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General information
Please RSVP here
if you intend to come so we have an idea how many need lunch/coffee/parking
(last minute decisions to attend are still accepted).
Venue: The meeting will take place in the new Hall of Science (HSCI) room 102.
Access: Information on the access to campus can be obtained here.
Campus map: A map of the campus can be found here.
Parking: You can obtain a parking permit from the Visitor Information Booth (open until 2pm only!) located at the main entrance of campus,
on Beach Drive, entering from Bellflower Blvd. Parking lots 5, 4, 6 and 18 should be used in order of
preference. But beware that the first two may be full. It takes 5min walk from lots 5 and 4, and 7-10 min from lots 6 and 18. Also,
if you arrive after 2pm you will need to purchase a parking permit at a yellow booth for example on lots 17 or 1,2,3.
Lunch: Will be served at the site of the meeting from 12pm to 1pm. Coffee breaks will be at the site of the meeting as well.
Dinner: We will go to a restaurant nearby after the meeting (Diner pays his/her own meal).
The department of Physics & Astronomy at CSU Long Beach: Information can be found
on our
website http://www.csulb.edu/depts/physics
Organization: Andreas Bill (CSULB), Stephan Haas (USC), Michael Peterson (CSULB)
Organizing Committee: Y. Tserkovnyak (UCLA), A. Chernyshev (UCI), K. Shtengel/V. Ajik (UCR),
G. Rafael/J.Alicea (Caltech), D.Arovas (UCSD), N. Kioussis/D. Sheng (CSUN), E. Rezay/JP.Rodriguez (CSULA),
I.Tifrea (CSUF), A. Small (CalPoly Pomona)
Abstracts
Recent developments in spin liquids: DMRG prospective (S. White)
A quantum spin liquid is a solid whose atoms have magnetic moments but,
because of quantum fluctuations, these moments fluctuate like a liquid
even at zero temperature. Two dimensional spin liquids have been suggested as
a way to produce high temperature superconductivity, and to build quantum
computers. Just as helium is the only element which is a liquid at zero
temperature, 2D spin liquids have been extremely difficult to find, despite
decades of effort, raising the question, do realistic spin liquids even exist?
Recently, apparent spin liquids have been found experimentally, stimulating
theoretical work to find simple model Hamiltonians of frustrated spin systems
that have spin liquid ground states.
In this talk, I will give a broad overview of spin liquids and
then focus on our simulations of the kagome Heisenberg model, a simple,
realistic model of some of the recent experimental spin liquids,
where we find a spin liquid ground state.
Ettingshausen effect due to Majorana modes (C.Y. Hou)
The presence of Majorana zero-energy modes at vortex cores in a topological superconductor implies
that each vortex carries an extra entropy s0, given by (kB/2) ln 2, that is independent of temperature.
By utilizing this special property of Majorana modes, the edges of a topological superconductor can be
cooled (or heated) by the motion of the vortices across the edges. As vortices flow in the transverse
direction with respect to an external imposed supercurrent, due to the Lorentz force, a thermoelectric
effect analogous to the Ettingshausen effect is expected to occur. We propose an experiment to observe
this thermoelectric effect, which could directly probe the intrinsic entropy of Majorana zero-energy modes.
Iron-pnictide High-Tc Superconductivity from the limit of Local Magnetic Moments (J. Rodriguez)
We analyze a two-orbital t-J model over a square lattice of iron atoms by Schwinger-boson-slave-fermion
mean-field theory and by exact diagonalization on a 4x4x2-site cluster. The low-energy spectrum of
one hole exhibits electronic structure at 2D momenta (0,0) , (pi,0) and (0,pi) for Hund's Rule coupling
near a critical value of moderate strength. Increasing Hund's Rule coupling off the critical point can
lead to the absence of the Fermi-surface pockets centered at momentum (0,0). This effect potentially
accounts for the same behavior observed recently in single-layer iron-selenide superconductors, which
exhibit a record Tc of 65 K. Mean-field theory further predicts s-wave Cooper pairs that alternate
in sign between hole momenta at (0,0) and at (pi,0). Exact diagonalization of two holes confirms this,
and it also finds an orbital-singlet/spin-triplet s-wave state close by in energy.
