Paving the Way Towards 1D Helical Conductors with Fractional Quantum Statistics

  • By Aude Marjolin
  • 22 February 2017

In a letter published in the February 2017 issue of Nature Nanotechnology, Ben Hunt and his collaborators at the Massachusetts Institute of Technology, the University of California Santa Barbara, and the National Institute for Materials Science in Tsukuba, Japan describe how they engineered a graphene electron–hole bilayer device into a helical 1-dimensional (1D) conductor and characterized its transport properties. In a helical 1D conductor, electrons moving in opposite directions also have opposite spin polarizations, and such helical states can be obtained by combining two quantum Hall (QH) edge states with opposite spins and opposite momenta relative to the magnetic field (i.e. opposite chiralities).

My colleagues at MIT came up with this ingenious way of producing helical edge states from two decoupled graphene layers, and then they proved their idea worked with a series of powerful transport experiments,” says Hunt. “I was thrilled to be able to make a contribution to the experiment by using capacitance measurements to help prove that the unique helical states they observe really are edge states.”

Sergey Frolov Among 2017 Young Investigator Award Recipients

  • By Aude Marjolin
  • 22 February 2017

The Office of Naval Research has announced awards of $16 million through its 2017 Young Investigator Program (YIP). The awards were made to 33 scientists whose research holds strong promise across several naval-relevant science and technology areas.

Sergey Frolov was among this year's Young Investigator Award recipients for his proposal "Semiconductor Nanowire-Based Quantum Emulators".

Lillian Chong Receives 2017 Tina and David Bellet Teaching Excellence Award

  • By Aude Marjolin
  • 22 February 2017

Established in 1998 with a gift from Dietrich School alumnus, David Bellet (A&S '67) and his wife Tina, and endowed in 2008 through the family's further generosity, this annual award recognizes outstanding and innovative teaching in undergraduate studies in the Kenneth P. Dietrich School of Arts and Sciences.

Sean Garrett-Roe Awarded Chancellor’s Distinguished Teaching Award

  • By Aude Marjolin
  • 15 February 2017

Sean Garrett-Roe has been selected to receive a 2017 Chancellor's Distinguished Teaching Award. The Chancellor's Distinguished Teaching Award recognizes teaching excellence by members of the University of Pittsburgh's faculty. This award consists of a cash prize to the faculty member and a grant to support the faculty member's teaching activities. 

Garrett-Roe was recognized for his work with the Process Oriented Guided Inquiry Learning (POGIL) approach, which uses a flipped classroom model, multisensory input and incorporates technologies to encourage students to engage, derive and interpret the materials of physical chemistry. He has also shared his pedagogical models in such venues as Pitt’s Summer Instructional Design Institute and the American Chemical Society’s national meeting.

PQI Members Receive 2016 Kaufman Awards

  • By Aude Marjolin
  • 8 February 2017

In this fourth year of the annual competition, a total of eight grants were awarded to researchers at four Pennsylvania higher education institutions: Carnegie Mellon University, the University of Pittsburgh, The Pennsylvania State University and University of Pennsylvania.

The Kaufman Scientific Advisory Board received 229 letters of intent from 30 academic institutions seeking funding in two categories: New Investigators and New Initiatives.

Benjamin Hunt won a New Investigators Award, i.e., a grant of $150,000 for two years ($75,000 per year), for research on “Proximity effects and topological spin currents in van der Waals heterostructures.” 

Brian D’Urso and Gurudev Dutt won a New Initiatives Award, i.e., a grant of $300,000 for two years ($150,000 per year) for research on “Trapped diamond nanocrystals for precision gravitational measurements and tests of quantum gravity.” 

Read the abstracts here and here, respectively.

Hrvoje Petek Writes a News and Views Article in Nature Nanotechnology

  • By Aude Marjolin
  • 10 January 2017

Photovoltaics in action: Electron motion in a type-II InSe/GaAs semiconductor heterostructure has been recorded in a movie immediately after photoexcitation with high spatial and temporal resolution.

Electrons are the lifeblood of semiconductor devices, from transistors that power computers and smart phones, and semiconductor diodes that light up the night, to photovoltaic cells that harvest solar energy to power it all. Under the influence of applied voltages or light stimulations, electrons flow through nanoscale channels and plummet potential gradients at interfaces of disparate materials. In a semiconductor device this ebb and flow occurs several times every nanosecond within billions of transistors on a single microchip, unseen by human eye, but creating text, images and movies in strings of 0s and 1s. But the true time and spatial scales on which electrons are energized and transported span a range of hundreds of femtoseconds and tens of nanometres. Thus, to capture in a movie the physical phenomena of electrons in a device requires a truly extraordinary camera. Writing in Nature Nanotechnology, Man et al. report an experiment that performs just that. Specifically, they record a movie of electron flow in energy, space and time within a semiconductor heterojunction composed of GaAs in physical contact with InSe by imaging electrons emitted into vacuum through the joint action of femtosecond duration IR generation and UV electron emission laser pulses.

David Snoke's PRL Article Highlighted in Physics Viewpoint

  • By Aude Marjolin
  • 9 January 2017

Matter-Light Condensates Reach Thermal Equilibrium

Making use of improved microcavities, hybrid condensates of matter and light can be tuned to reach a thermal equilibrium state, despite their finite lifetime.

In a laser, coherent light is created by stimulated emission of photons from an “inverted” state of matter that is significantly out of thermal equilibrium. “Inverted” means that excited states of the matter are more occupied than lower energy states, so that emission is more likely than absorption. The coherence of laser light is closely related to a quite different, and less commonly encountered, state of matter—a Bose-Einstein condensate (BEC). In the textbook description of a BEC, at low enough temperatures or high enough densities, a large number of particles occupy the same state, producing a coherent state of matter. In contrast to laser light, the textbook BEC is in thermal equilibrium. Condensates of polaritons—half-light, half-matter quasiparticles—have so far been found in conditions halfway between those of an equilibrium BEC and those of a laser. Work by David Snoke and colleagues now shows that such polariton condensates can be tuned to reach a thermal equilibrium state. With this tunability between an equilibrium and nonequilibrium state, researchers can explore how the character of phase transitions evolves between the two limits.

Peng Liu receives CAREER Award

  • By Aude Marjolin
  • 16 December 2016

Peng Liu has been selected to receive a National Science Foundation CAREER award based upon his proposal, entitled "Computational Studies of Transition-Metal-Catalyzed Reactions in Organic Synthesis." 

In this CAREER project funded by the Chemical Structure, Dynamic & Mechanism B Program of the Chemistry Division, Professor Peng Liu of the Department of Chemistry at the University of Pittsburgh is developing new strategies to use computational tools to investigate mechanisms and effects of ancillary ligands in transition-metal-catalyzed reactions of unactivated starting materials, such as C-C and C-H bonds, and unactivated olefins. The goal of this research is to reveal the fundamental reactivity rules of common organometallic intermediates in these transformations and to develop new models to interpret ligand effects on reactivity and selectivity. This proposal’s educational and outreach plan aims to maximize the power of computations to enhance learning of organic chemistry concepts and to facilitate synthetic organic chemistry research. Professor Liu’s team will develop virtual reality (VR) software and educational materials to visualize three-dimensional molecular structures and reaction mechanism videos in an interactive and immersive environment.