Measurements of the magnetization vs the angle the applied field makes with respect to the [110] axis show the Dy3+ moments are constrained to lie along one of the four [110] directions within the basal plane. From the angular dependence of the critical fields and plateau magnetizations, the net distribution of the moments may be deduced for each state. Finally, the coupling constants are calculated within the framework of the "four-position clock model." [S0163-1829(99)04302-7].
Description: Journals published by the American Physical Society can be found at http://journals.aps.org/
URI: http://dx.doi.org/10.1103/PhysRevB.59.1121 Files in this item: 1
PhysRevB.59.1121.pdf (209.9Kb) -
Canfield, PC; Budko, SL; Cho, BK; Lacerda, A.; Farrell, D.; JohnstonHalperin, E.; Kalatsky, VA; Pokrovsky, Valery L. (American Physical Society, 1997)[more][less]
Abstract: Detailed measurements of M(2 K, H, theta) of HoNi2B2C, where theta is the angle that the applied field H makes with the [110] axis while remaining perpendicular to the crystallographic c axis, reveal three metamagnetic transitions with angular dependences H-c1 = (4.1 +/- 0.1 kG)/cos(theta), H-c2 = 8.4 +/- 0.2 kG/cos(phi), and H-c3 = (6.6 +/- 0.2 kG)/sin(phi), where phi = theta-45 is the angle from the [100] axis. The high-field saturated moment, M(sat) approximate to 10 mu(B)cos theta is consistent with the local moments being confined to the [110] direction. The locally saturated moments for fields between H-ci (i = 1, 2, 3) also manifest angular dependences that are consistent with combinations of local moments along [110] axes. Analysis of these data lead us to infer that the net distribution of moments is (up arrow down arrow up arrow down arrow up arrow down arrow) for H up arrow up arrow-->) for H-c2 up arrow up arrow-->) for H-c2 H-c3.
Description: Journals published by the American Physical Society can be found at http://journals.aps.org/
URI: http://dx.doi.org/10.1103/PhysRevB.55.970 Files in this item: 1
PhysRevB.55.970.pdf (196.3Kb) -
Pokrovsky, Valery L.; Lyuksyutov, Igor F.; NATTERMANN, T. (American Physical Society, 1992)[more][less]
Description: Journals published by the American Physical Society can be found at http://journals.aps.org/
URI: http://dx.doi.org/10.1103/PhysRevB.46.3071 Files in this item: 0
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Chen, LW; Ko, Che Ming. (American Physical Society, 2006)[more][less]
Abstract: The anisotropic flow of charged hadrons in asymmetric Cu+Au collisions at the Relativistic Heavy Ion Collider is studied in a multiphase transport model. Compared with previous results for symmetric Au+Au collisions, charged hadrons produced around midrapidity in asymmetric collisions are found to have a stronger directed flow v(1) and their elliptic flow v(2) is also more sensitive to the parton scattering cross section. Although higher order flows v(3) and v(4) are small at all rapidities, both v(1) and v(2) in these collisions are appreciable and show an asymmetry in forward and backward rapidities.
Description: Journals published by the American Physical Society can be found at http://publish.aps.org/
URI: http://dx.doi.org/10.1103/PhysRevC.73.014906 Files in this item: 1
PhysRevC.73.014906.pdf (403.9Kb) -
Rathnayaka, KDD; Naugle, Donald G.; Cho, BK; Canfield, PC. (American Physical Society, 1996)[more][less]
Abstract: The in-plane resistivity and magnetization measurements as a function of the magnitude and direction of the magnetic field and the temperature are reported for single-crystal samples of the HoNi2B2C magnetic superconductor. Features corresponding to several distinct magnetic phases and the coexistence of superconductivity with two of the magnetic phases are observed. Contrary to previous measurements for polycrystalline samples, reentrant superconductivity is not observed in the absence of a field for these samples. The measurements indicate an extremely rich interplay between superconductivity and different magnetic structures that can be influenced by field, temperature, and current. The results correlate quantitatively with and complement previous determinations of the magnetic phase diagram and qualitatively with determinations of the superconducting phases by measurements of the single-crystal magnetization and heat capacity. HoNi2B2C is highly anisotropic, and phase diagrams for the field along the (100) and (001) directions are presented.