Fractional topological insulators: the role of band geometry (R. Roy)
Recent numerical simulations of flat band models with interactions which show clear evidence of
fractionalized topological phases in the absence of a net magnetic field have generated a great deal
of interest. We provide an explanation for these observations by showing that the physics of these
systems is the same as that of conventional fractional quantum Hall phases in the lowest Landau level
under certain ideal conditions which can be specified in terms of the Berry curvature and the Fubini
study metric of the topological band. In particular, we show that when these ideal conditions hold,
the density operators projected to the topological band obey the celebrated W∞ algebra. Our approach
provides a quantitative way of testing the suitability of topological bands for hosting fractionalized
phases.
Fractional quantum Hall effect in graphene: effects of Landau level mixing (M. Peterson)
We study the effects of Landau level mixing on the fractional quantum Hall effect in graphene.
Landau level mixing in graphene is especially important since the ratio of the Coulomb energy to the
cyclotron energy is independent of magnetic field and of order one. We derive an effective Hamiltonian
that fully incorporates Landau level mixing by renormalizing the two-body Coulomb potential (renormalizing
the Haldane pseudopotentials) and inducing particle-hole symmetry breaking three-body terms, cf. Bishara and
Nayak, Phys. Rev. B 80, 121302(R) (2009). As opposed to the FQHE in GaAs semiconductor devices, graphene
has no finite-thickness corrections since the two-dimensional graphene sheet is atomically thin and
the Dirac nature of the electrons in graphene forces the particle-hole symmetry breaking three-body
terms to exactly vanish in the lowest Landau level.
We acknowledge support from DARPA, Microsoft Station Q, and Cal State Long Beach Start-up.
Topological Quantum Engineering: Constructing exotic phases from known states of matter (D. Clarke)
Non-Abelian anyons are widely sought for quantum computing applications as
well as for the fundamental physics they harbor. As systems
containing such excitations are not easily come by in nature, I have been
engaged in efforts to produce these extraordinary objects by judiciously
interfacing more well-understood phenomena, such as superconductors and
fractional quantum Hall states. There are now many blueprints for
stabilizing the simplest type of non-Abelian anyon, Majorana zero modes.
Here, I will introduce an experimentally feasible device in which defects
bind zero energy operators with more general parafermionic commutation
relations. These parafermionic defects take us an important step closer to
universal quantum computation, and demonstrate the power of the
'engineering' approach in the search for non-Abelian anyons.
Fluctuation theorems for quantum processes (T. Albash)
We present fluctuation theorems and moment generating function equalities for generalized thermodynamic
observables and quantum dynamics described by completely positive trace preserving (CPTP) maps. Our
results include the quantum Jarzynski equality and Crooks fluctuation theorem, and clarify the special
role played by the thermodynamic work and thermal equilibrium states in previous studies. We show that
for a specific class of generalized measurements, which include projective measurements, unitality
replaces micro-reversibility as the condition for the physicality of the reverse process in our fluctuation
theorems. We present an experimental application of our theory to the problem of extracting the system-bath
coupling magnitude, which we do for a system of pairs of coupled superconducting flux qubits undergoing
quantum annealing.
Fractional Chern Insulator and its Modular Matrix (D. Sheng)
Energy band theory provides successful understanding of the metal and insulator behaviors of solids
when electrons are not strongly interacting. Interestingly, a band insulator can be a topological insulator (TI),
which is distinguishable from an ordinary insulator by the topological invariant of the system.
I will focus on interacting physics of the topological Chern insulator and demonstrate numerical evidences
that fractionalized topological phase emerges in flat topological band models with strongly interacting particles,
as the examples of fractional quantum Hall effect without a magnetic field. I will present new results of
obtaining modular matrix using the minimal entangled states, which characterizes the topological order and
quasi-particle statistics of the quantum state.
