LI, XIAOQIN

Elaine Li

Associate Professor
Department of Physics


Ultrafast nonlinear spectroscopy in condensed matter; quantum dynamics and control in nanostructures; experimentalist.
elaineli@physics.utexas.edu

Phone: 512-471-2063

Office Location
RLM 13.324

Postal Address
The University of Texas at Austin
Department of Physics, College of Natural Sciences
1 University Station C1600
Austin, TX 78712

Ph.D., University of Michigan (2003)

Research Interests

Ultrafast nonlinear spectroscopy in condensed matter; quantum dynamics and control in nanostructures; experimentalist

Spintronics, light scattering and optical wave mixing techniques, semiconductor quantum dots, mesoscopic quantum systems, laser physics, optoelectronic devices, ultrafast lasers, quantum interference effects in semiconductors, femtosecond comb technology, multidimensional spectroscopy, quantum information science.

I knew that I wanted to teach after graduating from high school. I went to Beijing Normal University thinking that I would become a high school physics teacher. While in college, one of my professors strongly encouraged me to go to the U.S. for graduate studies. I was young and very interested to see a different part of the world. I thought “what the heck, it might be fun.” So I went to the University of Michigan, where I visited some experimental research groups. My impression of the first lab I ever visited was “Boy, this place is messy!” I still decided to study experimental physics because I did not like the idea of sitting in a chair all day long. My choice of a particular lab was also based on a couple of somewhat random factors: First, I like the idea of working with lasers since I was always fascinated with laser shows. Second, I thought my advisor seemed like a kind person. He reminded me of “Santa Claus.” I was frustrated most of the time in graduate school. I now understand that all those struggles were just typical “growing pains” for a young researcher.

After spending six years at Michigan, I went to JILA in Colorado (a leading research institute for optics-related fields) as a postdoctoral fellow. I thoroughly enjoyed my years at JILA. Although I also struggled with various research projects, I was used to wrestling with scientific obstacles by then. I worked very hard during the week and spent the weekends hiking and skiing. I joined UT Austin in January 2007. I often think that I have the perfect job. I enjoy both teaching and research. It takes a lifetime of continuous effort to become both a good teacher and a good researcher. There will never be a dull moment.

What I like about physics is its universal applicability and elegance. Simple conservation laws hold at both the smallest sub-atomic scale and the largest astronomical scale. What I enjoy about research on a daily basis is that you are always solving puzzles in the lab. (Yes, I like playing Sudoku.) Although certain types of jobs in the lab are repetitive and a bit boring, the idea that my work will eventually lead to the discovery of new knowledge always excites and motivates me.

My research focuses on studies of the quantum dynamics of electrons. To meet the technical and societal challenges of the new millennium, scientists need to learn how to control material properties at the level of electrons. To see the relevance of our research, one needs to look no further than the transistor. The transistor is arguably the most important invention of the 20th century. Transistors are essentially switches, which have an “on” and an “off” state. These two states can conveniently represent binary information, which consists of only “0” and “1.” The transistor is an essential component in all electronics, including the computer you are using to access this information. The lateral size of a transistor in the first commercial microprocessor, Intel’s 4004 (released in 1971), was only about 10 microns. As a reference, the diameter of a human hair is about 100 microns. The size of a transistor has kept shrinking ever since, from 1 micron in 1985, to 0.1 micron in 2002, to tens of nanometers in current electronics. This miniaturization has enabled faster and more compact devices. If this trend continues, transistors will reach the size of individual atoms in a decade or two. What happens then? The quantum dynamics of electrons will rule! Understanding how to probe and even control electron dynamics in individual quantum systems, therefore, might hold the key to future technological challenges.

The tools used by our group to investigate electron dynamics are lasers. There are several reasons for this. First, photons are one of the most non-invasive probes. Second, we use ultrafast laser pulses, which last only ~10-13 of a second, to capture extremely fast electron dynamics in materials. Imagine that you are trying to capture a quickly moving object with a camera. You need a fast shutter. Otherwise, the image will be blurred. Ultrafast laser pulses are the shortest events ever created and measured. Finally, the phase coherent nature of lasers allows us not only to probe but also to control electron dynamics, which is a holy grail for light–matter interaction studies.

My work has been reported by various magazines including: Physics Today, Physics World, Science (News), Optics and Photonic News, New Scientists, etc.

Selected Publications

Electronic Two-Dimensional Fourier Transform Spectroscopy in Semiconductors

1. X. Li, T. Zhang, R. P. Mirin, Shaul Mukamel, S. T. Cundiff “Investigation of Electronic Coupling in Semiconductor Double Quantum Wells using Coherent Optical Twodimensional Fourier Transform Spectroscopy”, solid state communications, 149, 361-366, 2009. (2 citations)

2. Katherine W Stone, Kenan Gundogdu, Daniel B Turner, Xiaoqin Li, Steven T Cundiff and Keith A Nelson, “Two-quantum 2D Fourier Transform electronic spectroscopy of biexcitons in GaAs Quantum wells”, Science, 324, 1169, 2009. (45 citations)

3. M. Erementchouk, M. N. Leuenberger, X. Li, 2d Fourier spectroscopy of disordered quantum wells, phys. status solidi (c) 8, 1141-1144 (2011).

