The quantum theory of matters is the foundation for modern electronic and energy-conversion devices that have emerged and altered the course of human history over the past seven decades. The ultimate performance and energy efficiency of existing solid-state devices will soon be limited by the relatively well understood behaviors of commonly used simple periodic crystals and highly disordered structures. On the other hand, extraordinary quantum transport phenomena are being discovered in novel materials including nanostructures and complex superstructures that contain low-dimensional substructures. These emerging classes of quantum materials hold promise for revolutionary device technologies that can enable sustainable use of energy and improve the quality of life.
The goal of our research is to accelerate the discovery and understanding of electronic and quantum materials for device and system technologies that can contribute to a sustainable global society. Our current research includes the following topics:
- Ultrahigh thermal conductivity materials
- Electronic switching of thermal properties
- Spintronics and spin caloritronics
- Two-dimensional materials and devices
- Thermoelectric materials and devices
- Topological insulators and superconductors
Our materials research is motivated by some of the grand technological challenges in areas including:
- Computing power and energy efficiency of solid state devices, which are projected to require more electrical power than the world can generate by 2040 unless radical improvement in the energy cost per data bit can be made;
- Electricity generation from waste heat, which amounts to over 60% of fuel energy consumption of transportation vehicles and between 20% to 50% of industrial energy input;
- Efficient heating and cooling of buildings and vehicles, which consumes as much as 20% of US energy supply;
- Concentrated solar power, which is receiving renewed interest because thermal energy storage can be employed to address the intermittency of solar flux.
We seek to break the current limits of legacy technologies, especially along the following directions:
- In existing and emerging electronic, optoelectronic, and photovoltaic devices, the limited electron and thermal transport properties of semiconducting, metallic, dielectric, and polymeric materials result in high heat dissipation densities and local hot spots. Novel materials with ultrahigh electron mobility or ultrahigh thermal conductivity can significantly enhance the energy efficiency, performance, and thermomechanical reliability of these solid-state electronic and energy conversion devices. Moreover, emerging topological, superconducting, and magnetic superstructures may enable disruptive quantum information technologies to realize powerful quantum computing, secure quantum communication, and energy-efficient high-density data storage.
- For electricity generation from waste heat, rapid progresses have been made to increase the figure of merit (ZT) of PbTe and Bi2Te3 materials for solid-state thermoelectric energy conversion based on the Seebeck and Peltier effects. However, these materials contain either rare or toxic elements. If the ZT of other non-toxic materials made of earth-abundant elements can be enhanced to exceed the state of the art, or other novel and efficient thermal-to-electric conversion mechanisms including spin-mediated thermoelectric conversion processes can be discovered, it may enable widespread use of compact, efficient, and reliable solid-state thermoelectric devices for vehicle waste heat recovery at a scale commensurate to the global vehicle manufacturing enterprise. Meanwhile, materials with ultralow thermal conductivity can enable low-energy loss windows for buildings, and many other applications in addition to efficient solid-state thermoelectric devices.
- For thermal energy storage, the energy density and power capacity are limited by the low latent heat and thermal conductivity values of existing storage media, such as inorganic salts, organic compounds, and their eutectics. Novel thermal storage materials and devices with enhanced energy density and power capacity can lower the cost of large-capacity concentrated solar power plants, drastically increase the use of roof-top solar thermal systems, and enable compact heating and cooling devices for thermal management of buildings, electric vehicles, electronic devices, electrochemical energy storage systems, and concentrated photovoltaic systems.
- In concentrated solar thermal power systems, the exergy efficiency can be increased considerably by reducing the temperature drop between the heat transfer fluid and the thermal storage medium to minimize entropy production, and by increasing the thermal receiver temperature if thermally stable solar absorption coating materials and heat transfer fluids can be developed, or a high-efficiency solid-state thermoelectric or thermionic topping cycle can be integrated.
Our past research has demonstrated a set of unique methods based on nanofabricated measurement devices, scanning probe microscopy, and optical spectroscopy to characterize the transport and conversion of quantized energy carriers in nanostructures and complex superstructures. Our investigations have led to a better understanding of the extraordinary quantum transport phenomena in emerging materials for thermal management, thermal energy storage, solid-state thermoelectric energy conversion, spin caloritronics, and spintronics. In particular, our work has advanced the frontier of ultrahigh thermal conductivity materials, including carbon nanotubes, graphene, hexagonal and cubic boron nitride, and cubic boron arsenide. Meanwhile, our research has made positive impact on the studies of thermoelectric, topological, and spintronic materials such as semiconducting chalcogenides, incommensurate chimney ladder and spin chain compounds, and ferromagnetic garnets. Our adventure into nanotechnologies for drug delivery and biomedical imaging has also produced noteworthy results, for example, shape-specific polymeric drug carriers manufactured by nano-imprint lithography.
