Publications - Physics
http://hdl.handle.net/10027/160
2018-12-16T22:21:02Z
2018-12-16T22:21:02Z
Relaxation Times for Chiral Transport Phenomena and Spin Polarization in Strongly Coupled Plasma
Li, Shiyong
Yee, Ho-Ung
http://hdl.handle.net/10027/22829
2018-11-08T09:01:09Z
2018-09-01T00:00:00Z
Relaxation Times for Chiral Transport Phenomena and Spin Polarization in Strongly Coupled Plasma
Li, Shiyong; Yee, Ho-Ung
We compute the dynamical relaxation times for chiral transport phenomena in a strongly coupled regime using the AdS/CFT correspondence. These relaxation times can be a useful proxy for the dynamical timescale for achieving equilibrium spin polarization of quasiparticles in the presence of a magnetic field and fluid vorticity. We identify the Kubo relations for these relaxation times and clarify some previous issues regarding time dependence of the chiral vortical effect. We study the consequences of imposing time-reversal invariance on parity-odd thermal noise fluctuations that are related to chiral transport coefficients by the fluctuation-dissipation relation. We find that time-reversal invariance dictates the equality between some of the chiral transport coefficients as well as their relaxation times.
Copyright @ American Physical Society
2018-09-01T00:00:00Z
Benchmarking the GW Approximation and Bethe–Salpeter Equation for Groups IB and IIB Atoms and Monoxides
Hung, Linda
Bruneval, Fabien
Baishya, Kopinjol
Ogut, Serder
http://hdl.handle.net/10027/22273
2018-06-19T08:01:02Z
2017-04-07T00:00:00Z
Benchmarking the GW Approximation and Bethe–Salpeter Equation for Groups IB and IIB Atoms and Monoxides
Hung, Linda; Bruneval, Fabien; Baishya, Kopinjol; Ogut, Serder
Energies from the GW approximation and the Bethe–Salpeter equation (BSE) are benchmarked against the excitation energies of transition-metal (Cu, Zn, Ag, and Cd) single atoms and monoxide anions. We demonstrate that best estimates of GW quasiparticle energies at the complete basis set limit should be obtained via extrapolation or closure relations, while numerically converged GW-BSE eigenvalues can be obtained on a finite basis set. Calculations using real-space wave functions and pseudopotentials are shown to give best-estimate GW energies that agree (up to the extrapolation error) with calculations using all-electron Gaussian basis sets. We benchmark the effects of a vertex approximation (ΓLDA) and the mean-field starting point in GW and the BSE, performing computations using a real-space, transition-space basis and scalar-relativistic pseudopotentials. While no variant of GW improves on perturbative G0W0 at predicting ionization energies, G0W0ΓLDA-BSE computations give excellent agreement with experimental absorption spectra as long as off-diagonal self-energy terms are included. We also present G0W0 quasiparticle energies for the CuO–, ZnO–, AgO–, and CdO– anions, in comparison to available anion photoelectron spectra.
Copyright @ American Chemical Society
2017-04-07T00:00:00Z
Vortex cutting in superconductors.
Glatz A
Vlasko-Vlasov VK
Kwok WK
Crabtree GW
http://hdl.handle.net/10027/21415
2018-04-18T09:59:38Z
2016-08-09T00:00:00Z
Vortex cutting in superconductors.
Glatz A; Vlasko-Vlasov VK; Kwok WK; Crabtree GW
Vortex cutting and reconnection is an intriguing and still-unsolved problem central to many areas of classical
and quantum physics, including hydrodynamics, astrophysics, and superconductivity. Here, we describe a
comprehensive investigation of the crossing of magnetic vortices in superconductors using time dependent
Ginsburg-Landau modeling. Within a macroscopic volume, we simulate initial magnetization of an anisotropic
high temperature superconductor followed by subsequent remagnetization with perpendicular magnetic fields,
creating the crossing of the initial and newly generated vortices. The time resolved evolution of vortex lines as they
approach each other, contort, locally conjoin, and detach, elucidates the fine details of the vortex-crossing scenario
under practical situations with many interacting vortices in the presence of weak pinning. Our simulations also
reveal left-handed helical vortex instabilities that accompany the remagnetization process and participate in the
vortex crossing events.
This is a non-final version of an article published in final form in Glatz, A., Vlasko-Vlasov, V. K., Kwok, W. K. and Crabtree, G. W. Vortex cutting in superconductors. Physical Review B. 2016. 94(6). DOI: 10.1103/PhysRevB.94.064505.
2016-08-09T00:00:00Z
Origin of the turn-on temperature behavior in WTe2
Wang, Y. L.
Thoutam, L. R.
Xiao, Z. L.
Hu, J.
Das, S.
Mao, Z. Q.
Wei, J.
Divan, R.
Luican-Mayer, A.
Crabtree, G. W.
Kwok, W. K.
http://hdl.handle.net/10027/21137
2018-04-18T09:52:24Z
2015-11-03T00:00:00Z
Origin of the turn-on temperature behavior in WTe2
Wang, Y. L.; Thoutam, L. R.; Xiao, Z. L.; Hu, J.; Das, S.; Mao, Z. Q.; Wei, J.; Divan, R.; Luican-Mayer, A.; Crabtree, G. W.; Kwok, W. K.
A hallmark of materials with extremely large magnetoresistance (XMR) is the transformative turn-on temperature behavior: when the applied magnetic field H is above certain value, the resistivity versus temperature ρ(T) curve shows a minimum at a field dependent temperature T∗, which has been interpreted as a magnetic-field-driven metal-insulator transition or attributed to an electronic structure change. Here, we demonstrate that ρ(T) curves with turn-on behavior in the newly discovered XMR material WTe2 can be scaled as MR∼(H/ρ0)m with m≈2 and ρ0 being the resistivity at zero field. We obtained experimentally and also derived from the observed scaling the magnetic field dependence of the turn-on temperature T∗∼(H-Hc)ν with ν≈1/2, which was earlier used as evidence for a predicted metal-insulator transition. The scaling also leads to a simple quantitative expression for the resistivity ρ∗≈2ρ0 at the onset of the XMR behavior, which fits the data remarkably well. These results exclude the possible existence of a magnetic-field-driven metal-insulator transition or significant contribution of an electronic structure change to the low-temperature XMR in WTe2. This work resolves the origin of the turn-on behavior observed in several XMR materials and also provides a general route for a quantitative understanding of the temperature dependence of MR in both XMR and non-XMR materials.
This is a copy of an article published in the Physical Review B. © 2015 American Physical Society. http://link.aps.org/doi/10.1103/PhysRevB.92.180402
2015-11-03T00:00:00Z