Spring 2018

Innovative and Novel Computational Impact on Theory and Experiment (INCITE) Program

  • By Burcu Ozden
  • 1 May 2018

The Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program promotes transformational advances in science and technology for computationally and/or data intensive, large-scale researchprojects through large allocations of computer time and supporting resources at the Argonne and Oak Ridge Leadership Computing Facility (LCF) centers, operated by the US Department of Energy (DOE) Office of Science. INCITE seeks research enterprises for capability computing: production simulations, data science, and/or learning applications - including ensembles - that use a large fraction of the LCF systems or require the unique LCF architectural infrastructure for high-impact projects that cannot be performed on less capable resources. 

INCITE is currently soliciting proposals of research for awards on LCF HPC machines for calendar year (CY) 2019. LCF HPC machines include Summit, the 200-petaflop IBM 922AC machine; Titan, the 27-petaflop Cray XK7; Mira, the 10-petaflop IBM Blue Gene/Q; and Theta, the 12-petaflop Cray XC40 machine. Fifty percent of the allocable computing time will be made available on each of these machines to the INCITE program. 

Open system approaches for quantum transport through tunneling junctions

François Damanet
Thursday, April 26, 2018 - 4:00pm

Quantum transport is a key area in quantum physics which presents challenges in terms of theoretical description. In this talk, I will present how the non-equilibrium dynamics of tunneling junctions weakly coupled to baths of fermionic or bosonic particles can be investigated using open system approaches, namely input-output formalisms and master equations. As a specific example, I will first present our study of electron transport in a quantum dot tunneling junction connecting two normal or superconducting leads, where both single-particle and Cooper-pair tunneling are considered. In particular, I will show how signatures of Andreev bound states can be obtained in the output currents. Then, I will present our results on spin transport in a quadratic spin system connecting baths modeled as XXZ spin chains. Based on non-Markovian master equations for the system and t-Matrix Product States simulations to compute the bath correlation functions, we showed that the spin current through the system can be enhanced due to the presence of the interaction in the baths as well as exhibit transient rectification (i.e. different current under bias exchange). Finally, I will sketch a more general outlook on how non-Markovian master equations could be used to study the transport properties of a system of unknown spectrum, which is particularly useful for the case of complicated time-dependent or many-body system Hamiltonians.

Computational Chemical Sciences Research

  • By Burcu Ozden
  • 24 April 2018

The DOE SC program in Basic Energy Sciences (BES) announces its interest in receiving applications from single principal investigators (PIs), small groups (2-3 PIs), and centers (integrated multidisciplinary teams typically from multiple institutions) in Computational Chemical Sciences (CCS). CCS will support efforts to develop validated, public access codes and databases, and research to develop new approaches to enhance the use of large data sets for deriving new fundamental knowledge from calculations and advanced characterization of chemical systems. CCS will continue to support the DOE Exascale Computing Initiative (ECI), which was announced in September 2013. The ECI aims to accelerate the research and development needed to overcome key exascale challenges and maximize benefits of high-performance computing. This FOA continues the BES commitment to ECI by developing open source codes that can take full advantage of today's petascale and future exascale leadership computing facilities.

Accelerating Your Research with No-Cost Resources for Computing, AI, and Data with PSC

Nick Nystrom
Wednesday, May 9, 2018 - 3:30pm to 4:30pm

Pittsburgh Supercomputing Center (PSC) offers powerful resources for computing, artificial intelligence, and data management and analytics that are available at no charge for open research and to support coursework. In this talk, we will survey examples of breakthroughs that are using PSC resources and ways to leverage PSC for your own research. Examples will highlight successes in genomics, AI, neuroscience, engineering, and other fields. We will highlight two PSC resources that provide unique capabilities: Bridges and Anton 2. Bridges converges high-performance computing (HPC), artificial intelligence (AI), and Big Data and offers a familiar, an exceptionally flexible user environment, applicable to whatever data analytics or simulation exceed groups’ local capabilities. Anton 2 is a special-purpose computer that dramatically increases the speed of molecular dynamics (MD) simulations to understand the motions and interactions of proteins and other biologically important molecules over much longer time periods than would otherwise be accessible. We will also describe Compass AI, a new initiative to help the community make the most of emerging hardware and software technologies for AI, develop best practices, provide education and training, and establish collaborations, especially between academia and the private sector. We outline areas of expertise at PSC where we are conducting research and open to additional collaboration. We close with a summary of opportunities to co-locate computational resources at PSC, with possible benefits of saving money, bursting to larger resources when needed, and leveraging PSC’s broad software collection. 

