Condensed Matter Physics Commons^™

Direct Observation Of Ferroelectric Switching In Two-Dimensional Mos2, A. Lipatov, P. Chaudhary, Z. Guan, H. Lu, G. Li, O. Crégut, K. D. Dorkenoo, R. Proksch, Ding-Fu Shao, Evgeny Y. Tsymbal, J. Íñiguez, A. Sinitskii, Alexei Gruverman

Evgeny Tsymbal Publications

No abstract provided.

Periodic Trends In The Infrared And Optical Absorption Spectra Of Metal Chalcogenide Clusters, Alain Ward

Theses and Dissertations

We have investigated the Optical absorption, Infrared spectra, Binding Energies, and various other cluster properties to determine the existence of periodic trend for Transition Metal Chalcogenide Clusters ligated with CO ligands. We were motivated to answer the question of whether periodic behavior can be observed in properties of octahedral metal-chalcogenide clusters. We have used the Amsterdam Density Functional code to calculate the electronic structure of Transition Metal Chalcogenide Clusters using gradient-corrected density functional theory. We determined the existence of several periodic trends in properties of octahedral Transition Metal Chalcogenide Clusters TM₆Se₈(CO)₆. To investigate these …

Magnetic Charge Ordering Of Pinwheel Artificial Spin Ice In In-Plane External Magnetic Fields And Its Application For Tunable Vortex Pinning, Timothy Draher

Graduate Research Theses & Dissertations

Pinwheel artificial spin ice (ASI) systems fabricated using permalloy nanobars offer tunable control of superconducting vortices in an ASI-superconductor hybrid. Vortex pinningis achieved by tuning the ordering of the ASI’s magnetic charge distribution via an external field to create an optimal potential energy landscape to which superconducting vortex motion can be impeded or pinned. Magnetic charge ordering in a pinwheel ASI is visualized using MuMax3 micromagnetic simulations to aid in characterizing the correlation of charge ordering amongst the spin ice system with the application of the external field. Vortex pinning is characterized in a sample of pinwheel spin ice patterned …

Understanding The Degradation Mechanism In Methyl Ammonium Lead Halide Perovskite And Black Phosphorene Via Electrical Transport Study, Huda Saleh Aljeailan

Theses and Dissertations--Physics and Astronomy

This work seeks to understand the degradation mechanism of technically important material systems such as black phosphorene (BP), arsenic phosphorene (AsP) and Methyl ammonium lead iodide (CH₃NH₃PbI₃) perovskite. Degradation studies were conducted by studying the in-situ electrical transport properties (resistance and thermoelectric power (TEP)) of these materials in vacuum (under annealed condition) and after exposure to the ambient air.

BP and both exhibited p-type semiconducting (positive TEP) behavior under annealed conditions and the changes in their transport properties upon exposure to ambient air can be explained as due to the charge transfer between the …

Magnetization Dynamics In A Modified Square Artificial Spin Ice, Amrit Kaphle

Theses and Dissertations--Physics and Astronomy

Artificial spin ices are magnetic metamaterials consisting of nanomagnet arrays in a 2-D lattice. Typically, these nanomagnet arrays are binary macrospins that can only be in an up or down state similar to the Ising spins. They have been intensively used to study magnetic frustration and ordering phenomena in a controlled environment. The hexagonal artificial spin ice and square artificial spin ice are among the most heavily studied systems. In this dissertation, we designed a modified square artificial spin ice system by an ordered substitution of a double-segment for a nanomagnet array in the unit cell of square artificial spin …

Thermalization And Quantum Information In Conformal Field Theory, Ashish Kakkar

Theses and Dissertations--Physics and Astronomy

The consequences of the constraints of conformal symmetry are far-reaching within
theoretical physics. In this dissertation we address a series of questions in conformal
field theory: 1) We calculate the spectrum of qKdV charges in a large central charge
expansion. 2) We determine the corrections to bulk information geometry from 1/N
contributions to holographic correlators. 3) We study the higher genus partitions
functions of CFTs associated with classical and quantum error-correcting codes.

Attempts To Measure Nanosecond Resolved Electronic Dynamics Of Charge Density Wave Phase Transition In 1t-Tas2, Ben Campbell

Honors Theses and Capstones

Scanning tunneling microscopes allow for atomic spatial resolution but the resulting images are necessarily time-averaged and fast dynamics are lost. Pump-probe spectroscopy is a common optical technique used to measure ultrafast electronic dynamics but the integration of optical pump-probe spectroscopy into an STM requires specialized knowledge and equipment. Alternatively, an all-electronic pump-probe spectroscopy technique has recently been developed for use with an STM that replaces the laser pulses of optical pump-probe with voltage pulses. In this paper, I implemented an all-electronic pump-probe scheme into an existing scanning tunneling microscope using an arbitrary waveform generator and a lock-in amplifier. I developed …

Functionalized Multimetal Oxideecarbon Nanotube-Based Nanocomposites And Their Properties, Mohamed Morsy

Nanotechnology Research Centre

No abstract provided.