Our current research efforts are focused on electronic and quantum materials for future-generation energy-efficient devices and quantum information technologies. The common theme of these multidisciplinary investigations is to understand and control the transport, conversion, and storage of heat, electricity, light, and magnetization from the macroscale down to the nanoscopic level of quantized energy excitations, including photons, phonons, electrons, and spins. These efforts involve theory-guided synthesis, characterization, and device integration of advanced materials, as highlighted by our recent experimental validation of boron arsenide (BAs) as the first known semiconductor with a ultrahigh thermal conductivity and illustrated in our current and past projects listed below:
- Materials with Extreme Phononic Coupling
- Graduate Student Researchers: Hwijong Lee, Chuting Chai
Collaboration: Profs. Feliciano Giustino, Jianshi Zhou
Sponsor: NSF MRSEC Center for Dynamics and Control of Materials
Period: 09/2021-08/2023 - Extraordinary Electronic Switching of Thermal Transport
- Graduate Student Researchers: Devika Mehta, Emma Peavler, Chuting Chai, Yajie Huang
Collaboration: Profs. Joshua Goldberger, Joseph Heremans, David Johnson, Phillip Kim, Allan MacDonald, Arun Majumdar
Sponsor: Office of Naval Research MURI
Period: 06/2021-06/2024
- Nanofabrication, Modeling, and Characterization of Nano-mechanical/phononic/photonic Devices
- Post-doctoral Researcher: Dr. Brandon Smith
Collaboration: Dr. Matt Eichenfield
Sponsor: Sandia National Laboratories
Period: 11/2020-06/2021
- High-Order Phonon Scattering and Highly Nonequilibrium Carrier Transport in Two-dimensional Electronic and Optoelectronic Materials
- Graduate Student Researcher: Peter Sokalski
Collaboration: Prof. Xiulin Ruan (Purdue University)
Sponsor: National Science Foundation
Period: 07/2020-06/2023
- Collective Energy Transport of Excitons in Two-dimensional Materials
- Graduate Student Researcher: Yajie Huang
Collaboration: Prof. Steve Cronin (USC)
Sponsor: Department of Energy Office of Science
Period: 06/2019-05/2022
- Magnetism and Spin/Heat Coupling in Moiré Superstructures
- Post-doctoral & Graduate Student Researchers: Devika Mehta, Dr. Sean Sullivan, Dr. Xi Chen
Collaboration: Profs. Allan MacDonald, Emanuel Tutuc, Roberto Meyers, Joseph Heremans
Sponsor: Army Research Office
Period: 09/2018-09/2019
- Hydrodynamic Thermal Transport in Graphitic Materials
- Graduate Student Researchers: Eric Ou, Sean Sullivan, Jihoon Jeong
Collaboration: Prof. Yaguo Wang, Prof. Sangyeop Lee (University of Pittsburgh)
Sponsor: National Science Foundation
Period: 08/2017-07/2020 - Graduate Student Researchers: Evan Fleming, Sally Jia
Collaboration: Prof. Donglei Fan
Sponsor: National Science Foundation
Period: 09/2016-08/2019
- Energy Carrier Transport in Functionalized Two-Dimensional Layered Chalcogenides
- Graduate Student and Post-doctoral Researchers: Hwijong Lee, Dr. Mir Mohammad Sadeghi
Collaboration: Prof. Steve Cronin (USC)
Sponsor: Department of Energy Office of Science
Period: 06/2016-05/2019
- Ultrahigh Thermal Conductivity Materials
- Graduate Student and Post-doctoral Researchers: Yuanyuan Zhou, Hwijong Lee, Dr. Jaehyun Kim, Dr. Xi Chen, Dr. Sean Sullivan
Collaboration: Profs. David Broido (Boston College), David Cahill & Pinshane Huang (UIUC), Gang Chen (MIT), Ni Ni (UCLA), Zhifeng Ren (University of Houston), Bing Lv (University of Texas at Dallas), Jianshi Zhou (UT Austin)
Sponsor: Office of Naval Research MURI Program
Period: 06/2016-10/2021
- Graphitic Coatings and Porous Networks for Vehicle Thermal Management
