Physics Colloquium Fall 2022

Thursdays 4:00 p.m. 104 Physics or online via Zoom.

Contact colloquium organizer Dr. Hyunsoo Kim at for the Zoom link.

(Link to main colloquium page)


A technical ecosystem to enable multi-messenger astrophysics

With the detection of compact binary coalescences and their
electromagnetic counterparts by gravitational-wave detectors, a new
era of multi-messenger astronomy has begun. In this talk, I will
describe how GW170817, our first example in this new class, is being
used to constrain the unknown equation of state of cold supranuclear
matter, and to measure the Hubble constant. I will then discuss how
current ground based optical surveys and dedicated follow-up systems
are being used to identify more of these, and how we are developing
models to test what we find. We will close with near-term prospects
for the field.

Radiation Effects in Ceramics: Core Concepts and Recent Developments
Since the dawn of the nuclear era, ionizing radiation has been known to bring about profound changes to the structure and properties of solids. Energy transfer from neutrons, gamma-rays, beta particles, and swift ions to matter produces atomic and electronic defects. In ceramic materials – a broad class of materials spanning many crystal structures, bond types, and often exhibiting noteworthy material properties – nuclear collisions and electronic excitation processes must be understood to predict material performance in intense radiation environments, such as those found in nuclear fission reactors, nuclear fusion reactors, outer space, and particle accelerators.  
This colloquium talk will introduce the fundamental radiation matter interactions and damage production mechanisms. Recent advances in our understanding of how atomic-scale structural disorder couples to electronic excitation and how electronic excitation produces structural disorder will also be examined. Throughout the presentation, experimental facilities and techniques used to produce damage, characterize radiation effects, and manufacture novel materials will be highlighted.




My group applies trace gas detection methods for the quantification of trace gases, these include wavelength modulation spectroscopy, frequency comb spectroscopy and cavity ring-down spectroscopy. Both long pathlengths and local measurements are being performed. Particular attention is placed on the detection of such gases of interest as methane, acetone and carbon dioxide.

Several of these gases are also present in exhaled human breath and were spectroscopically identified and related to certain health conditions, in particular diabetes and lung cancer.

In this talk I report on the sensitive and high-resolution spectral methods of trace gas detection (down to sub-ppb level) and various applications of this methods in atmospheric and biomedical physics.

 Ultrafast LIDAR and its Biomedical Applications


Optical fibers have applications in various fields, including subsea and data center communication systems, fiber lasers and sensors, remote sensing as well as biomedical applications, among others. In this talk, I will first talk about the different projects undergoing in my laboratory including acoustic sensors, few-mode fiber devices, and high-resolution motion detection sensors. I will then talk about a fiber-based LIDAR system designed to achieve nanometer resolution for medical applications.

Since slight head motion can result in inaccurate imaging and radiation dose delivery to tumors that may harm surrounding healthy tissues in the intracranial region, it increases the demand for high spatiotemporal motion detection during stereotactic radiotherapy even when the patient’s head is under a thermoplastic mask. The motion detection under a thermoplastic mask and during the surgery necessitates developing a sensor that (1) is miniaturized and fits under the mask, (2) is small enough not to cause attenuation in radiation beams, (3) has a spatial resolution of a tenth of a mm, (4) is real-time, and (5) is immune to electromagnetic radiation. We report a fiber-optic-based ultrafast spectral laser detection and ranging (LIDAR) sensor that satisfies all the above requirements.

Title: Quantum computing of molecular orbitals and vibrational energy levels

Abstract: Quantum computers are promising tools for the simulation of large molecular systems which are intractable using classical computers. However, the currently available quantum computers are noisy, which leads to errors in the calculations. To obtain meaningful results, the error must be mitigated.
In this talk, following an introduction to quantum computing, I will discuss our recent attempts to calculate molecular properties using quantum computers. I will show how vibrational energy levels of CO2 can be evaluated [1,3], and introduce the quantum computing of Hückel molecular orbitals [2]. We run our simulations on IBM’s superconducting qubit type quantum computer ibm_kawasaki, installed last year in Shin-Kawasaki outside Tokyo.

[1]    E. Lötstedt, K. Yamanouchi, T. Tsuchiya, and Y. Tachikawa, Physical Review A 103, 062609 (2021).
[2]    R. Yoshida, E. Lötstedt, and K. Yamanouchi, The Journal of Chemical Physics 156, 184117 (2022).
[3]    E. Lötstedt, K. Yamanouchi, and Y. Tachikawa, AVS Quantum Science 4, 036801 (2022).

Two-phase superconductivity and hidden order in the locally noncentrosymmetric CeRh2As2

The recently discovered CeRh2As2 superconductor with the transition temperature of Tc = 0.26 K has been attracting attention [1]. An unusual shape of upper critical field (Hc2) phase diagram and a thermodynamic phase transition within the superconducting (SC) state reveal two separated SC phases. This is characterized by a transition from a low-field (pseudo)spin-singlet to a high-field (pseudo)spin-triplet state. In the normal state, moreover, in-depth high-field measurements establish a rich phase diagram for the hidden order at T0 = 0.4 K. This is attributed to a peculiar quadrupolar density wave order of the electronic Ce-4f moments [2]. In this talk, I would like to explain how these exotic phenomena can be related to the local crystal/electronic structure of the Ce atom in the lattice.

[1] S. Khim, J. Landaeta et al, Science 373, 1012 (2021). 

[2] D. Hafner et al., Phys. Rev. X 12, 011023 (2022). 