A number of PSC’s scientific staff will be present for discussion at the reception following the seminar. A reception will follow at 4:30pm

Two Dimensional Quantum Materials - An Atomically Thin Platform for Spintronics and Novel Spin Phenomena 

Simranjeet Singh
Tuesday, May 1, 2018 - 4:30pm to 5:30pm

Two dimensional (2D) quantum materials provide a versatile experimental platform to probe spin-dependent novel quantum phenomena emerging at the nanoscale. The possibility of on-demand tuning of spin properties of 2D materials by external knobs such as electric field, substrate engineered proximity, etc., can have far-reaching implications for spintronics. I will discuss our experiments demonstrating a strong modulation of spin currents in bilayer graphene using static and fluctuating proximity exchange fields of a ferromagnetic insulator (FMI). We achieve complete spin modulation in graphene layers by controlling the direction of the exchange field of a nearby magnetic material in graphene/FMI heterostructures. A strong magnetic exchange coupling across the interface in graphene/FMI heterostructures leads to the experimental observation of full spin modulation at low externally applied magnetic fields in mesoscopic graphene spin channels. In graphene/FMI heterostructures, we also discover a novel spin dephasing mechanism due to randomly fluctuating magnetic exchange fields. This is manifested as an unusually strong temperature dependence of the non-local spin signals in graphene, which is due to spin relaxation by thermally-induced transverse fluctuations of the FMI magnetization. 

In the second half of my talk, I will discuss spin-charge interconversion driven by the Rashba effect in van der Waal bonded platinum/graphene (Pt/Gr) heterostructures. The interfacial spin-orbit interaction driven Rashba effect in low-dimensional systems can enable efficient and tunable spin-charge interconversion for spintronics applications. I will show that an applied electric field at the Pt/Gr Rashba interface results in a net spin accumulation in graphene, with spin polarization quantized along a direction transverse to the applied electric field. This current induced non-zero spin accumulation at the Pt/Gr interface is a direct consequence of uncompensated spin-textured Femi surfaces of the graphene Dirac states due to a symmetry-breaking electric field normal to the Pt/Gr heterostructure. Employing the Pt/Gr Rashba interface, we also realize the first experimental demonstration of the Onsager reciprocity between charge and spin via Rashba Edelstein effect (REE) and inverse-REE. This work is a significant advancement in graphene spintronics and provides an alternative experimental approach to generating and detecting spins using extrinsically tunable interfacial spin-orbit phenomena in two-dimensional materials.

Gurjyot Sing Sethi Won the 1st Place in the Annual CMU Energy Week Poster and Multimedia Competition

  • By Burcu Ozden
  • 17 April 2018

The CMU Energy Week Poster and Multimedia Competition is a unique opportunity to showcase your energy-related research and other activities, such as software, videos, art, models or sculptures. Participants will be able to submit either Science, Technology, Engineering and Mathematics (STEM) related or Non-STEM related work. 

The competition was open to Carnegie Mellon undergraduate, master's and PhD students and postdoctoral researchers. 

Gurjyot Sing Sethi won the 1st place in this competition with his poster titled "Identifying the prospects of Electrochemical Ammonia Synthesis using First-Principles Calculations."

He was awarded $1,000.

Gurjyot Sing Sethi is a graduate student in Venkat Viswanathan's group.

Venkat Viswanathan Quoted About Lithium-Air Batteries in Chemistry World

  • By Burcu Ozden
  • 17 April 2018

Chemistry World quoted Venkat Viswanathan on the cycle life of lithium-air batteries. These batteries hold a charge greater by a factor of nine compared to lithium-ion. In interpreting the batteries’ cycle life, Viswanathan expresses a distanced view. A traditional lithium-ion battery’s life is measured by its electrical discharge. In a lithium-air battery, discharge from the reaction of lithium and oxygen determines cycle life. But because air comprises more elements than just oxygen, Viswanathan wonders how many side reactions in the electricity delivery artificially boost the cycle life. Mitigating these side reactions should pave the way to developing long-lasting lithium-air batteries.

Research at the Frontiers of X-Ray Free Electron Laser Ultrafast Chemical and Materials Sciences

  • By Burcu Ozden
  • 17 April 2018

The Office of Basic Energy Sciences (BES), U.S. Department of Energy (DOE), announces its interest in receiving applications from small groups of investigators for support of experimental and theoretical efforts to advance ultrafast chemical and materials sciences that utilize x-ray free electron lasers