Research




Ongoing Projects


Magnetic neutron diffraction of CeAuSb2 (Experiment)

Collaborators: Prof. Collin Broholm (PI) and colleagues at the Institute for Quantum Matter 

Synthesis and characterization of skyrmion materials (Experiment)

Collaborators: Prof. Collin Broholm (PI) and colleagues at the Institute for Quantum Matter


Gauge field theory of the skyrmion (Theory)

Collaborators: Prof. Oleg Tchernyshyov (PI)


Past Projects



Measurements of the Lagrangian Rotational Dynamics of Anisotropic Particles in Turbulence (Experiment)


 We measure the Lagrangian rotational dynamics of anisotropic particles in turbulent flow with stereoscopic video imaging. The canonical shapes that we choose to study are rods, crosses (two perpendicular rods), and jacks (three mutually perpendicular rods), which we design and fabricate using 3D printing technology. The three dimensional position of particles is measured using stereomatching techniques. Furthermore, we have developed a general methodology for measuring the time-resolved Lagrangian orientation and solid body rotation rate of anisotropic particles in a turbulent flow. 

We apply these techniques to measurements in a Rλ ≈ 110 flow, where turbulence is generated by two grids oscillating in phase. Since the advected particles have a largest dimension less than 10 times the Kolmogorov length, they are good approximations of tracer particles. Using resistive force theory, we demonstrate that ideal tracer jacks and crosses have the same rotational dynamics as spheres and disks, respectively. Thus, our measurements allow us to probe the dependence of the rotation rates of ellipsoidal particles on aspect ratio (α) at qual- itatively distinct points spanning the entire range: α = 0 (measured by disks), α = 1 (jacks), and α = ∞ (rods). 

Our measurements of the alignment of crosses with the direction of their solid body rotation rate vector are the first direct observation of the alignment of anisotropic particles by the velocity gradients in the flow. Our measurements of jacks provide a way to directly probe the vorticity of the fluid and vortex structure in the flow. Our measurements of the mean square rotation rate spanning the range of aspect ratios agrees with DNS data of the same quantity and represents a cohesive understanding of the rotational dynamics of anisotropic particles in turbulence. 


Collaborators: Prof. Greg Voth (PI), Dr. Shima Parsa, Dr. Rui Ni, Stefan Kramel

 

Jack in a Turbulent Flow






Transient Antihydrogen Production in a Paul Trap (Theory)


 Although positrons and antiprotons have vastly different masses, we show that it is possible to store both particle species simultaneously in a Paul trap, using the space charge of the positron cloud as a trap for the antiprotons. Computer simulations confirm the validity of this new trapping mechanism. In addition, the simulations show transient antihydrogen production that manifests itself in the intermittent production of bound positron-antiproton Rydberg states. Since realistic trapping parameters are used in the simulations, (i) simultaneous positron-antiproton trapping and (ii) transient antihydrogen formation should be experimentally observable in a Paul trap. Strategies are suggested to lengthen the lifetime of antihydrogen in the Paul trap.

Collaborators: Prof. Reinhold Blümel (PI)
 



"Genuine" Quantum Chaos (Theory)

Quantum mechanics is linear and unitary. As such, a wavefunction of a proper Hamiltonian will not experience any separation from a slightly perturbed wavefunction. In the literature, this argument has been shown to fail when a quantum system is coupled to a classical one. We conceive and theoretically investigate a novel mechanism for introducing chaos into a fully quantum treatment of a quantum particle in a modification of the infinite square-well similar to a semi-quantum version that has been studied in the literature.

Collaborators: Prof. Reinhold Blümel (PI), YunSeong Nam


Heating of Non-Neutral Plasmas in a Paul Trap (Theory)


Following a line closely related to my previous work on antihydrogen synthesis in Paul traps, we explore the nature of the radio-frequency heating mechanism in Paul traps. We introduce a novel method to theoretically probe the heating rate of ion clouds and present a model to analytically explain the behavior we observe in our numerical simulations.

Collaborators: Prof. Reinhold Blümel (PI), Eric B. Jones, Jesse Tarnas, YunSeong Nam























































































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