Academics

Upcoming Seminars

UMass Boston Physics Colloquia

 

Talks are on Thursdays, 1:00 pm, at S(cience)-3-126, unless stated otherwise

 

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Thursday, January 26, 1:00pm

 

Efi Shahmoon
Harvard U

 

Cooperative resonances in light scattering from atomic metasurfaces

 

We consider light scattering off a two-dimensional (2D) dipolar array and show how it can be tailored by properly choosing the lattice constant of the order of the incident wavelength. In particular, we demonstrate that such arrays can operate as a nearly perfect mirror for a wide range of incident angles and frequencies, and shape the emission pattern from an emitter into a well-defined, collimated beam. These results can be understood in terms of the cooperative resonances of the surface modes supported by the 2D array. Experimental realizations are discussed, using ultracold arrays of trapped atoms and excitons in 2D semiconductor materials, as well as potential applications ranging from atomically thin metasurfaces to single photon nonlinear optics and nanomechanics.

 

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Thursday, Feb 2, 1:00pm

 

NO SEMINAR
 

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Thursday, Feb 9, 1:00pm

 

NO SEMINAR
 

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Thursday, February 16, 1:00pm

 

Tigran Sedrakyan
UMass Amherst

 

Quantum spin-liquid with ulrtacold bosons: the smoking gun of statistical transmutation

 

Optical lattices are remarkable for their capacity to host rich physics. Examples include lattices having moat-like band structures, i.e., a band with infinitely degenerate energy minima attained along a closed line in the Brillouin zone. It is entirely the effect of competing correlations which lifts this degeneracy and leads to an amazing variety of completely new quantum many-body states. If such a lattice is populated with bosons, the degeneracy prevents their condensation. Such degeneracy of the kinetic energy favors fermionic quasiparticles, leading to statistical transmutation. At hard-core repulsion, the system is equivalent to the spin-1/2 XY model, while the absence of condensation translates into the absence of magnetic order in the XY plane. In this talk I will show that the frustration in such lattices stabilizes a variety of novel quantum spin liquid phases including a composite fermion state and a chiral spin liquid. These are topologically ordered states, which may be viewed as states of fermions subject to Chern-Simons gauge fields. They have a bulk gap and chiral gapless edge excitations. The talk includes a suggestion for the chiral spin liquid realizations in experiments with cold atoms. The velocity distribution of the released bosons is a sensitive probe of the statistical transmutation and a chiral spin-liquid state.

 

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Thursday, February 23, 1:00pm

 

TBA
TBA

 

TBA

 

TBA

 

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Thursday, March 2, 1:00pm

 

TBA
TBA

 

TBA

 

TBA

 

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Thursday, March 9, 1:00pm

 

TBA
TBA

 

TBA

 

TBA

 

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Thursday, March 16, 1:00pm

 

NO SEMINAR, SPRING BREAK
 

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Thursday, March 23, 1:00pm

 

TBA
TBA

 

TBA

 

TBA

 

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Thursday, March 30, 1:00pm

 

TBA
TBA

 

TBA

 

TBA

 

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Thursday, April 6, 1:00pm

 

NO SEMINAR
 

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Thursday, April 13, 1:00pm

 

TBA
TBA

 

TBA

 

TBA

 

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Thursday, April 20, 1:00pm

 

TBA
TBA

 

TBA

 

TBA

 

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Thursday, April 27, 1:00pm

 

TBA
TBA

 

TBA

 

TBA

 

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Thursday, May 4, 1:00pm

 

TBA
TBA

 

TBA

 

TBA

 

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