Description: Journals published by the American Physical Society can be found at http://journals.aps.org/
URI: http://dx.doi.org/10.1103/PhysRevB.53.5688 Files in this item: 1
PhysRevB.53.5688.pdf (196.1Kb) -
Kayali, MA; Pokrovsky, Valery L. (American Physical Society, 2004)[more][less]
Abstract: We study the transport properties of vortex matter in a superconducting thin film separated by a thin insulator layer from a ferromagnetic layer. We assume an alternating stripe structure for both FM and superconducting (SC) layers as found in S. Erdin [Phys. Rev. Lett. 88, 017001 (2002)]. We calculate the periodic pinning force in the stripe structure resulting from a highly inhomogeneous distribution of the vortices and antivortices. We show that the transport in SC-FM bilayer is highly anisotropic. In the absence of random pinning it displays a finite resistance for the current perpendicular to stripe and is superconducting for the current parallel to stripes. The average vortex velocity, electric field due to the vortex motion, Josephson frequency, and higher harmonics of the vortex oscillatory motion are calculated.
Description: Journals published by the American Physical Society can be found at http://journals.aps.org/
URI: http://dx.doi.org/10.1103/PhysRevB.69.132501 Files in this item: 1
PhysRevB.69.132501.pdf (57.56Kb) -
Sinitsyn, N. A.; MacDonald, A. H.; Jungwirth, T.; Dugaev, V. K.; Sinova, Jairo. (American Physical Society, 2007)[more][less]
Abstract: The anomalous Hall effect (AHE) is a consequence of spin-orbit coupling in a ferromagnetic metal and related primarily to density-matrix response to an electric field that is off-diagonal in band index. For this reason disorder contributions to the AHE are difficult to treat systematically using a semiclassical Boltzmann equation approach, even when weak localization corrections are disregarded. In this article we explicitly demonstrate the equivalence of an appropriately modified semiclassical transport theory which includes anomalous velocity and side-jump contributions and microscopic Kubo-Streda perturbation theory, with particular unconventional contributions in the semiclassical theory identified with particular Feynman diagrams when calculations are carried out in a band-eigenstate representation. The equivalence we establish is verified by explicit calculations for the case of the two-dimensional Dirac model Hamiltonian relevant to graphene.
Description: Journals published by the American Physical Society can be found at http://journals.aps.org/
URI: http://dx.doi.org/10.1103/PhysRevB.75.045315 Files in this item: 1
PhysRevB.75.045315.pdf (628.3Kb) -
Nunner, Tamara S.; Sinitsyn, N. A.; Borunda, Mario F.; Dugaev, V. K.; Kovalev, A. A.; Abanov, Artem; Timm, Carsten; Jungwirth, T.; Inoue, Jun-ichiro; MacDonald, A. H.; Sinova, Jairo. (American Physical Society, 2007)[more][less]
Abstract: The anomalous Hall effect in a magnetic two-dimensional electron gas with Rashba spin-orbit coupling is studied within the Kubo-Streda formalism in the presence of pointlike potential impurities. We find that all contributions to the anomalous Hall conductivity vanish to leading order in disorder strength when both chiral subbands are occupied. In the situation that only the majority subband is occupied, all terms are finite in the weak scattering limit and the total anomalous Hall conductivity is dominated by skew scattering. We compare our results to previous treatments and resolve some of the discrepancies present in the literature.
Description: Journals published by the American Physical Society can be found at http://journals.aps.org/
URI: http://dx.doi.org/10.1103/PhysRevB.76.235312 Files in this item: 1
PhysRevB.76.235312.pdf (441.6Kb) -
Fitzsimmons, M. R.; Lederman, D.; Cheon, M.; Shi, H.; Olamit, J.; Roshchin, Igor V.; Schuller, Ivan K. (American Physical Society, 2008)[more][less]
Abstract: Using neutron diffraction, we measured the sizes of antiferromagnetic domains in three ferromagnet/antiferromagnet bilayer samples as a function of the magnitude and sign of exchange bias, temperature, and antiferromagnet composition. Neutron-scattering techniques were applied to thin films with masses less than 10 mu g. We found the antiferromagnetic domain size to be consistently small regardless of the exchange bias. For a Co/untwinned single crystalline antiferromagnet (AF)-fluoride bilayer, the antiferromagnetic domain size is comparable to the crystallographic domain size of the AF. For one sample the highest temperature at which the exchange bias was nonzero (i.e., the blocking temperature) was suppressed by similar to 3 K compared to the Neel temperature of the antiferromagnet.
