Harvard University Department of Physics

Sending Spin Waves into an Insulating 2D Magnet

Quantum Hall ferromagnets are among the purest magnets in the world — and one of the most difficult to study. These 2D magnets can only be made in temperatures less than a degree above absolute zero...

Origin of Mott Insulating Behavior and Superconductivity in Twisted Bilayer Graphene

A new theory describes how both insulating and superconducting behavior arises from sheets of graphene stacked and twisted at a particular "magic" angle.

Physical Interpretation of the Partition Function for Colloidal Clusters

Colloidal clusters consist of small numbers of colloidal particles bound by weak short-range attractions. The equilibrium probability of observing a cluster in a particular geometry is well described by a statistical mechanical model originally developed for molecules...

UPCOMING EVENTS

Today

Fikile Brushett - MIT
Start: 06:00pm - End: 07:30pm
- 06:00pm
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Tomorrow

CMP Seminar: Jason Alicea (Caltech), hosted by Ashvin Vishwanath
Start: 12:00pm - End: 01:00pm
- Title: Electrical probes of the non-Abelian spin liquid phase in \alpha-RuCl3
  
  Abstract: Recent thermal-transport experiments indicate that the Kitaev material RuCl_3 realizes a non-Abelian spin liquid with Ising topological order over a range of magnetic fields. This talk will explore a series of measurements for electrically detecting the hallmark chiral Majorana edge states and bulk anyons in the spin-liquid phase -- despite the fact that RuCl_3 is a good Mott insulator. In particular, I will introduce circuits that exploit interfaces between electronic systems and RuCl_3 to convert physical fermions into emergent fermions, thus enabling analogues of transport probes of non-Abelian-anyon physics in topological superconductors. I will further propose detection of individual bulk neutral fermions via a spin counterpart of charge sensing. These results illuminate a partial pathway towards using Kitaev materials for topological quantum computation.
- 12:00pm
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ITAMP Lunch Seminar
Start: 12:00pm - End: 01:00pm
- Speaker: Robert Bettles
- 12:00pm
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Monday, November 19th

Professor Aharon Kapitulnik, Stanford University
Start: 04:15pm - End: 05:15pm
- Transport in Strongly Correlated Bad Metals
  
  The Boltzmann-Drude picture of electronic transport with well defined quasiparticle excitations breaks down when the electron mean-free-path becomes of order of the Fermi wavelength. Beyond this so-called Mott-Ioffe-Regel (MIR) limit, metallic behavior becomes incoherent, and materials that continue to exhibit resistance that increases with temperature without saturation above that limit are dubbed "bad metals." While there is no unique theory to date to describe such materials, the anomalous transport and strongly interacting nature of these systems suggest a possible relevance to quantum chaos. In this talk we show high-resolution thermal and charge transport data on several strongly correlated complex oxides above the MIR limit. Analyzing the data, we show that both, electrons and phonons carry heat in an overdamped diffusion process, which is characterized by a relaxation time bound and a unique velocity vB which is larger than the sound velocity and smaller than the Fermi velocity. We further discuss the connection between these results and a quantum chaotic system, emphasizing the importance of phonons, and the difference between charge and thermal transport.
- 04:15pm
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Wednesday, November 21st

No Squishy Physics - Happy Thanks Giving
Start: 06:00pm - End: 07:30pm
- 06:00pm
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Monday, November 26th

Professor Matthew Reece, Harvard University
Start: 04:15pm - End: 05:15pm
- “Fundamental Physics from Underground to the Sky”
  
  The Large Hadron Collider’s discovery of the Higgs boson has only sharpened some of the biggest puzzles in fundamental physics. Why is gravity so dramatically weak compared to the other fundamental forces of nature? What is the dark matter that is far more prevalent in our universe than normal matter? Finding the answers to such questions is likely to require us to sharpen our theoretical tools and to study experimental signals from cosmology and astrophysics that lie far afield from traditional particle experiment. I will highlight some recent research aiming to strengthen connections among particle physics, astrophysics, and cosmology.
- 04:15pm
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