BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//RLASKEY//CALENDEROUS//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
DTSTAMP:20181113T175736Z
LAST-MODIFIED:20180731T143822Z
DTSTART:20180806T150000Z
DTEND:20180806T160000Z
UID:event1955@bu.edu
URL:http://physics.bu.edu/events/show/1955
SUMMARY:Boosted one-dimensional superfluids on a lattice
DESCRIPTION:Featuring Sayonee Ray\, University of New Mexico\, CQuIC\nHoste
d by: Christopher Laumann\n\nPart of the Condensed Matter Theory Seminar Se
ries.\n\nWe study the effect of a boost (Fermi sea displaced by a finite mo
mentum) on one dimensional systems of lattice fermions with short-ranged in
teractions. In the absence of a boost such systems with attractive interact
ions possess algebraic superconducting order. Motivated by physics in highe
r dimensions\, one might naively expect a boost to weaken and ultimately de
stroy superconductivity. However\, we show that for one dimensional systems
the effect of the boost can be to strengthen the algebraic superconducting
order by making correlation functions fall off more slowly with distance.
This phenomenon can manifest in interesting ways\, for example\, a boost ca
n produce a Luther-Emery phase in a system with both charge and spin gaps b
y engendering the destruction of the former.\n\nAUTHORS: Sayonee Ray\, Subr
oto Mukerjee and Vijay B. Shenoy
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20181113T175736Z
LAST-MODIFIED:20180904T164820Z
DTSTART:20180907T160000Z
DTEND:20180907T170000Z
UID:event2013@bu.edu
URL:http://physics.bu.edu/events/show/2013
SUMMARY:Universal dynamics in an isolated quantum many body system far from
equilibrium
DESCRIPTION:Featuring Joerg Schmiedmayer\, Vienna Center for Quantum Scienc
e and Technology\, Atominstitut\, TU-Wien\nHosted by: Anatoli Polkovnikov\n
\nPart of the Condensed Matter Theory Seminar Series.\n\nWe provide experim
ental evidence of universal dynamics far from equilibrium during the relaxa
tion of an isolated one-dimensional Bose gas. Following a rapid cooling que
nch\, the system exhibits universal scaling in time and space\, associated
with the approach of a non-thermal fixed point. The time evolution within t
he scaling period is described by a single universal function and scaling e
xponent\, independent of the species of the initial state. Our results prov
ide a quantum simulation in a regime\, where to date no theoretical predict
ions are available. This constitutes a crucial step in the verification of
universality far from equilibrium. If successful\, this may lead to a compr
ehensive classification of systems based on their universal properties far
from equilibrium\, relevant for a large variety of systems at different sca
les.\n\nThis work was supported by the ERC (QuantumRelax) and the DFG/FWF S
FB ISOQUANT.\n\nS. Erne et al. arXiv:1805.12310
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20181113T175736Z
LAST-MODIFIED:20180912T153133Z
DTSTART:20180914T160000Z
DTEND:20180914T170000Z
UID:event2016@bu.edu
URL:http://physics.bu.edu/events/show/2016
SUMMARY:Activating many-body localization in solids by driving with light
DESCRIPTION:Featuring Zala Lenarčič\, University of Cologne\, Institute f
or Theoretical Physics\n\nPart of the Condensed Matter Theory Seminar Serie
s.\n\nCoupling to phonons prevents many body localization (MBL) from occurr
ing in disordered solids even when the disorder is strong. This is because
phonons mediate non-local interaction which weakly breaks local conservatio
n laws characteristic for the MBL phase. Nevertheless\, I will show that de
cay of local conservation laws can be compensated when the system is driven
out of equilibrium. We propose to detect the fingerprints of an underlying
MBL phase by measuring the variation of local temperatures in the resultin
g steady state.\n \nThe concrete example I will consider is a one-dimension
al disordered spin-chain which is weakly coupled to a phonon bath and weakl
y irradiated by white light. The irradiation has weak effects in the ergodi
c phase. However\, if the system is in the MBL phase irradiation induces st
rong temperature variations of order 1. Temperature variations can be used
similar to an order parameter to detect MBL phases\, the phase transition\,
an MBL correlation length and even the critical exponents.\n \nZ. Lenarcic
\, E. Altman\, and A. Rosch\, arXiv:1806.04772 (2018)
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20181113T175736Z
LAST-MODIFIED:20180919T141536Z