Description: Journals published by the American Physical Society can be found at http://journals.aps.org/
URI: http://dx.doi.org/10.1103/PhysRevB.77.224406 Files in this item: 1
PhysRevB.77.224406.pdf (980.3Kb) -
Pal, S.; Ko, Che Ming; Lin, ZW; Zhang, B. (American Physical Society, 2000)[more][less]
Abstract: We compare relativistic transport model calculations to recent data on the sideward flow of neutral strange K-s(0) mesons for Au+Au collisions at 6A GeV. A soft nuclear equation of state is found to describe very well the positive proton flow data measured in the same experiment. In the absence of the kaon potential, the K-0 flow pattern is similar to that of protons. The kaon flow becomes negative if a repulsive kaon potential determined from the impulse approximation is introduced. However, this potential underestimates the data which exhibit larger antiflow. An excellent agreement with the data is obtained when a relativistic scalar-vector kaon potential, that has stronger density dependence, is used. We further find that the transverse momentum dependence of directed and elliptic flow is quite sensitive to the kaon potential in dense matter.
Description: Journals published by the American Physical Society can be found at http://publish.aps.org/
URI: http://dx.doi.org/10.1103/PhysRevC.62.061903 Files in this item: 1
PhysRevC.62.061903.pdf (78.03Kb) -
Li, GQ; Ko, Che Ming. (American Physical Society, 1996)[more][less]
Abstract: We study antikaon flow in heavy-ion collisions at SIS energies based on the relativistic transport model (RVUU 1.0). The production of antikaons from both baryon-baryon and pion-baryon collisions are included. Taking into account only elastic and inelastic collisions of the antikaon with nucleons and neglecting its mean-field potential as in the cascade model, a strong antiflow or anticorrelation of antikaons with respect to nucleons is seen as a result of the strong absorption of antikaons by nucleons. However, the antiflow of antikaons disappears after including also their propagation in the attractive mean-field potential. The experimental measurement of antikaon flow in heavy-ion collision will be very useful in shedding light on the relative importance of antikaon absorption versus its mean-field potential.
Description: Journals published by the American Physical Society can be found at http://publish.aps.org/
URI: http://dx.doi.org/10.1103/PhysRevC.54.R2159 Files in this item: 1
PhysRevC.54.R2159.pdf (95.63Kb) -
Ko, Che Ming; Asakawa, M.; Levai, P. (American Physical Society, 1992)[more][less]
Abstract: In the Walecka model, the antilambda mass in dense nuclear matter is smaller than its value in free space. This reduces the threshold for antilambda production in dense matter that forms in the compression stage of ultrarelativistic heavy ion collisions. Because of the large number of mesons produced in the collision, the process KM --> LAMBDA-BAR N, where M denotes either a pion or a rho meson, is shown to be important and provides thus a plausible explanation for the observed enhancement of antilambda yield in recent experiments carried out at CERN SPS with nuclear beams.
Description: Journals published by the American Physical Society can be found at http://publish.aps.org/
URI: http://dx.doi.org/10.1103/PhysRevC.46.1072 Files in this item: 1
PhysRevC.46.1072.pdf (246.9Kb) -
LI, GQ; Ko, Che Ming. (American Physical Society, 1994)[more][less]
Abstract: Antiproton production in Ni+Ni collisions at 1.85 GeV/nucleon is studied in the relativistic Vlasov-Uehling-Uhlenbeck model. The self-energies of the antiproton are determined from the nucleon self-energies by the G-parity transformation. Also, the final-state interactions of the antiproton including both rescattering and annihilation are explicitly treated. With a soft nuclear equation of state, the calculated antiproton momentum spectrum is in good agreement with recent experimental data from the heavy-ion synchrotron at Gesellschaft, fur Schwerionenforschung Darmstadt. The effect due to the reduced nucleon and antinucleon masses in a medium is found to be more appreciable than in earlier Bevalac experiments with lighter systems and at higher energies.
