Session U55: ``Trends" in the APS Publication Physics

Topological order, topological insulators, and the search for the Majorana fermion

In condensed matter physics complex order often emerges from simple interactions. Recent experiments show that topological order, previously seen only in 2D electron systems in high magnetic field, can exist in zero field and even in bulk 3D materials called topological insulators, in which spin-orbit coupling induces the topological order. Topologically ordered phases can support new kinds of emergent particles, such as the Majorana fermion. Current experiments in condensed matter, in both fractional quantum Hall systems and strong spin-orbit materials, are probing the physics of Majorana fermions, which may eventually enable a topological approach to quantum computing.   

Quantum information in solid-state systems

I review the theoretical concepts for spin qubits and scalable quantum computers in nanostructures and highlight the experimental progress in this fast moving field [1]. I describe the standard model of quantum computing and the basic criteria for its potential realization in solid state systems such as GaAs heterostructures, carbon nanotubes, InAs or SiGe nanowires, etc. Other alternative formulations such as measurement-based and adiabatic quantum computing are mentioned briefly. I then focus on qubits formed by individual electron spins in single and double GaAs quantum dots. Introducing the problem of decoherence arising from spin orbit and hyperfine interactions I discuss ways to overcome it, such as state narrowing and nuclear magnetism induced by strong correlations [2]. \\[4pt] [1] R. Zak, B. R\"ohlisberger, S. Chesi, and D. Loss, Rivista del Nuovo Cimento 033, 345 (2010).\\[0pt] [2] B. Braunecker, P. Simon, and D. Loss, Phys. Rev. B 80, 165119 (2009).   

Graphene: Deep physics from the all-surface material

The 2010 Nobel Prize in Physics was awarded to Andre Geim and Kostya Novoselov for their experiments on graphene, a single-atom plane of graphite. I will discuss why graphene has generated such excitement in condensed matter physics. Graphene is different: graphene's electrons mimic massless Dirac Fermions. But graphene is also amazingly tunable: Bandgaps can be generated by nanostructuring. Interactions can be tuned by the surrounding dielectric. Strain generates effective ``pseudomagnetic'' fields up to 300 Tesla. The work function can be tuned over a large range. Such tunability promises that graphene will remain interesting as a laboratory for condensed matter physics.