Nano Energy Group

News


 

Jaykanth's paper in this month's Nature Materials studied the crossover from incoherent to coherent phonon scattering in epitaxial oxide superlattices.
Feb, 2014
Ravichandran, thermal conductivity, oxide superlattice
Elementary particles such as electrons or photons are frequent subjects of wave-nature-driven investigations, unlike collective excitations such as phonons. The demonstration of wave–particle crossover, in terms of macroscopic properties, is crucial to the understanding and application of the wave behaviour of matter. We present an unambiguous demonstration of the theoretically predicted crossover from diffuse (particle-like) to specular (wave-like) phonon scattering in epitaxial oxide superlattices, manifested by a minimum in lattice thermal conductivity as a function of interface density. We do so by synthesizing superlattices of electrically insulating perovskite oxides and systematically varying the interface density, with unit-cell precision, using two different epitaxial growth techniques. These observations open up opportunities for studies on the wave nature of phonons, particularly phonon interference effects, using oxide superlattices as model systems, with extensive applications in thermoelectrics and thermal management.

 

This month's MRS Bulletin featured the plenary address by Dr. Arun Majumdar in the 2013 MRS Spring Meeting.
Nov 26, 2013
MRS Bulletin

The featured article, "A new industrial revolution for a sustainable energy future", is based on an edited transcript of the plenary talk given by Dr. Majumdar on April 3, 2013. This aritcle provides a techno-economic snapshot of the current energy landscape and identifies several research and development opportunities and challenges, especially where they relate to materials science and engineering, to create the foundation for this new industrial revolution.

 

Link: MRS Bulletin 38, 947-954 (2013)
         


 

This month's MRS Bulletin featured the interview with Dr. Arun Majumdar in the Energy Quarterly section.
Jun 20, 2013
MRS Bulletin Energy Quarterly

MRS Bulletin interviewed Dr. Arun Majumdar at the 2013 MRS Spring Meeting, in which he talked about ARPA-E's initiatives in natural gas, grid-level energy storage, biofuels, air conditioning, power electronics, and smart grid.

In this interview, Dr. Majumdar also talked about the key characteristics of innovation in the energy sector, the global energy challenges, and Google's energy investment.

 

Link: MRS Bulletin 38, 418-419 (2013)
         


 

Students in spotlight: congratulations to Kedar and Andy
Apr 2013
Majumdar group reunioin dinner

Kedar Hippalgaonkar was awarded the MRS Graduate Student Silver Award at the Plenary Session of 2013 MRS Spring Meeting.

Andy Zheng participated in the panel "Solar Photovolatics: Going Global" of the 2013 GW Solar Institute Symposium.

 


 

A wonderful evening in San Francisco: the plenary talk and the group reunion dinner.
Apr 3, 2013
Majumdar group reunioin dinner

Dr. Arun Majumdar gave the plenary talk during the 2013 MRS Spring Meeting, titled "A New Industrial Revolution for a Sustainable Energy Future".

About 30 members and alumni of the Majumdar group, who were attending the MRS Spring Meeting, hosted a reunion dinner in downtown San Fran. Prof. Gang Chen, a long-time friend and colleague of Arun, also joined the dinner and celebrated Arun's birthday.

 


 

Dr. Arun Majumdar joined Google.
Dec 17, 2012
Arun Majumdar Joins Google Energy

Energy has been the cornerstone of the world’s increasing prosperity and economic growth since the beginning of the industrial revolution. We need a new energy blueprint for the twenty-frist century, to bring reliable, sustainable and affordable energy to everyone.

In his new role at Google, Dr. Arun Majumdar will focus on energy technology innovation, drive Google.org's energy initiatives and advise on Google's broader energy strategy.

 


 

In a recent presentation of View from the Top lecture series, Dr. Arun Majumdar shared with the Cal Engineering community about "a New Industrial Revolution for a Sustainable Energy Future".
Aug 30, 2012
This talk will provide a techno-economic snapshot of the current energy landscape and discuss several research and development opportunities and challenges to create the foundation for this new industrial revolution. The talk will discuss policies to stimulate innovation and align market forces to accelerate the development and deployment of affordable, accessible and sustainable energy that can simultaneously power economic growth, increase energy security and mitigate the risks of climate change

 


 

In a recent Nature article, Secretary Chu and Dr. Arun Majumdar presented a perspective for a sustainable energy future.
Aug 16, 2012
A sustainable energy future by Steven Chu and Arun Majumdar
Access to clean, affordable and reliable energy has been a cornerstone of the world’s increasing prosperity and economic growth since the beginning of the industrial revolution. Our use of energy in the twenty-first century must also be sustainable. Solar and water-based energy generation, and engineering of microbes to produce biofuels are a few examples of the alternatives. This Perspective puts these opportunities into a larger context by relating them to a number of aspects in the transportation and electricity generation sectors. It also provides a snapshot of the current energy landscape and discusses several research and development opportunities and pathways that could lead to a prosperous, sustainable and secure energy future for the world.

 

In a recent interview by the New York Times' blog "Green", Dr. Arun Majumdar gave a panoramic view of energy innovation.
Jun 11, 2012
Arun Majumdar New York Times interview
Dr. Arun Majumdar took a sharp look at why ARPA-E is needed, its breakthroughs, and the benefits even when things don’t go well. “Industrial revolutions don’t happen overnight. They’re built brick by brick,” Majumdar said. “In the energy sector, it takes sometimes a decade or more for new technologies to flourish,” adding, “There is no holy grail, no silver bullet.” He described his time in Washington as a “wonderful education,” hard to get any other way.

 


 

In collaboration with Peidong Yang's group in the Chemistry department, Kedar's recent paper in Nano Letters featured a quantitative study of the effect of surface roughness on the thermal conductivity of Silicon nanowires.
Apr, 2012
Kedar Nano Letters surface roughness
Although it has been qualitatively demonstrated that surface roughness can reduce the thermal conductivity of crystalline Si nanowires (SiNWs), the underlying reasons remain unknown and warrant quantitative studies and analysis. In this work, vapor–liquid–solid (VLS) grown SiNWs were controllably roughened and then thoroughly characterized with transmission electron microscopy to obtain detailed surface profiles. Once the roughness information (root-mean-square, σ, correlation length, L, and power spectra) was extracted from the surface profile of a specific SiNW, the thermal conductivity of the same SiNW was measured. The thermal conductivity correlated well with the power spectra of surface roughness, which varies as a power law in the 1–100 nm length scale range. These results suggest a new realm of phonon scattering from rough interfaces, which restricts phonon transport below the Casimir limit. Insights gained from this study can help develop a more concrete theoretical understanding of phonon–surface roughness interactions as well as aid the design of next generation thermoelectric devices.

 

In the 2012 ARPA-E energy innovation summit, Dr. Arun Majumdar gave a keynote presentation on the ARPA-E's role in meeting the 21st century's energy challenges with American innovation.
Feb 28, 2012
Dr. Arun Majumdar, the director of DOE’s ARPA-E, gave a keynote presentation about the 21st century's energy challenges for sustainable national development, and described ARPA-E's efforts, as part of the American innovation, to meet these challenges in biofuel, electrofuel, batteries for electric cars, clean coal, carbon capture, grid-scale energy storage for renewables, electrical infrastructure, and etc.