Description: Journals published by the American Physical Society can be found at http://publish.aps.org/
URI: http://dx.doi.org/10.1103/PhysRevC.50.1725 Files in this item: 1
PhysRevC.50.1725.pdf (252.9Kb) -
Chemakin, I.; Cianciolo, V.; Cole, BA; Fernow, R.; Frawley, A.; Gilkes, M.; Gushue, S.; Hartouni, E.; Hiejima, H.; Justice, M.; Kang, JH; Keane, D.; Kirk, H.; Kreisler, M.; Maeda, N.; McGrath, R. L.; Mioduszewski, Saskia; Morrison, D.; Moulson, M.; Namboodiri, N.; Rai, G.; Read, K.; Remsberg, L.; Rosati, M.; Shin, Y.; Soltz, R.; Sorensen, S.; Thomas, J.; Torun, Y.; Winter, D.; Yang, X.; Zajc, WA; Zhang, Y. (American Physical Society, 2001)[more][less]
Description: Journals published by the American Physical Society can be found at http://publish.aps.org/
URI: http://dx.doi.org/10.1103/PhysRevC.64.064908 Files in this item: 0
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Bales, Stephen (October 12, 2009)[more][less]
Abstract: This historical study examines the Aristotelian foundations of the Library and Museum of Alexandria for the purpose of (1) understanding how the Library and Museum differed from preceding ancient Near Eastern information institutions (i.e., “protolibraries”) and (2) how Aristotle’s methodologies for producing scientific knowledge were carried out in Alexandria. While protolibraries served as safeguards for maintaining a static cultural/political “stream of tradition” and created, organized, and maintained “library” documents to this end, the Library of Alexandria was a tool for theoretical knowledge creation. The Library materialized Aristotelian pre-scientific theory, specifically dialectic and served the scholarly community of the Museum in its research. Following the Library, collections of materialized endoxa, or recorded esteemed opinions, became a necessary tool for use by scholarly communities. The Library established the post-Aristotelian paradigm under which academic libraries still operate. Although the Library of Alexandria represented a fundamental shift in the meaning and purpose of collections of recorded documents, a feminist critique of the post-Aristotelian library shows that the academic library, while used in knowledge creation, is rooted in a foundationalist philosophy that validates and maintains the status quo.
Description: This is the corrected version of the doctoral dissertation (as of Oct 9, 2009): Bales, Stephen. “Aristotle’s Contribution to Scholarly Communication.” PhD diss., University of Tennessee, 2008. Corrections were made to remedy minor errors as well as substantive errors and citation errors. A list of corrections appears at the end of this document. The original, uncorrected version is catalogued at the University of Tennessee, Knoxville and by OCLC (#444510431).
URI: http://hdl.handle.net/1969.1/88061 Files in this item: 1
Balesdissertation2008_corrected.pdf (1.625Mb) -
Mukhamedzhanov, AM; Schmitt, R. P.; Tribble, Robert E.; Sattarov, A. (American Physical Society, 1995)[more][less]
Abstract: We consider the radiative capture process alpha+d-->Li-6+gamma at energies, E(c.m.)less than or equal to 300 keV, that are relevant for astrophysical processes. Due to the peripheral character of the reaction, the overall normalization of the astrophysical factor S-24 is entirely governed by one quantity, the asymptotic normalization coefficient C-01 for Li-6-->alpha+d. Using the recently well established value for this constant C-01=2.3+/-0.12 fm(-1/2), we calculated S-24 taking into account both E1 and E2 contributions. Our recommended value for S-24 is 2.57 MeV nb at the most effective energy for the capture reaction in astrophysical processes, E(c.m.)=70 keV, which gives a reaction rate 0.036 cm(3) mole(-1) s(-1) at the temperature 0.8x10(9) K. We found a significant energy dependence of S-24 at astrophysical energies. At energies of less than 110 keV, the E1 component dominates over the E2 component. AtE(c.m.)=70 keV, the E1 contribution to the total transition is about 58%.
Description: Journals published by the American Physical Society can be found at http://publish.aps.org/
URI: http://dx.doi.org/10.1103/PhysRevC.52.3483 Files in this item: 1
PhysRevC.52.3483.pdf (222.0Kb) -
La Cognata, M.; Romano, S.; Spitaleri, C.; Cherubini, S.; Crucilla, V.; Gulino, M.; Lamia, L.; Pizzone, R. G.; Tumino, A.; Tribble, Robert E.; Fu, Changbo; Goldberg, V. Z.; Mukhamedzhanov, A. M.; Schmidt, D.; Tabacaru, G.; Trache, L.; Irgaziev, B. F. (American Physical Society, 2007)[more][less]
Abstract: The low-energy bare-nucleus cross section for (15)N(p, alpha)(12)C is extracted by means of the Trojan horse method applied to the (2)H((15)N,alpha(12)C)n reaction at E(beam) = 60 MeV. For the first time we applied the modified half-off-energy-shell resonant R-matrix method that takes into account off-energy-shell effects and initial- and final-state interactions. In particular it has been shown that inclusion of Coulomb (15)N-d scattering and off-shell effects do not affect the determination of the astrophysical factor. Also the simple plane-wave approximation used in previous analyses is justified. The results extracted via the Trojan horse method are compared to direct data in the same energy region and show very good agreement in the energy interval 70-312 keV. These results confirm the extrapolations of the S factor reported in literature.