Yuri Glinka, Zheng Sun, Mikhail Erementchouk, Michael Leuenberger, Alan Bristow, Alan Bracker, Xiaoqin Li “Presence and Absence of Coherent Exciton Coupling in a Disordered Semiconductor Quantum Well”, in preparation

Yuri Glinka, Zheng Sun, Mikhail Erementchouk, Michael Leuenberger, Alan Bristow, Alan Bracker, Xiaoqin Li “Coherent Coupling between Delocalized Excitons in a Semiconductor Quantum Well”, in preparation

Electron Dynamics in Nanostructures

4. Suenne Kim, Daniel Ratchford, Xiaoqin Li, “Atomic Force Microscope nanomanipulation with Simultaneous Visual Guidance”, ACS Nano, 3, 2089, 2009. (6 citations)

5. Hong Wei, Daniel Ratchford, Xiaoqin Li, Hongxing Xu, and Chih-kang Shih, “Propagating Surface Plasmon Induced Photon Emission from Quantum Dots”, Nano Lett. 9, 4168, 2009. (43 citations)

6. Meg Creasey, Xiaoqin Li, J. H. Lee, Zh. M. Wang, G. J. Salamo, “Strongly Confined Excitons in Self-Assembled InGaAs Quantum Dot Clusters Produced by a Hybrid Growth Method”, J. Appl. Phys., 107, 104302, 2010. (3 citations)

7. Suenne Kim, Farbod Shafiei, Daniel Ratchford, Xiaoqin Li, “Controlled AFM manipulation of small nanoparticles and assembly of hybrid nanostructures”, Nanotechnology, 22, 115301, 2011. (1 citation)

8. Daniel Ratchford, Farbod Shafiei, Suenne Kim, Stephen, Gray, Xiaoqin Li, “Manipulating Coupling between a single semiconductor quantum dot and single gold nanoparticle”, Nano Letters, 11, 1049, 2011. (8 citations)

9. Daniel Ratchford, Konrad Dziatkowski, Thomas Hartsfield, Xiaoqin Li, Yan Gao, Zhiyong Tang, “Photoluminescence dynamics of ensemble and individual CdSe/ZnS quantum dots with an alloyed core/shell interface”, Journal of Applied Physics, 109, 103509, 2011. (2 citations)

10. Daniel Ratchford, Farbod Shafiei, Stephen, Gray, Xiaoqin Li, “Polarization properties of a CdSe/ZnS and Au Nanoparticle Dimer”, ChemPhysChem, in press, 2012.

Megan Creasey, Xiaoqin Li, J. H. Lee, Zh. M. Wang, G. J. Salamo, “Self-Assembled InGaAs/GaAs quantum dot molecules with controlled spatial and spectral properties” submitted

Farbod Shafiei, Chihhui Wu, Patrick Putzke, Yanwen Wu, Akshay Singh, Xiaoqin Li, Gennady Shvets “Plasmonic Nano-Protractor Based on Polarization SpectroTomography”, in preparation

Farbod Shafiei, Francesco Monticone, Le Quang Khai, Xing-Xiang Liu, Tom Hartsfield, Andrea Alu, Xiaoqin Li, “Artificial Magnetic Molecules at the Optical Frequencies”, in preparation

Spin Dynamics in Magnetic Microstructures

11. Daniel R. Birt, Brian O’Gorman,Maxim Tsoi, Xiaoqin Li, Vladislav E. Demidov, and Sergej O. Demokritov, “ Diffraction of spin waves from a submicrometer-size defect in a microwaveguide”, Appl. Phys. Lett. 95, 122510, 2009. (5 citations)

12. Vladislav E. Demidov, and Sergej O. Demokritov, Daniel R. Birt, Brian O’Gorman,Maxim Tsoi, and Xiaoqin Li, “ Radiation of spin waves from the open end of a microscopic magnetic-film waveguide”, Phys. Rev. B., 80, 014429, 2009. (10 citations)

Daniel R. Birt, Kyongmo An, Kin Wong, Kang Wang, Maxim Tsoi, Xiaoqin Li “Deviation from Exponential Decay for Spin Waves Excited with an Coplanar Waveguide Antenna”, in preparation Linear and Nonlinear Optical Processes in Materials

13. Shengyuan Yang, Xiaoqin Li, Alan Bristow, and J. E. Sipe, “Second Harmonic Generation from tetragonal centrosymmetric crystals”, Phys. Rev. B., 80, 165306, 2009. (3 citations)

14. Xuhuai Zhang, Marcelo Davanco, Kara Maller, Thomas Jarvis, Chihhui Wu, Dmitriy Korobkin, Yaroslav Urzhumov, Xiaoqin Li, Gennady Shvets, Stephen R. Forrest, “Interferometric characterization of a sub-wavelength near-infrared negative index metamaterial”, Opt. Exp.18, 17788, 2010. (2 citations)

 

 

  • Presidential Early Career Award for Scientists and Engineers (PECASE), 2009
  • Alfred P. Sloan Research Fellowship 2008-2011
  • NSF CAREER AWARD 2008
  • AFOSR YIP AWARD 2008
  • ONR YIP AWARD 2008
  • Rackham Graduate School One Term Dissertation Fellowship, 2003,
  • Alfred P. Sloan Summer Research Fellowship, 1999
  • Academic Excellence Awards: 1993-1997
  • ShuPing Fellowship: 1992-1995