Speakers: CSLA Physics Faculty Find out about research
opportunities for students in physics
and PIZZA PARTY
Speakers: O. Bernal, R. Jishi, and W. Taylor Find out about research
opportunities for students in physics
Dr. Roger Mong
California Institute of Technology
"The Density Matrix Renormalization Group (DMRG):
Methods and Applications"
Abstract: DMRG is a powerful tool that has been extremely successful at numerically
probing 1D quantum systems, but much of the algorithm and language used is
confusing to the general public. Underlying the success of DMRG is
encoding quantum information via the matrix product states (MPS)
representation of a wavefunction. In this talk, I will describe what an
MPS is, and sketch out the DMRG algorithm, explaining the strengths and
pitfalls of the method. I will briefly present applications of these
tools to spin-2 chains, 1D quantum phase transitions, as well as 2D
quantum Hall effect.
PHYSICS DEPARTMENT OPEN HOUSE
Dr. Michael P. Zaletel
University of California, Berkeley
"Chiral Luttinger Liquids and a Generalized Luttinger's Theorem in Fractional Quantum Hall Edges via Finite-Entanglement Scaling"
Abstract: In this talk I will begin with an introduction to `finite entanglement scaling,' a method for measuring critical exponents by using a scaling analysis in which finite entanglement, rather than finite size, cuts off the critical fluctuations. Finite entanglement scaling can be applied to the gapless edges of the fractional quantum Hall (FQH) effect by using the infinite system density matrix renormalization group (iDMRG) method. I will focus on the hierarchy states, for which we find detailed evidence for the universality of scaling exponents in chiral edges and demonstrate that renormalization is subject to universal relations in the non-chiral case. I will then discuss and prove a generalized version of Luttinger's theorem governing singularities in the density of a Hall droplet.
Jim Garrison Physics Department, University of California, Santa Barbara
"Modeling Strongly Correlated Quantum Phases Using Numerical Methods: Insights and Progress "
The "strange metal" phase of high-temperature superconductors is one
example of a strongly correlated phase of matter which cannot be
effectively described in terms of non-interacting electrons. Although it is
possible to construct simple models which are thought to exhibit the
qualitative physics of these materials, solving such a model is incredibly
difficult. The most straightforward numerical method would be to explicitly
diagonalize the Hamiltonian matrix, but this fails beyond the smallest system
sizes, as the basis size grows exponentially with system size, quickly eclipsing
the available memory on a computer. Fortunately, recent physical insights have
led physicists to develop other (approximate) numerical methods for studying
these systems which work for larger systems. I will describe how a combination
of variation Monte Carlo (VMC) and density-matrix renormalization group (DMRG)
calculations, supplemented with theoretical understanding, can be used to realize
and understand strongly correlated phases on quasi-one-dimensional "ladder" systems.
Ni Ni Department of Physics and Astronomy, University of California, Los Angeles
"Tuning the Ground State of Fe Pnictide Superconductors"
Abstract: Searching for new superconductors and differentiating the key factors impacting Tc are at the core of research in superconductivity. Recently, Fe-based superconductors, the second high temperature superconductor family besides the cuprates, have been discovered to show Tcs up to 55 K. The interplay of the magnetism, superconductivity and structure in Fe-based superconductors makes them a great platform for understanding unconventional superconductivity. In this colloquium, the temperature-dopant concentration (T-x), temperature-extra electrons (T-e), and temperature-pressure (T-P) phase diagrams of the Ba(Fe1-xTMx)2As2 series will be presented. Quantitative analysis of the comparison will be discussed and recent ARPES measurements will be presented to show how electron doping leads to superconductivity in this system. I will also present the effect of doping on the recently discovered, structurally and chemically similar Fe pnictide, Ca10(Pt3As8)(Fe2As2)5 (the “ 10-3-8 phase”) and Ca10(Pt4As8)(Fe2As2)5 (the “ 10-4-8 phase”) compounds and discuss the possible role of metallic spacer layers in this system.