- Graduate Student and Post-doctoral Researchers: Evan Fleming, Dr. Iskandar Kholmanov
Sponsor: Toyota Motor Corporation
Period: 04/2016-03/2017
- Probing Thermal Transport in Three-Dimensional Pillared Graphene Structures
- Graduate Student and Post-doctoral Researchers: Evan Fleming, Dr. Iskandar Kholmanov
Collaboration: Profs. Liming Dai (CWRU), Dr. Xiulin Ruan (Purdue), Dr. Ajit Roy (ARFL)
Sponsor: Airforce Office of Scientific Research MURI/Case Western Reserve University
Period: 09/2015-11/2017
- EFRI 2-DARE: Enhancing Electronic and Thermal Properties in Epitopotaxial Ge/Sn Graphane Heterostructures
- Graduate Student Researcher: Gabriella Coloyan, Devika Mehta
Collaboration: Profs. Joshua Goldberger (OSU), David Broido (Boston College), David Cahill (UIUC), Joseph Heremans (OSU)
Sponsor: National Science Foundation
Period: 09/2014-03/2020
- Development of Light Scattering Characterization Equipment for the Study of Magnon and Phonon Dynamics in Materials with Spin/Heat Coupling
- Collaboration: Prof. Elaine Li (UT Austin)
Sponsor: Army Research Office Defense University Research Instrumentation Program (DURIP)
Period: 06/2014-06/2015
- Size-dependent Phonon Transport in Boron Arsenide with Potentially Record-high Thermal Conductivity
- Post-doctoral & Graduate Student Researchers: JaeHyun Kim, Dan Evans, Owen Williams, Dr. Dan Sellan
Collaboration: Prof. Alan Cowley (UT Austin)
Sponsor: Office of Naval Research
Period: 06/2014-09/2017 - Fully Integrated 2D Nanomaterials for High-Performance Flexible Nanoelectronics
- Graduate Student Researcher: Brandon Smith
Collaboration: Prof. Deji Akinwande (UT Austin)
Sponsor: Office of Naval Research
Period: 01/2014-12/2017 - Probing Highly Non-equilibrium Thermal Transport in Nanostructures and Devices
- Graduate Student Researchers: Kevin Olsson, Sean Sullivan, Annie Weathers
Collaboration: Prof. Elaine Li (UT Austin)
Sponsor: National Science Foundation
Period: 09/2013-08/2017 - Materials with Extraordinary Spin/Heat Coupling
- Post-doctoral & Graduate Student Researchers: Dr. Annie Weathers, Dr. Xi Chen, Sean Sullivan, Dr. Kyongmo An
Collaboration: Profs. Roberto Meyers, Joseph Heremans (Ohio State University), David Cahill (UIUC), David Awschalom (Univ of Chicago), Yaroslav Tserkovnyak (UCLA), Elaine Li (UT Austin), Jianshi Zhou (UT Austin) Sponsor: Army Research Office Multidisciplinary Uiversity Research Intitiative (MURI)
Period: 12/2013-09/2019 - Phonon and Electron Transport in Pristine Two-Dimensional Layered Nanostructures and Heterostructures
- Graduate Student Researchers: Gabriella Coloyan, Eric Ou
Collaboration: Prof. Steve Cronin (USC)
Sponsor: Department of Energy Office of Basic Energy Science
Period: 06/2013-05/2016 - NSF Nanosystems Engineering Research Center: Nanomanufacturing Systems for Mobile Computing and Devices (NASCENT)
- Graduate Student Researchers: Qianyu (Sally) Jia, Brandon Smith, Gabriella Coloyan, David Choi, Mir Mohammad Sadeghi
Collaboration: Profs. Deji Akinwande, Jayathi Murthy
Sponsor:National Science Foundation
Period: 09/2012-08/2020 - MRI: Acquisition of a Spark Plasma Sintering System for Engineering Advanced Energy Materials and Materials Science Education
- Collaboration: Profs. Jianshi Zhou, John Goodenough, Arumugam Manthiram, Desiderio Kovar (UT Austin)
Sponsor: National Science Foundation
Period: 09/2012-06/2015 - Thermal Batteries for Electric Vehicles
- Post-doctoral & Graduate Student Researchers: Evan Fleming, Dr. Hengxing Ji, Dr. Abhijit Paul, Dr. Daniel Sellan, Dr. Shaoyi Wen, Dr. Eunsu Paek, Dr. Iskandar Kholmanov
