Bulletin of the American Physical Society
2019 Joint Fall Meeting of the Texas Sections of APS, AAPT and Zone 13 of the SPS
Volume 64, Number 18
Friday–Saturday, October 25–26, 2019; Lubbock, Texas
Session B02: Condensed Matter, Nanoscience and Computational Physics I |
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Chair: Myounghwan Kim, Texas Tech University Room: Student Union Building Canyon Room |
Friday, October 25, 2019 10:21AM - 10:33AM |
B02.00001: Solving the Relativistic Two-Coulomb-Center Problem using Monte Carlo Methods S.A. Alexander, R.L. Coldwell Using Variational Monte Carlo methods we have computed highly accurate trial wavefunction forms for the ground states of H$+$ and Th179$+$. These trial wavefunctions satisfy the 4-component Dirac Equation and can be used to calculate a variety of interesting expectation values. We will compare our results with those in the literature. [Preview Abstract] |
Friday, October 25, 2019 10:33AM - 10:45AM |
B02.00002: Seafloor topography estimation from Vertical Gravity Gradients using Particle Swarm Optimization Yelbir Kazhykarim, Soumya D. Mohanty The Earth's Vertical Gravity Gradient (VGG) can be used to map seafloor topography but presents a challenging inverse problem. A promising approach is forward modeling, in which one searches over a set of candidate topographies and selects the one whose predicted VGG best fits the observed one. The main bottleneck here is solving the associated high-dimensional and non-linear optimization problem. Yang et al (2018) demonstrated a method in which the topography is parametrized by heights of mass elements on a rectangular grid and the $\approx 10^4$ dimensional optimization problem is tackled with simulated annealing (SA). We propose a computationally much cheaper method, using a stochastic optimization method known as Particle Swarm Optimization (PSO) and representing the topography as a linear combination of Radial Basis Functions (RBFs). First results, obtained without any tuning, show that the MATLAB code achieves an RMS error of 700 m with 500 RBFs (1500 parameters) and a 30 min run time. This is comparable to the error of 350 m from the much more expensive SA method that takes hours. Improvements to our method are likely to result in state of the art performance levels. [Preview Abstract] |
Friday, October 25, 2019 10:45AM - 10:57AM |
B02.00003: Induced superconducting state in multilayer WTe$_{\mathrm{2}}$ by proximity effect Xurui Zhang, Xiaoyan Shi Superconductivity in topological materials has attracted a great deal of interest as an effective way to realize Majorana modes in condensed matter physics. It has been predicted that the proximity effect between an s-wave superconductor and the surface states of a strong topological insulator (TI) could result in a two-dimensional (2D) state which supports Majorana bound states. We fabricated superconductor (Ta)-WTe$_{\mathrm{2}}$-superconductor (Ta) junction devices based on WTe$_{\mathrm{2}}$ with two different thickness. Here we report the observations of the proximity effect induced superconducting states revealed by magnetoresistance (MR) and I-V measurements in both devices. ~Distinct zero-bias conductance peaks in differential conductance measurements, might be as a sign of Majorana state, were also observed. In addition, the multi-peaks of differential resistance at low temperature and magnetic field marks an interesting superconducting gap structure. [Preview Abstract] |
Friday, October 25, 2019 10:57AM - 11:09AM |
B02.00004: Ultrafast dynamical processes in low dimensional materials Ioannis Chatzakis Low-dimensional (e.g. atomically thin) materials continue to gain prominence in applications ranging from electronics to photonics and alternative energy generation systems. Critical to efficiently developing these systems is the understanding of the fundamental processes related to the dynamics of charge carriers, phonons, and other excitations (i.e. excitons, polaritons). In this talk, I will focus on electron-phonon interactions in carbonic materials through which electrons lose their energy and become thermally equilibrated, and the phonon-phonon scattering processes responsible for energy release into the environment as heat. I will also discuss a representative example of the recombination mechanism of the photo-generated charge carriers in a two-dimensional sheet of hexagonal boron nitride.. [Preview Abstract] |
Friday, October 25, 2019 11:09AM - 11:21AM |
B02.00005: Photoinduced Heating Enhancement of Metallic Glass Nanowires Ceren Uzun, Chandra Sekhar Meduri, Niloofar Kahler, Luis Grave de Peralta, Jena M. McCollum, Michelle Pantoya, Golden Kumar, Ayrton A. Bernussi Materials with high photo-thermal efficiency are essential in a wide variety of applications from medicine to renewable energy. Photo-thermal materials effectively absorb and convert light into heat. Nanostructures have proven to enhance absorption and heat retention owing to their large surface areas and restricted heat pathways. Here, we demonstrate that the optical absorption and heat conversion in near-infrared can be enhanced by using metallic glass nanowires whose geometry can be readily tailored through thermoplastic molding. Infrared thermography measurements and heat transport simulations reveal that the photo-induced temperature rise can be amplified by increasing the length of nanowires and decreasing the thickness of the supporting substrate. Temperature above 500\textdegree C can be rapidly achieved to induce a controlled phase transformation from amorphous to crystalline state in metallic glass nanowires while maintaining their geometrical integrity. Photo-induced temperature rise can be used in optical ignition applications as demonstrated by an example of thermite powder. [Preview Abstract] |
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