DTSTART:20180919T184500Z
DTEND:20180919T194500Z
UID:event2006@bu.edu
URL:http://physics.bu.edu/events/show/2006
SUMMARY:"The Hall number of Strongly Correlated metals"
DESCRIPTION:Featuring Assa Auerbach\, Physics Department\, Technion\nHosted
by: Anatoli Polkovnikov\n\nPart of the Condensed Matter Theory Seminar Ser
ies.\n\nAn exact formula for the temperature dependent Hall number of metal
s is derived. It is valid for non-relativistic fermions or bosons\, with ar
bitrary potential and interaction. This DC transport coefficient is proven
to (remarkably) depend solely on equilibrium susceptibilities\, which are m
ore amenable to numerical algorithms than the conductivity. An application
to strongly correlated phases is demonstrated by calculating the Hall sign
in the vicinity of Mott phases of lattice bosons.\n\nRef: PRL\, in press\,
and arXiv:1802.04810
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20181113T175736Z
LAST-MODIFIED:20180924T142529Z
DTSTART:20180926T190000Z
DTEND:20180926T200000Z
UID:event2019@bu.edu
URL:http://physics.bu.edu/events/show/2019
SUMMARY:Topological magnon bands and effective Hamiltonians for periodicall
y driven systems
DESCRIPTION:Featuring Greg Fiete\, Northeastern University\nHosted by: Anus
hya Chandran\n\nPart of the Condensed Matter Theory Seminar Series.\n\nThe
effect of spin-orbit coupling in condensed matter systems has received inte
nse study over the past decade\, most notably in the context of topological
band insulators where electron-electron interactions are not essential for
the topological properties. In this talk\, I will focus on the opposite l
imit of strong electronic correlations with spin-orbit coupling. I will de
scribe two different (materials motivated) two-dimensional models in which
the spin-orbit coupling leads to topological band structure in the magnetic
excitations. In the second part of the talk\, I will turn to recent work
describing an approach to achieving effective time-independent Hamiltonians
for periodically driven\, interacting many-particle systems. The method a
grees with the Magnus expansion in the high frequency limit\, but appears t
o also work well in the strong-driving\, low-frequency limit.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20181113T175736Z
LAST-MODIFIED:20180926T142054Z
DTSTART:20181010T190000Z
DTEND:20181010T200000Z
UID:event2020@bu.edu
URL:http://physics.bu.edu/events/show/2020
SUMMARY:Vestigial orders in electronic correlated systems: nematicity and b
eyond
DESCRIPTION:Featuring Rafael Fernandes\, University of Minnesota\nHosted by
: Wanzheng Hu\n\nPart of the Condensed Matter Theory Seminar Series.\n\nA h
allmark of the phase diagrams of correlated electronic systems is the exist
ence of multiple electronic ordered states. In many cases\, they cannot be
simply described as independent competing phases\, but instead display a co
mplex intertwinement. A prime example of intertwined states is the case of
primary and vestigial phases. While the former is characterized by a multi-
component order parameter\, the fluctuation-driven vestigial state is chara
cterized by a composite order parameter formed by higher-order\, symmetry-b
reaking combinations of the primary order parameter. This concept has been
widely employed to elucidate nematicity in both iron-based and cuprate supe
rconductors. In this talk\, I will present a group-theoretical framework\,
supplemented by microscopic calculations\, that extends this notion to a va
riety of phases\, providing a general classification of vestigial orders of
unconventional superconductors and density-waves. Electronic states with s
calar and vector chiral order\, spin-nematic order\, Ising-nematic order\,
time-reversal symmetry-breaking order\, and algebraic vestigial order emerg
e from this simple underlying principle. I will present a rich variety of p
ossible phase diagrams involving the primary and vestigial orders\, and dis
cuss possible realizations of these exotic composite orders in different ma
terials.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20181113T175736Z
LAST-MODIFIED:20181010T134629Z
DTSTART:20181017T190000Z
DTEND:20181017T200000Z
UID:event2030@bu.edu
URL:http://physics.bu.edu/events/show/2030
SUMMARY:Hierarchical Majoranas in a Programmable Nanowire Network
DESCRIPTION:Featuring Zhicheng Yang\, Boston University\, Physics Departmen
t\nHosted by: Claudio Chamon\n\nPart of the Condensed Matter Theory Seminar
Series.\n\nWe propose a hierarchical architecture for building "logical" M