Collaboration: Profs. Chris Bielawski, Alex da Silva, Rodney S. Ruoff, Jayathi Murthy, Gyeong Hwang, Dr. Peng Zhou, Dr. Dolf van der Heide
Sponsor: Department of Energy ARPA-E
Period: 11/2011-6/2015 - Topological Insulator Coherent Energy Devices
- Post-doctoral and Graduate Student Researchers: Dr. Michael Pettes, JaeHyun Kim
Sponsor: Defense Advanced Research Project Agency (DARPA) / Purdue University
Period: 06/2011-06/2015 - High-Performance Thermoelectric Devices based on Abundant Silicide Materials for Vehicle Waste Heat Recovery
- Graduate Student Researchers: Chad Baker, Xi Chen, Haiyan Fateh, Daniel Salta, Libin Zhang
Collaboration: Profs. J. B. Goodenough, M. J. Hall, J. S. Zhou (UT Austin), J. Song (University of Wisconsin-Madison)
Sponsor: National Science Foundation & Department of Energy Joint Thermoelectric Partnership
Period: 10/2010-05/2015 - Energy Transport in Graphene
- Graduate Student Researchers: Michael T. Pettes, Insun Jo, Mir Mohammad Sadeghi, Gabbi Coloyan
Collaboration: Prof. Steve Cronin (USC)
Sponsor: Department of Energy Office of Basic Energy Science
Period: 06/2010-05/2013 - Ballistic and Quantum Thermal Transport Phenomena and Devices
- Postdoctoral and Graduate Researchers: Dr. Jae Hun Seol, Dr. Arden Moore, JaeHyun Kim, Eric Ou
Sponsor: Office of Naval Research
Period: 02/2010-01/2013 - High-Throughput Nanoimprint Fabrication of Shape-Specific, Stimuli-responsive Polymeric Nanocarriers for Drug and Imaging Agent Delivery
- Graduate Student Researchers: Mary C. Moore, Vikramajit Singh, Patrick Jurney, Rachit Agarwal, Scott Marshall, David Choi
Collaboration: Prof. S.V. Sreenivasan (UT Austin), Prof. K. Roy (UT Austin), Dr. D. LaBrake (Molecular Imprint, Inc)
Sponsors: National Science Foundation
Period: 07/2009-09/2013 - Electronic Thermal Transport in Nanoscale Conductors
- Graduate Student Researchers: Mir Mohammad Sadeghi, Jae Hun Seol, Annie Weathers
Sponsor: National Science Foundation
Period: 07/2009-06/2013 - Characterization of Nanostructured Thermoelectric Materials
- Post-doctoral & Graduate Researchers: Dr. Arden Moore, Dr. Huijun Kong, Dr. Yong Lee, Dr. Michael Pettes, JaeHyun Kim
Sponsor: Office of Naval Research
Period: 07/2008-09/2011 - Shape Specific, Enzyme-Responsive, Nano-Imprinted Particles for Drug Delivery
- Graduate Student Researchers: Mary C. Moore, Rachit Agarwal, JaeHyun Kim
Collaboration: Prof. K. Roy (UT Austin)
Sponsors: National Institute of Health
Period: 07/2008-06/2011 - Batch-Fabricated Nanowire Plasmonic Probes for Near Field Imaging of Single Molecules and Cells
- Graduate Student Researcher: JaeHyun Kim
Post-doctoral Researcher: Dr. Yong Lee
Sponsor: Texas Higher Education Coordinating Board Norman Hackerman Advanced Research Program
Period: 05/2008-05/2010 - Structure-Optical-Thermal Relationships of Carbon Nanotubes
- Graduate Student Researchers: Michael T. Pettes, JaeHyun Kim
Collaboration: Prof. Steve Cronin (USC)
Sponsor: Department of Energy Office of Basic Energy Science
Period: 06/2007-05/2010 - Catalyst Substrates with Nanoscale Features for Enhanced Reaction Activity
- Graduate Student Researcher: Chad Baker
Collaboration: Prof. M. J. Hall (UT Austin)
Sponsor: Texas Hazardous Waste Research Center
Period: 09/2007-08/2010 - High Temperature and Magnet Cryostats for Characterization of Nanowire and Thin Film Thermoelectric Materials
- Sponsor: Office of Naval Research
Period: 05/2007-09/2008 - Thermal Transport at Nanoscale Point and Line Constrictions and Interfaces
- Graduate Student Researchers: Jae Hun Seol, Arden L. Moore, Nathan Malcolm, Sanjoy Saha
