Massive Dirac Fermions and Hofstadter Butterfly in a van der Waals Heterostructure

  • By Aude Marjolin
  • 21 June 2013

The remarkable transport properties of graphene, such as the high electron mobility, make it a promising material for electronics. However, unlike semiconductors such as silicon, graphene's electronic structure lacks a band gap, and a transistor made out of graphene would not have an “off” state. Ben Hunt and his colleagues modulated the electronic properties of graphene by building a heterostructure consisting of a graphene flake resting on hexagonal boron nitride (hBN), which has the same honeycomb structure as graphene, but consists of alternating boron and nitrogen atoms instead of carbons. The natural mismatch between the graphene and hBN lattices led to a moire pattern with a large wavelength, causing the opening of a band gap, the formation of an elusive fractional quantum Hall state, and, at high magnetic fields, a fractal phenomenon in the electronic structure called the Hofstadter butterfly.

Quantum-Engineered Nanoscale Alloys So Bright They Could Have Potential Medical Applications

  • By Aude Marjolin
  • 14 May 2013

Alloys like bronze and steel have been transformational for centuries, yielding top-of-the-line machines necessary for industry. As scientists move toward nanotechnology, however, the focus has shifted toward creating alloys at the nanometer scale—producing materials with properties unlike their predecessors.

Now, researchers led by PQI faculty Jill Millstone demonstrate that nanometer-scale alloys possess the ability to emit light so bright they could have potential applications in medicine. The findings have been published in the Journal of the American Chemical Society.

Connecting the (Quantum) Dots: Spin Technique Moves Researchers Closer to Creating First Viable High-Speed Quantum Computer

  • By Aude Marjolin
  • 26 February 2013

Recent research offers a new spin on using nanoscale semiconductor structures to build faster computers and electronics. Literally.

Researchers at PQI and Delft University of Technology reveal in the Nature Nanotechnology a new method that better preserves the units necessary to power lightning-fast electronics, known as qubits (pronounced CUE-bits). Hole spins, rather than electron spins, can keep quantum bits in the same physical state up to 10 times longer than before, the report finds.


Theoretical Chemistry Research Looks to Reduce Side Effects of Medications for Depression, Addiction, Disease

  • By Aude Marjolin
  • 14 February 2013

A research team including PQI faculty Dr. Jeffry D. Madura is attempting to unravel the regulation of dopamine, which leads to happiness. By mapping how these critical neurotransmitters are controlled, Madura and colleagues are trying to better understand the function and structure of the proteins that modulate the receptor/transporter processes of dopamine and serotonin as well as amphetamines and cocaine. The group already has identified a compound as a potential new class of serotonin inhibitors, which would work with the proteins that transport the hormone.

Their initial findings were reported in the Biophysical Journal, with their detailed analysis expected to be published soon.

Nanoscientists Suggest Use of Vacuums to Overcome Limits of Conventional Silicon-Based Semiconductor Electronics

  • By Aude Marjolin
  • 2 July 2012

With the advent of semiconductor transistors—invented in 1947 as a replacement for bulky and inefficient vacuum tubes—has come the consistent demand for faster, more energy-efficient technologies. To fill this need, researchers at PQI are proposing a new spin on an old method: a switch from the use of silicon electronics back to vacuums as a medium for electron transport—exhibiting a significant paradigm shift in electronics. Their findings were published in Nature Nanotechnology.

"Physical barriers are blocking scientists from achieving more efficient electronics," said Hong Koo Kim, PQI faculty and principal investigator on the project. "We worked toward solving that road block by investigating transistors and its predecessor—the vacuum."

PQI Team Awarded Grant to Simulate Turbulent Combustion in Aerospace Applications

  • By Aude Marjolin
  • 18 April 2012

A research team at PQI is developing quantum-computing algorithms to better model turbulent combustion in aerospace applications. A five-year U.S. Air Force grant was awarded this month to principal investigator and PQI faculty Peyman Givi, Andrew Daley, and Jeremy Levy.

"If some of the things we are thinking do work and eventually we do achieve this, a process that could take weeks or months will transpire in minutes," said Givi. "It really is a quantum leap."