41 research outputs found
Topological Insulators 101
No full textWe thought we knew all there was to know about band insulators back in the 1930s. However, in the last 10 years we have learnt that there distinct types of band insulators in 2 and 3 dimensions. The distinction between these types is topological , a term Dr. Ganpathy Murthy will explain. He will introduce the idea of band topology in detail in 2D. He will then use the example of the integer quantum Hall effects to show that a topological insulator has edge states that are robust to disorder. Next he will introduce time-reversal invariance, which puts powerful constraints on band insulators. Once again, edge modes will prove to be extremely useful in characterizing the different types of band insulators. He will end up by talking about 3D topological insulators and some of the phenomenology associated with them
Disordered SU(<i>N</i>) antiferromagnets and the renormalization of charged instanton gases in three dimensions
No full textBig Bang Theory, Dark Matter and Dark Energy: 2. What’s the Evidence for the Big Bang and Expansion of the Universe? What Do We Measure and How?
No full textWhat’s the evidence? How we know the Big Bang happened, and that the universe is expanding and accelerating. How we measure how fast different parts of the Universe are moving away
Big Bang Theory, Dark Matter and Dark Energy: 1. The Big Picture; the History of the Universe from the Big Bang to Now
No full textThe big picture; the history of the universe from the Big Bang to now. Important scientific milestones leading to our present knowledge
Hall Crystal States at<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="italic">ν</mml:mi><mml:mspace /><mml:mo>=</mml:mo><mml:mspace /><mml:mn>2</mml:mn><mml:mn /></mml:math>and Moderate Landau Level Mixing
No full textBig Bang Theory, Dark Matter and Dark Energy: 3. More Evidence, Including the Evidence for Dark Matter, and Dark Energy
No full textMore on the Big Bang, how we measure how far away different parts of the universe are Dark Matter, Dark Energ
Quantum Hall to Insulator Transition in the Bilayer Quantum Hall Ferromagnet
No full textWe describe a phase transition of the bilayer quantum Hall ferromagnet at . In the presence of static disorder (modeled by a periodic potential), bosonic spinons undergo a superfluid-insulator transition while preserving ferromagnetism. The Mott insulating phase has an emergent photon, and the transition is between Higgs and Coulomb phases of this photon. Consequences for charge and counterflow conductivity and for interlayer tunneling conductance are discussed.PhysicsAuthor's Origina
\u3cem\u3eν\u3c/em\u3e = 1/2 Landau Level: Half-Empty Versus Half-Full
No full textWe show here that an extension of the Hamiltonian theory developed by us over the years furnishes a composite fermion (CF) description of the ν = 1/2 state that is particle-hole (PH) symmetric, has a charge density that obeys the magnetic translation algebra of the lowest Landau level (LLL), and exhibits cherished ideas from highly successful wave functions, such as a neutral quasiparticle with a certain dipole moment related to its momentum. We also a provide an extension away from ν = 1/2, which has the features from ν = 1/2 and implements the PH transformation on the LLL as an antiunitary operator T with T2 = −1. This extension of our past work was inspired by Son, who showed that the CF may be viewed as a Dirac fermion on which the particle-hole transformation of LLL electrons is realized as time-reversal, and Wang and Senthil, who provided a very attractive interpretation of the CF as the bound state of a semion and antisemion of charge ±e/2. Along the way, we also found a representation with all the features listed above except that now T2 = +1. We suspect it corresponds to an emergent charge-conjugation symmetry of the ν = 1 boson problem analyzed by Read