Toward Novel Optical Functionalities Through Intelligent Photonic Structure Design, Robert J. Williamson

College of Graduate Studies: Theses & Dissertations

Photonic Metamaterials is a branch of electromagnetism that has been of great interest in recent years. This is further enhanced by the introduction of micro- and nanofabrication methods capable of producing metamaterial structures with which it is possible to create specific optical phenomena. The study of iso-frequency k-surfaces is of importance when discussing optical interactions with media. Previous research found evidence of materials exhibiting k-surfaces of bi-hyperbolic nature, though they failed to find any further hyperboloid dispersions. In this thesis we describe the k-surface topologies and including tri- and tetra-hyperbolic as well as analyze the polariton-interactions that cause these hyperbolic …

Electronic Reconstruction At The Polar (111)-Oriented Oxide Interface, S. Ryu, H. Zhou, Tula R. Paudel, Neil Campbell, J. Podkaminer, C. W. Bark, T. Hernandez, D. D. Fong, Y. Zhang, L. Xie, X. Q. Pan, Evgeny Y. Tsymbal, M. S. Rzchowski, Chang-Beom Eom

Evgeny Tsymbal Publications

Atomically flat (111) interfaces between insulating perovskite oxides provide a landscape for new electronic phenomena. For example, the graphene-like coordination between interfacial metallic ion layer pairs can lead to topologically protected states [Xiao et al., Nat. Commun. 2, 596 (2011) and A. Rüegg and G. A. Fiete, Phys. Rev. B 84, 201103 (2011)]. The metallic ion/metal oxide bilayers that comprise the unit cell of the perovskite (111) heterostructures require the interface to be polar, generating an intrinsic polar discontinuity [Chakhalian et al., Nat. Mater. 11, 92 (2012)]. Here, we investigate epitaxial heterostructures of (111)-oriented LaAlO₃/SrTiO₃ (LAO/STO). We …

Spin Hall Effect Of Vorticity, Edward Schwartz, Hamed Vakili, Moaz Ali, Alexey Kovalev

Department of Physics and Astronomy: Faculty Publications

Using mapping between topological defects in an easy-plane magnet and electrical charges, we study interplay between vorticity and spin currents. We demonstrate that the flow of vorticity is accompanied by the transverse spin current generation; an effect which can be termed as the spin Hall effect of vorticity. We study this effect across the BKT transition and establish the role of dissipation and spin nonconservation in the crossover from spin superfluidity to diffusive spin transport. Our results pave the way for low power computing devices relying on vorticity and spin flows that can propagate over long distances.

Superfluid Spin Transistor, Edward Schwartz, Bo Li, Alexey Kovalev

Alexey Kovalev Papers

We propose to use the Hall response of topological defects, such as merons and antimerons, to spin currents in two-dimensional magnetic insulator with in-plane anisotropy for identification of the Berezinskii-Kosterlitz-Thouless (BKT) transition in a transistorlike geometry. Our numerical results relying on a combination of Monte Carlo and spin dynamics simulations show transition from spin superfluidity to conventional spin transport, accompanied by the universal jump of the spin stiffness and exponential growth of the transverse vorticity current. We propose a superfluid spin transistor in which the spin and vorticity currents are modulated by changes in density of free topological defects, e.g., …

Infrared Dielectric Functions And Brillouin Zone Center Phonons Of Α-Ga2O3 Compared To Α-Al2O3, Megan Stokey, Rafal Korlacki, Matthew J. Hilfiker, Sean Knight, Steffen Richter, Vanya Darakchieva, Riena Jinno, Yongjin Cho, Huili Grace Xing, Debdeep Jena, Yuichi Oshima, Kamruzzaman Khan, Elaheh Ahmadi, Mathias Schubert

Department of Electrical and Computer Engineering: Faculty Publications

We determine the anisotropic dielectric functions of rhombohedral α-Ga₂O₃ by far-infrared and infrared generalized spectroscopic ellipsometry and derive all transverse optical and longitudinal optical phonon mode frequencies and broadening parameters. We also determine the high-frequency and static dielectric constants. We perform density functional theory computations and determine the phonon dispersion for all branches in the Brillouin zone, and we derive all phonon mode parameters at the Brillouin zone center including Raman-active, infrared-active, and silent modes. Excellent agreement is obtained between our experimental and computation results as well as among all previously reported partial information from experiment …

Tunneling Magnetoresistance In Noncollinear Antiferromagnetic Tunnel Junctions, J. Dong, X. Li, G. Gurung, M. Zhu, P. Zhang, F. Zheng, Evgeny Y. Tsymbal, J. Zhang

Evgeny Tsymbal Publications

Antiferromagnetic (AFM) spintronics has emerged as a subfield of spintronics driven by the advantages of antiferromagnets producing no stray fields and exhibiting ultrafast magnetization dynamics. The efficient method to detect an AFM order parameter, known as the Néel vector, by electric means is critical to realize concepts of AFM spintronics. Here, we demonstrate that noncollinear AFM metals, such as Mn₃Sn, exhibit a momentum dependent spin polarization which can be exploited in AFM tunnel junctions to detect the Néel vector. Using first-principles calculations, we predict a tunneling magnetoresistance (TMR) effect as high as 300% in AFM tunnel junctions with …

Generally Covariant Theory Of Multipole Moment Conserving Quasiparticles, Gavin Eric Riley

Honors Theses and Capstones

This report represents the creation of a field theory which is capable of describing quasiparticle excitations that preserve 2^k -pole moments. These quasiparticles exhibit certain ’semidynamic’ properties such as individual particle immobility but free movement of bound 2^L-tuples. We provide a review of work done on dipole conserving fractons and their dynamics [1] and expand upon it to describe higher moment conserving systems with global quadratic (and higher) phase symmetry. This requires the selection of the temporal and spatial directions. The selection of a temporal direction is done with a foliation defined by an anisotropic scaling of space and time, …