Collaboration: Prof. John R. Howell (UT Austin), Dr. Ravi S. Prasher (Intel)
Sponsor: National Science Foundation
Period: 09/2006-08/2010 - NER: Nanoimprint Fabrication of Stimuli-responsive Drug Delivery Carriers
- Graduate Student Researchers: Luz Cristal Glanchai, Mary C. Moore
Collaboration: Prof. K. Roy (UT Austin)
Sponsors: National Science Foundation
Period: 08/2006-07/2007 - Room-Temperature Scanning Single-Electron-Transistor Microscopy of Nanoelectronic Devices
- Gradate Student Researcher: Michael T. Pettes
Post-doctoral Researcher: Dr. Yong Lee
Collaboration: Prof. Zhen Yao (UT Austin)
Sponsor: Texas Higher Education Coordinating Board Norman Hackerman Advanced Research Program
Period: 08/2006-07/2008 - Nanowire Composite Peltier Coolers
- Graduate Student Researcher: Arden L. Moore
Sponsor: DARPA Advanced Processing and Prototyping Center (AP2C)
Period: 11/2005-11/2006 - Investigation of Electrical Conductivity of Silicide and Copper Nanowires
- Gradate Student Researcher: Bin Li
Collaboration: Prof. Paul S. Ho (UT Austin)
Sponsor: National Institute of Standards & Technology
Period: 06/2005-05/2006 - Nanowire Composites for Energy Efficient Thermoelectric Refrigeration and Power Generation in Space Applications
- Graduate Student Researchers: Feng Zhou, Jae Hun Seol
Collaborations: Dr. Laura Ye, Dr. Natalio Mingo, NASA Ames Research Center
Sponsor: NASA through Eloret Corporation
Period: 05/2005-05/2007 - Directed Assembly of Metal Oxide Nanowires with Microsystems for Sensor Applications
- Graduate Student Researcher: Choongho Yu
Collaboration: Prof. Z. L. Wang (Georgia Institute of Technology)
Sponsor: UT Research Grant Program Period: 09/2004-08/2005 - Novel Nano and Micro-fabrication Methods for Injectable, Tissue-targeted, Stimuli-responsive Delivery Vehicles: Towards Simultaneous Delivery of Therapeutics and Contrast-agents
- Graduate Student Researchers: Luz Cristal Glanchai, Mary C. Moore
Collaboration: Prof. K. Roy (UT Austin)
Sponsors: Charles W. Tate & Judy Spence Tate Charitable Foundation through UT Center for Biomedical Engineering
Period: 09/2004-08/2005 - Nanoconductors for Future Interconnects and Air Bridge Interconnects
- Graduate Student Researcher: Bin Li, Anastassios Mavrokefalos
Collaboration: Prof. Paul S. Ho, Zhen Yao, Rui Huang (UT Austin)
Sponsor: SEMATECH
Period: 09/2004-08/2006 - YIP: Characterization of Nanostructures for Efficient Thermoelectric Refrigeration and Power Generation
- Graduate Student Researchers: Anastassios Mavrokefalos, Feng Zhou
Sponsor: Office of Naval Research
Period: 06/2004-09/2008 - Compact General-Purpose Bioagent Detector
- Collaboration: Prof. Peter Gascoyne (UT MD Anderson Cancer Center), Prof. Shaochen Chen (UT Austin)
Sponsor: DOD Space and Naval Warfare Center
Period: 07/2003-06/2004 - CAREER: Thermal Transport and Thermoelectric Measurements of Nanotransistors, Nanowires, and Superlattices
- Graduate Student Researchers: Choongho Yu, Jianhua Zhou, Sanjoy Saha, Michael T. Pettes, Jae Hun Seol
Sponsor: National Science Foundation
Period: 03/2003-02/2008 - Micro-flow Cytometers based on Dielectrophoretic Particle Focusing
- Graduate Student Researcher: Choongho Yu
Collaboration: Prof. Peter Gascoyne (UT MD Anderson Cancer Center)
Sponsor: Whitaker Foundation through UT Center for Biomedical Engineering
Period: 09/2002-06/2003 - Acquisition of a Scanning Probe Microscope and a Liquid Helium Cryostat for Nanoscale Thermal Science Research and Education at the University of Texas at Austin
- Collaboration: Profs. Shaochen Chen and Zhen Yao (UT Austin)
Sponsor: National Science Foundation
Period: 06/2002-07/2004
