We observed and controlled the Brownian motion of solitons. We launched solitonic excitations in highly elongated Rb-87 Bose-Einstein condensates (BECs) and showed that a dilute background of impurity atoms in a different internal state dramatically affects the soliton. With no impurities and in one dimension (1D), these solitons would have an infinite lifetime, a consequence of integrability. In our experiment, the added impurities scatter off the much larger soliton, contributing to its Brownian motion and decreasing its lifetime. We describe the soliton{\textquoteright}s diffusive behavior using a quasi-1D scattering theory of impurity atoms interacting with a soliton, giving diffusion coefficients consistent with experiment.

}, issn = {0027-8424}, doi = {10.1073/pnas.1615004114}, author = {Aycock, Lauren M. and Hurst, Hilary M. and Efimkin, Dmitry K. and Genkina, Dina and Lu, Hsin-I and Galitski, Victor M. and Ian B Spielman} } @article { ISI:000413897900001, title = {Enriched axial anomaly in Weyl materials}, journal = {PHYSICAL REVIEW B}, volume = {96}, number = {16}, year = {2017}, month = {OCT 30}, issn = {2469-9950}, doi = {10.1103/PhysRevB.96.161115}, author = {Raines, Zachary M. and Galitski, Victor M.} } @article {ISI:000400772100005, title = {Exactly soluble model of boundary degeneracy}, journal = {PHYSICAL REVIEW B}, volume = {95}, number = {4}, year = {2017}, month = {JAN 25}, abstract = {We investigate the topological degeneracy that can be realized in Abelian fractional quantum spin Hall states with multiply connected gapped boundaries. Such a topological degeneracy (also dubbed as {\textquoteleft}{\textquoteleft}boundary degeneracy{{\textquoteright}{\textquoteright}}) does not require superconducting proximity effect and can be created by simply applying a depletion gate to the quantum spin Hall material and using a generic spin-mixing term (e.g., due to backscattering) to gap out the edge modes. We construct an exactly soluble microscopic model manifesting this topological degeneracy and solve it using the recently developed technique {[}S. Ganeshan and M. Levin, Phys. Rev. B 93, 075118 (2016)]. The corresponding string operators spanning this degeneracy are explicitly calculated. It is argued that the proposed scheme is experimentally reasonable.}, issn = {2469-9950}, doi = {10.1103/PhysRevB.95.045309}, author = {Ganeshan, Sriram and Gorshkov, Alexey V. and Gurarie, Victor and Galitski, Victor M.} } @article {7261, title = {Time-reversal symmetry-breaking superconductivity in epitaxial bismuth/nickel bilayers}, journal = {Science Advances}, volume = {3}, year = {2017}, abstract = {Superconductivity that spontaneously breaks time-reversal symmetry (TRS) has been found, so far, only in a handful of three-dimensional (3D) crystals with bulk inversion symmetry. We report an observation of spontaneous TRS breaking in a 2D superconducting system without inversion symmetry: the epitaxial bilayer films of bismuth and nickel. The evidence comes from the onset of the polar Kerr effect at the superconducting transition in the absence of an external magnetic field, detected by the ultrasensitive loop-less fiber-optic Sagnac interferometer. Because of strong spin-orbit interaction and lack of inversion symmetry in a Bi/Ni bilayer, superconducting pairing cannot be classified as singlet or triplet. We propose a theoretical model where magnetic fluctuations in Ni induce the superconducting pairing of the orbital symmetry between the electrons in Bi. In this model, the order parameter spontaneously breaks the TRS and has a nonzero phase winding number around the Fermi surface, thus making it a rare example of a 2D topological superconductor.

}, doi = {10.1126/sciadv.1602579}, url = {http://advances.sciencemag.org/content/3/3/e1602579}, author = {Gong, Xinxin and Kargarian, Mehdi and Stern, Alex and Yue, Di and Zhou, Hexin and Jin, Xiaofeng and Galitski, Victor M. and Yakovenko, Victor M. and Xia, Jing} } @article {ISI:000396271900006, title = {Topological spin ordering via Chern-Simons superconductivity}, journal = {PHYSICAL REVIEW B}, volume = {95}, number = {9}, year = {2017}, month = {MAR 15}, pages = {094511}, abstract = {We use the Chern-Simons (CS) fermion representation of s = 1/2 spin operators to construct topological, long-range magnetically ordered states of interacting two-dimensional (2D) quantum spin models. We show that the fermion-fermion interactions mediated by the dynamic CS flux attachment may give rise to Cooper pairing of the fermions. Specifically, in an XY model on the honeycomb lattice, this construction leads to a {\textquoteleft}{\textquoteleft}CS superconductor{{\textquoteright}{\textquoteright}}, which belongs to a topologically nontrivial in 2D symmetry class DIII, with particle-hole and time-reversal symmetries. It is shown that in the original spin language, this state corresponds to a symmetry protected topological state, which coexists with a magnetic long-range order. We discuss physical manifestations of the topological character of the corresponding state.}, issn = {2469-9950}, doi = {10.1103/PhysRevB.95.094511}, author = {Sedrakyan, Tigran A. and Galitski, Victor M. and Kamenev, Alex} } @article { ISI:000365507200003, title = {Hybridization of Higgs modes in a bond-density-wave state in cuprates}, journal = {PHYSICAL REVIEW B}, volume = {92}, number = {18}, year = {2015}, month = {NOV 24}, issn = {1098-0121}, doi = {10.1103/PhysRevB.92.184511}, author = {Raines, Zachary M. and Stanev, Valentin G. and Galitski, Victor M.} } @article {4090, title = {Statistical Transmutation in Floquet Driven Optical Lattices}, journal = {Phys. Rev. Lett.}, volume = {115}, year = {2015}, month = {Nov}, pages = {195301}, doi = {10.1103/PhysRevLett.115.195301}, url = {http://link.aps.org/doi/10.1103/PhysRevLett.115.195301}, author = {Sedrakyan, Tigran A. and Galitski, Victor M. and Kamenev, Alex} }