SOP

Statement of Purpose

Nam, Kee Hwan

In the future, I will be a physicist who
will be one of the most creative scientists. I want to study solid state
physics. I studied particle physics, which deals with pure quantum mechanical
system and worked in a laboratory which uses extremely strong laser and generates
high energy particles. What I notice from the experiences is that I like to
find practical to objects that I apply theories that I learned and found. Solid
state physics is appropriate for the purpose because it is easily verified by relatively
smaller scale experiments than particle physics and high power laser science as
well as knowledge in particle and laser physics is still effective and useful.
Moreover, semiconductor devices and their derived applications are becoming
more and more important for the modern world, so I can contribute to
progressing information technology. My interest is to apply theoretical method
to solid state materials and confirm it from experiments in order to understand
their physical characteristics.

My first research was neutrino
phenomenology and particle detector development in master’s course. In neutrino
physics, I studied massive neutrinos and their mixing parameters. According to
a number of neutrino oscillation experiments, the interaction eigenstates of
neutrinos are not the mass eigenstates as well as neutrinos must have non-zero
masses. This mixing is similar structure


to but much larger than that of quark sector. I
assumed a model so called “complex quark-lepton complementarity” and derived
the parameters from the model. The model is based on two ideas. One of them is
that theoretical frame explaining quark sector, Cabbibo-Kobayashi-Maskawa
matrix, is very similar to that of neutrino sector, Pontecorvo-Maki-Nakagawa-Sakata
matrix. The matrices are factorized to three elementary rotation matrices(Eulerian
rotation matrices) and one complex phase matrix. The other is that each sum of angles
corresponding to the same elementary matrix in two mixing matrices is almost
pi/4. This is called quark-lepton complementarity. Because two matrices
describes rotation in 3-dimensional complex space, the complementarity can be
generalized to the 3-dimensional complex space. In the 3-dim complex space, one
of the eigenvectors of the matrix can be taken as the axis of rotation. After
taking the axis, we can determine rotation angles of two matrices around the
axis. My argument is two angles have relation similar to Pythagorean theorem.
The relation acts as a constraint to mixing angles, so unknown mixing
parameters can be derived. The results were published in Journal of The Korean
Physical Society.

In particle detector project, my task was to
design detector chamber and to simulate electric field and particle trajactory.
The chamber was type of multiwire proportional chamber. I made the chamber
design with a computer aided design software. The chamber was operated in
vacuum because high voltage was assigned to multi-wire and poor vacuum might
cause to air breakdown.


To calculate electric
field, relaxation method to solve laplace equation were employed. After the
calculation, I made simulation code of trajactory of charged particle induced
by cosmic rays in the field. This result was presented in autumn meeting of The
Korean Physical Society at October 2006, and published in Journal of The Korean
Physical Society after I had graduated from the course.

The second research was ultra-high power
laser expreiment. When I was in Advanced Photonics Research Institute, I
participated in extremely intensive laser application experiments, which were
particle acceleration and secondary radiation generation. In the experiments, my
major tasks were to operate detectors and to analyse obtained signal. When a
target is irradiated by extremely intensive and short laser pulse, charged
particles are accelerated and secondary lights like water window x-ray and
x-ray laser are generated by interaction between laser and plasma. To
distinguish particle species, we developed Time-of-flight spectrometer and
Thomson parabola spectrometer. In the development, I did assemble, examine, calibrate,
and operate the detectors and wrote program code to diagnose characteristics of
particles: energy, current, temperature, divergence, and spectrum. Another part
of my tasks was to produce ultra-thin film of a few nm thickness to use as
laser target. I made the film with spin-coating method from an organic polymer
and multi-layer film of the polymer and metal with plasma enhanced chemical
vapor deposition devices. The film was used as a target to accelerate heavy ions
with relativistic kinetic energy. Some of the results have been published and
others are submitted to a journal and reviewing.

As shown above, I am good at dealing with
physical problems by mathematical and computational methods because I have
experienced laboratories of both of theory and experiment. Even though portion
for me to perform works related to solid state physics is small, my experience
is benefit because when I try to solve a problem, it will allow me to approach
different sight of view to traditional ways. Hence, I would propose and perform
experiments to prove my theories and arguments.

All in all, I was a generalist who is
experienced in many fields: particle, plasma, optics, and even nuclear physics
and in various methodologies: theoretical, computational, and experimental
researches. Now, I want to proceed a specialized physicist studying solid state
material. Explaining my academic objectives concretely, I want to find
mathematical structure to understand matters, to compute its physical
properties using computational tools such as density functional theory if there
is no analytic solution, and to prove it from experiments. My experiences will
be helpful to research because broad experiences should give me creative ideas
and solutions for the unsolved problems. I can prove my proficiency in
practical research. I want to be a physicist indeed. I am finding a teacher to
lead me a professional physicist and believe the teacher is in Universeity of
Texas at Austin.

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