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Agenda
Wolfgang Ketterle (MIT) Introduction, overview 15Markus Greiner (Harvard) Quantum gas microscopy 25Eugene Demler (Harvard) Exploring exotic states of matter
with interference 20
Quantum dynamics far away from equilibriumUlrich Schneider (Munich) Emergence of coherence at
a quantum phase transition 20Coffee breakJoseph Thywissen (Toronto) Spin dynamics of fermions 10Tarik Yefsah (MIT) Solitary waves in fermionic superfluids 10
Nikolai Prokof'ev (Amherst) New theoretical methods 15Wolfgang Ketterle (MIT) Synthetic magnetic fields in
optical lattices 20
Exploring exotic states of matter with interference
Eugene Demler (Harvard)
Collaborators:S. Gopalakrishnan, M. Knap, M. Lukin, T. Kitagawa (Harvard) D. Abanin (Harvard/Perimeter Inst.), M. Serbyn (MIT),M. Atala, M. Aidelsburger, J. Barreiro, I. Bloch (MPQ/LMU)A. Kantian, T. Giamarchi (Univ. Geneva)
Antiferromagnetic and superconducting Tc of the order of 100 K
Atoms in optical lattice
Antiferromagnetism and pairing at sub-micro Kelvin temperatures
Same microscopic model
Quantum simulations with ultracold atoms
How to detect many-body phases with ultracold atoms
/2 pulse
Evolution
Ramsey interference
Used for atomic clocks, gravitometers, accelerometers, magnetic field measurements
pulse + measurement of Sz gives relative phase accumulated by the two spin components
EvolutionEvolution
Outline
Exploring exotic states of matter with interference
Measuring Berry/Zak phase in optical latticesM. Atala et al., Nature Physics (2013), T. Kitagawa et al., PRL (2013)
Measuring dynamical spin correlation functionsM. Knap, et al., Phys. Rev. Lett. (2013)
Probing many-body localizationM. Serbyn, M. Knap, S. Gopalakrishnan, et al.
Probing band topology with Ramsey/Bloch interference
Theory: D. Abanin, T. Kitagawa, E. Demler
Experiments: M. Atala, M. Aidelsburger, J. Barreiro, I. Bloch (MPQ/LMU)
M. Atala et al., Nature Physics (2013), T. Kitagawa et al., PRL (2013)
Broken symmetries vs topological order
Order parameters
Berry/Zak phase in 1d
How to measure topological order parameter?
accuracy 10-9
SSH Model with bichromatic lattice
B A B BA
When dz(k)=0, states with t>0 and t<0 are topologically distinct.We can not deform two paths into each other without closing the gap.
Characterizing SSH model using Zak phase Two hyperfine spin states experience the same optical potential
/2a/2a
a
Zak phase is equal to 0
Zak/Berry phase measurements
Exploring dynamical response functions in spin modelsusing many-body Ramsey interference
M. Knap, A. Kantian, T. Giamarchi, I. Bloch, M. Lukin, E. DemlerPhys. Rev. Lett. (2013)
Cold atoms Trapped ions Dipolar interactions
Heisenberg model of XXZ type
super-exchange
e.g. 87Rb mixtures ofand
LR transverse field Ising model
interactions mediated by phonons
e.g. 171Yb
LR XX model
Molecules, e.g. KRb
Atoms w/ large magnetic moments, e.g. Cr
MPQ group JQI group JILA group
Probing spin dynamics in synthetic matter
Many‐body spin Ramsey protocol
Measures the retarded spin correlation function
Systems with interactions and disorder Granular superconductors and Josephson junction networks
– Crane et al. (2007): AC response– Bouadim et al. (2011): numerics– Baturina, Sacepe et. al. (2008): STM– Trivedi et. al. (2012 review)
Central spin problem in q-dotsNV centers in diamond
- Marcus et al. (2004) - Lukin et al. (2006)- Jelezko et a. (2007)- Awschalom et al. (2007)
Polar molecules in optical lattices– Ye et al. (2013)
Rydberg atoms– Ryabtsev et al. (2010)– Bloch et al. (2012)
Gap map in TiN film
Nuclear spin interactions mediated by electron spin
Angular momentum as spin degree of freedom
Strong interactions due to large electric dipole moment
Many-body localization (MBL)
localization in the presence of interactions
system does not act as its own bath (discrete local spectrum)
MBL states vs. Anderson localized states→ interactions create non-local correlations (growth of entanglement)
Bardarson et al., PRL (2012)Vosk, Altman, PRL (2013)Serbyn, et al. PRL (2013)
Temperature
Cond
uctiv
ity
Not activatedconductivity
– Anderson– Basko, Aleiner, Altshuler– Huse, Oganesyan, Pal– Aleiner, Altshuler, Shlyapnikov– …
Spin correlation function as quantum quench
In a localized phase, local quench affectsonly a few excitations. For each eigenstateexpect non‐decaying oscillations
In a delocalized phase (diffusive regime), local quench affects all excitations. Expect decayakin orthogonality catastrophe
After averaging over thermal ensemble(and/or disorder realizization) find decay
Spin correlation function as quantum quench
Ramsey + spin echoM. Knap, S. Gopalakrishnan, M. Serbyn, et al.
“Cartoon” model of the localized phase
Spin echo
M. Knap, S. Gopalakrishnan, M. Serbyn, et al.
Double Electron‐Electron Resonance Ramsey sequence
Double Electron‐Electron Resonance Ramsey sequence
single realizationthermal averaging over 50 eigenstates
For a given time t we can separate fast modesand slow modes
Interaction strength decays as
“Cartoon” model of MBL phase
MBL as integrable model
Double Electron‐Electron Resonance Ramsey sequence
Summary
Exploring exotic states of matter with interference
Measuring Berry/Zak phase in optical latticesM. Atala et al., Nature Physics (2013), T. Kitagawa et al., PRL (2013)
Measuring dynamical spin correlation functionsM. Knap, et al., Phys. Rev. Lett. (2013)
Probing many-body localizationM. Serbyn, M. Knap, S. Gopalakrishnan, et al.