A Physicist's Journey into Cancer Research

Cancer will affect approximately 2 in 5 Americans in their lifetime, of which half will be at risk of premature death. Early, in the 20th century, treatments for this disease focused on blunt therapies often severely hampering the quality of life while offering only moderate increases in survival rates. Later in the 20th century continued research both on and off the bench began to identify improved therapies. However, it was not until the turn of the century--enabled by advances in in vitro techniques borrowed from the cell along with novel computational applications, did the newest therapies begin to focus on genomic diagnostics. These advances are now allowing for more personalized and improved quality-of-life treatments. In this talk, I will discuss my evolution from physics to cancer research and the role I play in the central hypothesis guiding these advanced treatments.
Short Bio:
Bernard Fendler is a Computational Biologist at Foundation Medicine, a cancer diagnostic company. Bernard has a background in physics with a longstanding love of the biological sciences. After receiving his PhD in Biophysics at Florida State University, Bernard was awarded a postdoctoral fellowship at Cold Spring Harbor Laboratory focusing on computational research in genomic analyses. After his postdoctoral work, Bernard began working in cancer diagnostics, first at the Brigham and Women’s Hospital and now at Foundation Medicine as a Computational Biologist. Currently, Bernard specializes in the identification of aberrations in cancer genomes and modeling of Next Generation Sequencing data.
James Webb Space Telescope and Galaxies in the Early Universe
The James Webb Space Telescope (JWST) is a large infrared space telescope developed by NASA, ESA, and CSA. By taking advantage of its large 6.5-meter mirror, JWST achieves 10-1000 times higher sensitivities than other previous telescopes in the infrared, allowing us to observe the star/planet formation and galaxies in the early universe. Astronomers had been eagerly awaiting the start of JWST since its project began around 1990, and its observations finally began in the summer of 2022. Now many astronomers around the world are excited about JWST's data obtained, and several surprising discoveries are already reported. In this talk, I will give an overview of the James Webb Space Telescope and then explain what we have learned so far and what we are likely to learn in the near future, focusing on observational studies of galaxies in the early universe.

Title: Superconductivity in a dying Fermi sea


Superconductivity in elemental metals such as Hg and Al forms out of a gas of long-lived electron-like excitations.  It has been well understood for nearly 6 decades within the framework of Bardeen, Cooper and Schrieffer (BCS) theory.  By contrast, many  “strongly correlated” materials, such as the cuprates, heavy fermion systems, and iron pnictide materials, host superconductivity that condenses out of strongly interacting metals without long-lived electronic excitations.  The manner in which such a short-lived, “dying” sea of electrons gives way to enhanced superconductivity has remained one of the most challenging and exciting questions of modern condensed matter theory. 


In this talk, I will review some of the fascinating experimental developments that point towards the simultaneous enhancement of superconductivity and the destruction of long-lived electron excitations.  Both these effects tend to occur near continuous T = 0 phase transitions known as quantum critical points.  I will discuss ongoing efforts to describe the manner in which superconductivity arises in metals close to quantum critical points.

CSI: Gravity - Investigating fundamental physics with gravitational waves

The detection of nearly 100 gravitational wave signals produced by coalescing black holes or neutron stars have opened a rich discovery space for astrophysics, fundamental physics and cosmology. They enable qualitatively new tests of gravity in its most extreme regime that unfolds when black holes collide. To link gravitational wave observations to extensions of general relativity, and to infer parameters of the underlying theory of gravity, we need accurate waveform models in and beyond general relativity. In this talk, I will give you an overview of new black-hole observations, I will give you a brief introduction to numerically modelling binary black holes, and I will highlight new dynamical phenomena that are absent in GR.


Title: When random walk is not so random: Coherent control of wave propagation in opaque materials

Abstract: The concept of diffusion is widely used to describe propagation of light through multiple scat-
tering media such as clouds, interstellar gas, colloids, paint, biological tissue, etc. Such media are of-
ten called random. This terminology is, however, misleading. Notwithstanding its complexity, the
process of wave propagation is entirely deterministic – uniquely defined by the exact positions of
scattering centers and the shape of the incident wavefront – making it possible to deduce the precise
pattern of wave field throughout the system. Technological advances over the last decades enabled
one to synthesize an arbitrary wavefields opening new frontier in light control inside strongly scattering media.
Feasibility of the coherent control necessitates a general framework for predicting and under-
standing the ultimate limit for a targeted energy delivery into a diffusive system. In this talk, we will
discuss such scientifically and technologically important questions as “How can one systematically
find the incident wavefront that optimally deposits energy into a target?” and “What is the ultimate
limit on the energy enhancement in a region?” Predictable energy delivery opens the door to numerous applications, e.g., optogenetic control of cells, photothermal therapy, as well as probing and manipulating photoelectrochemical processes deep inside nominally opaque media.

Gaurav Khairnar
“Phases and Phase Transitions of the Disordered q-state Quantum Clock model”

Jose Nicasio
“Dispersion of Ultra-Relativistic Tardyonic and Tachyonic Wave Packets on Cosmic Scales”

Ali Sarikhani
“Transparency and room temperature ferromagnetism in diluted magnetic polycrystalline Zn1−xCrxTe non-oxide II-VI semiconductor compounds”

Yanyan Zheng
“An Optically Targeted Search for Gravitational Waves emitted by Core-Collapse Supernovae during the Third Observing Runs of Advanced LIGO and Advanced Virgo”