Description: Journals published by the American Physical Society can be found at http://publish.aps.org/
URI: http://dx.doi.org/10.1103/PhysRevC.76.065804 Files in this item: 1
PhysRevC.76.065804.pdf (894.6Kb) -
Sattarov, A.; Mukhamedzhanov, AM; Azhari, A.; Gagliardi, Carl A.; Trache, L.; Tribble, Robert E. (American Physical Society, 1999)[more][less]
Abstract: The Be-9(p, gamma) B-10 reaction plays an important role in primordial and stellar nucleosynthesis of light elements in the p shell, but the energy dependence of S(E) has not been well understood. We reanalyze the existing Be-9(p, gamma) B-10 experimental data within the framework of the R-matrix method. The direct capture part of the S factor is calculated using the experimentally measured asymptotic normalization coefficients for B-10 --> Be-9 + p. The fitted parameters of the low-lying B-10 resonances are also required to be consistent with previous measurements of Li-6(alpha, gamma) log. A good simultaneous fit to both radiative capture reactions is found, in contrast to previous analyses. These results demonstrate that experimentally measured asymptotic normalization coefficients, coupled to the R-matrix method, can provide a reasonable determination of direct radiative capture rates, even when the captured proton is tightly bound in the final nucleus. [S0556-2813(99)03608-0].
Description: Journals published by the American Physical Society can be found at http://publish.aps.org/
URI: http://dx.doi.org/10.1103/PhysRevC.60.035801 Files in this item: 1
PhysRevC.60.035801.pdf (75.79Kb) -
Mukhamedzhanov, AM; Azhari, A.; Burjan, V.; Gagliardi, Carl A.; Kroha, V.; Sattarov, A.; Tang, X.; Trache, L.; Tribble, Robert E. (American Physical Society, 2002)[more][less]
Abstract: We reanalyze the C-13(p,gamma)N-14 radiative capture reaction within the R-matrix approach. The low-energy astrophysical S factor has important contributions from both resonant and onresonant captures. The normalization of the nonresonant component of the transition to a particular N-14 bound state is expressed in terms of the asymptotic normalization coefficient (ANC). In the analysis we use the experimental ANC's inferred from the C-13(N-14,C-13)N-14 and C-13(He-3,d)N-14 reactions. The fits of the calculated S factors to the experimental data are sensitive to the ANC values and are used to test the extracted ANC's. We find that for transitions to all the states in N-14, except the third excited state, the ANC's determined from the transfer reactions provide the best fit. The astrophysical factor we obtain, S(0)=7.7+/-1.1 keV b, is in excellent agreement with previous results.
Description: Journals published by the American Physical Society can be found at http://publish.aps.org/
URI: http://dx.doi.org/10.1103/PhysRevC.66.027602 Files in this item: 1
PhysRevC.66.027602.pdf (58.24Kb) -
Banu, A.; Al-Abdullah, T.; Fu, C.; Gagliardi, Carl A.; McCleskey, M.; Mukhamedzhanov, A. M.; Tabacaru, G.; Trache, L.; Tribble, Robert E.; Zhai, Y.; Carstoiu, F.; Burjan, V.; Kroha, V. (American Physical Society, 2009)[more][less]
Abstract: The cross section of the radiative proton capture reaction on the drip line nucleus (12)N was investigated using the asymptotic normalization coefficient (ANC) method. We have used the (14)N((12)N,(13)O)(13)C proton transfer reaction at 12 MeV/nucleon to extract the ANC for (13)O ->(12)N+p and calculate from it the direct component of the astrophysical S factor of the (12)N(p,gamma)(13)O reaction. The optical potentials used and the distorted-wave Born approximation analysis of the proton transfer reaction are discussed. For the entrance channel, the optical potential was inferred from an elastic scattering measurement carried out at the same time as the transfer measurement. From the transfer, we determined the square of the ANC, C(p1/2)(2)((13)O(g.s.))=2.53 +/- 0.30 fm(-1), and hence a value of 0.33(4) keV b was obtained for the direct astrophysical S factor at zero energy. Constructive interference at low energies between the direct and resonant captures leads to an enhancement of S(total)(0)=0.42(6) keV b. The (12)N(p,gamma)(13)O reaction was investigated in relation to the evolution of hydrogen-rich massive Population III stars, for the role that it may play in the hot pp-chain nuclear burning processes, possibly occurring in such objects.
Description: Journals published by the American Physical Society can be found at http://publish.aps.org/
URI: http://dx.doi.org/10.1103/PhysRevC.79.025805 Files in this item: 1
PhysRevC.79.025805.pdf (500.7Kb)
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