Harvard University Department of Physics

R.I.P. Professor Nicolaas Bloembergen

Nicolaas (Nico) Bloembergen, Gerhard Gade University Professor, Emeritus, and 1981 Nobel Laureate, passed away at his home in Tucson, Arizona, on September 5, 2017.

Mach-Zehnder Interferometry Using Spin- and Valley-Polarized Quantum Hall Edge States in Graphene

Confined to a two-dimensional plane, electrons in a strong magnetic field travel along the edge in one-dimensional quantum Hall channels that are protected against backscattering. These channels can be used as solid-state analogs of monochromatic beams of light...

Particle-Hole Symmetry in Descriptions of a Half-Filled Landau Level

Multiple descriptions of the half-filled Landau level, an exotic phase of matter seen in two-dimensional electron gases, have led to incompatible pictures that are widely believed to represent two distinct phases of matter. A new analysis suggests...

UPCOMING EVENTS

Thursday, September 21st

CMP Seminar: Carlos Bolech (Univ. Cincinnati), hosted by Eugene Demler
Start: 12:00pm - End: 01:00pm
- 12:00pm
- Title: "Bosonization and the description of sharply localized states in the continuum"
  
  Abstract: In this talk, we will critically reexamine the bosonization-debosonization procedure for systems including localized features or boundaries. First, by focusing on the case of a tunneling junction out of equilibrium, we will show that the conventional bosonization approach can give results that are not consistent with a direct solution of the problem even at the qualitative level, thus highlighting possible inconsistencies that can adversely affect the results of all types of calculations. We will subsequently report on a "consistent bosonization-debosonization" procedure that we have developed to resolve the aforementioned non-equilibrium transport puzzle and argue that it should be widely applicable [1]. This new framework takes the form of additional considerations, related to the regularization of fermionic bilinears, that supplement the conventional bosonization procedure and it can be carried over to the study of other systems. We will then discuss its application to the two-lead Kondo junction [2], that besides being a key theoretical prototype of a non-equilibrium strongly correlated system is also of continuing experimental relevance. The discussion will be focused on the Toulouse limit of that problem.
  
  [1] N. Shah and C. J. Bolech, Phys. Rev. B 93, 085440 (2016)
  [2] C. J. Bolech and N. Shah, Phys. Rev. B 93, 085441 (2016)
- View in Google Calendar

Friday, September 22nd

CMP Special Seminar: Philipp Stegmann, hosted by Eugene Demler
Start: 11:00am - End: 12:00pm
- 11:00am
- TBA
- View in Google Calendar

Monday, September 25th

Monday Colloquium: Achim Rosch (University of Cologne), title TBA
Start: 04:15pm - End: 05:30pm
- 04:15pm
- View in Google Calendar

Tuesday, September 26th

CMP Special Seminar: Achim Rosch (U. of Cologne)
Start: 01:15pm - End: 02:15pm
- 01:15pm
- Title: Whirls in magnets: from skyrmions to magnetic monopoles
  
  Abstract: Weak perturbations can drive an interacting many-particle system far from its initial equilibrium state if one is able to pump into degrees of freedom approximately protected by conservation laws. This concept has for example been used to realize Bose–Einstein condensates of photons, magnons and excitons. Integrable quantum systems, like the one-dimensional Heisenberg model, are characterized by an infinite set of conservation laws. Here, we develop a theory of weakly driven integrable systems and show that pumping can induce large spin or heat currents even in the presence of integrability breaking perturbations, since it activates local and quasi-local approximate conserved quantities. The resulting steady state is qualitatively captured by a truncated generalized Gibbs ensemble with Lagrange parameters that depend on the structure but not on the overall amplitude of perturbations nor the initial state. We suggest to use spin-chain materials driven by terahertz radiation to realize integrability-based spin and heat pumps.
- View in Google Calendar

Wednesday, September 27th

Xingbo Yang; Needleman group - Harvard University
Start: 05:30pm - End: 07:00pm
- 05:30pm
- View in Google Calendar