ajorana zero modes using "physical" Majorana zero modes at the Y-junctions
of a hexagonal network of semiconductor nanowires. Each Y-junction contains
three "physical" Majoranas\, which hybridize when placed in close proximit
y\, yielding a single effective Majorana mode near zero energy. The hybridi
zation of effective Majorana modes on neighboring Y-junctions is controlled
by applied gate voltages on the links of the honeycomb network. This gives
rise to a tunable tight-binding model of effective Majorana modes. We show
that selecting the gate voltages that generate a Kekule vortex pattern in
the set of hybridization amplitudes yields an emergent "logical" Majorana z
ero mode bound to the vortex core. The position of a logical Majorana can b
e tuned adiabatically\, without moving any of the "physical" Majoranas or c
losing any energy gaps\, by programming the values of the gate voltages to
change as functions of time. A nanowire network supporting multiple such "l
ogical" Majorana zero modes provides a physical platform for performing adi
abatic non-Abelian braiding operations in a fully controllable manner.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20181113T175736Z
LAST-MODIFIED:20181024T143054Z
DTSTART:20181024T190000Z
DTEND:20181024T200000Z
UID:event2024@bu.edu
URL:http://physics.bu.edu/events/show/2024
SUMMARY:Anomalous metals
DESCRIPTION:Featuring Boris Spivak\, University of Washington\nHosted by: C
hristopher Laumann\n\nPart of the Condensed Matter Theory Seminar Series.\n
\nThe observation of metallic ground states in a variety of two-dimensional
electronic\nsystems poses a fundamental challenge for the theory of electr
on fluids. I will analyze\nevidence for the existence of a regime\, which w
e call the "anomalous metal regime\,"\nin diverse 2D superconducting system
s driven through a quantum superconductor to\nmetal transition by tuning ph
ysical parameters such as the magnetic field\,\nthe gate voltage in the cas
e of systems with a MOSFET geometry\, or the degree of\ndisorder. The princ
ipal phenomenological observation is that in the anomalous metal\,\nas a fu
nction of decreasing temperature\, the resistivity first drops as if the sy
stem were\napproaching a superconducting ground state\, but then saturates
at low temperatures to\na value that can be orders of magnitude smaller tha
n the Drude value. The anomalous\nmetal also shows a giant positive magneto
-resistance. Thus\, it behaves as if it were a\nfailed superconductor." Thi
s behavior is observed in a broad range of parameters. I will exhibit\, by
theoretical solution of a model of superconducting grains embedded\nin a me
tallic matrix\, that as a matter of principle such anomalous metallic behav
ior can\noccur in the neighborhood of a quantum superconductor-metal transi
tion. However\, I will also argue that the robustness and ubiquitous nature
of the observed phenomena are difficult to reconcile with any\nexisting th
eoretical treatment\, and speculate about the character of a more fundament
al\ntheoretical framework.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
BEGIN:VEVENT
DTSTAMP:20181113T175736Z
LAST-MODIFIED:20181015T202142Z
DTSTART:20181212T200000Z
DTEND:20181212T210000Z
UID:event2022@bu.edu
URL:http://physics.bu.edu/events/show/2022
SUMMARY:Tunneling-induced restoration of classical degeneracy in quantum ka
gome ice
DESCRIPTION:Featuring Ying-Jer Kao\, National Taiwan University and BU\nHos
ted by: Anders Sandvik\n\nPart of the Condensed Matter Theory Seminar Serie
s.\n\nQuantum effect is expected to dictate the behavior of physical system
s at \nlow temperature. For quantum magnets with\ngeometrical frustration\,
quantum fluctuation lifts the macroscopic \nclassical degeneracy\, and exo
tic quantum states\nemerge. However\, how different types of quantum proces
ses entangle wave \nfunctions in a constrained Hilbert space is not\nwell u
nderstood. Here\, we study the topological entanglement entropy and \nthe t
hermal entropy of a quantum ice model on a\ngeometrically frustrated kagome
lattice. We find that the system does not \nshow a Z_2 topological order d
own to extremely\nlow temperatures\, yet continues to behave like a classic
al kagome ice with \nfinite residual entropy. Our theoretical\nanalysis ind
icates that an intricate competition of off-diagonal and \ndiagonal quantum
tunneling processes leading to a\nsuppression of the quantum energy scale.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
END:VCALENDAR