Bulletin of the American Physical Society
53rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 67, Number 7
Monday–Friday, May 30–June 3 2022; Orlando, Florida
Session E08: Quantum Gases in Low Dimensions IRecordings Available

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Chair: Colin Parker, Georgia Tech Room: Salon 7/8 
Tuesday, May 31, 2022 2:30PM  2:42PM 
E08.00001: Spincharge separation in a 1D Fermi gas with tunable interactions Ruwan Senaratne, Danyel CavazosCavazos, Sheng Wang, Feng He, Aashish Kafle, YaTing Chang, Han Pu, Xiwen Guan, Randall G Hulet Ultracold atoms confined in optical lattices are a powerful tool for quantum simulation of complex manybody systems. We confine spin1/2 atomic fermions (^{6}Li) to one dimension and realize the YangGaudin model, the lowenergy behavior of which is expected to be that of a TomonagaLuttinger liquid [1]. Such liquids exhibit bosonic collective lowenergy excitations and spincharge separation. Using Bragg spectroscopy and a Feshbach resonance, we directly excite either the spin or charge wave with a tunable repulsive interaction strength. We observe the onset of spincharge separation as interactions are increased from zero. The spin and charge excitation velocities are equal for the noninteracting case, while the chargemode velocity increases and the spinmode velocity decreases with increasing interaction, a hallmark of spincharge separation. The excitation spectra provide access to the dynamic structure factors of each mode, which are in quantitative agreement with the TomonagaLuttinger liquid theory, including nonlinear corrections due to bandcurvature and backscattering. 
Tuesday, May 31, 2022 2:42PM  2:54PM 
E08.00002: Observation of confinementinduced background dimers in a 1D Fermi Gas Danyel CavazosCavazos, Ruwan Senaratne, Aashish Kafle, Randall G Hulet Ultracold atoms confined to optical lattices enable systematic studies of quantum systems in reduced dimensions. Dimensionality effects are particularly prominent in their ability to modify the twobody bound and scattering states. In free space, for example, Feshbach dimers exist only on the positive scattering length side of the Feshbach resonance, while in harmonicallyconfined, onedimensional (1D) systems weakly bound molecular states have been observed on both sides of the corresponding confinementinduced resonance. Moreover, a combination of quasi1D confinement and a negative, swave background scattering length is predicted to give rise to a weaklybound molecular state with a wavefunction that extends well beyond the interparticle spacing, known as a confinementinduced background (CIB) dimer [1]. Contrary to the formation of weaklybound Feshbach dimers, the threshold for CIB dimer formation occurs far from the Feshbach resonance. Rather, it takes place at the zerocrossing of the scattering length, where the effective 1D scattering length has a pole. Here, we report the first observation of CIB dimers in a 1D Fermi gas. We realize a pseudospin1/2 system with the lowest and thirdtolowest, 1〉3〉, hyperfine sublevels of ^{6}Li. The atoms are loaded into a 2D optical lattice, thus creating an array of quasi1D atomic waveguides. We characterize the binding energies and the population ratio between dimers and unpaired atoms in the gas using radiofrequency spectroscopy for different confinement strengths. Although the binding energy of the CIB shallow bound state is comparable to the Fermi energy, we observe them to exhibit long (> 1s) lifetimes, perhaps because of their highlyextended anisotropic wavefunction. We will also discuss their manybody properties in 1D. 
Tuesday, May 31, 2022 2:54PM  3:06PM 
E08.00003: Fractional excitations and spinincoherent liquids in 1D Hubbard model Xiwen Guan, Han Pu, JiaJia Luo The Hubbard model has become increasingly important in condensed matter physics, quantum metrology and quantum information. In this talk, we will discuss fractional excitations and spinincoherent liquids in the 1D repulsive FermiHubbard model with di erent magnetic elds and llings. Using Bethe ansatz solution, we rigorously show that the fractional spin and charge excitations display di erent features of spincharge separation in various lling limits. For a dilute lled lattice, the interplay between the charge and the spin degrees of freedom can disrupt the coherent Luttinger liquids of spin and charge, giving rise to the socalled spinincoherent liquid. Whereas near the halflling limit, the charge velocity is exponentially suppressed, which means that the system enters the quantum critical regime, thus there exists neither spin nor chargeincoherent liquids. Furthermore, we determine universal behaviour of such spincoherent and incoherent liquids in the vicinities of different phase transitions. 
Tuesday, May 31, 2022 3:06PM  3:18PM 
E08.00004: Topological Exchange Statistics in One Dimension Nathan L Harshman, Adam C Knapp The standard topological approach to indistinguishable particles formulates exchange statistics by using the fundamental group to analyze the connectedness of the configuration space. Although successful in two and more dimensions, this approach gives only trivial or near trivial exchange statistics in one dimension because twobody coincidences are excluded from configuration space. Instead, we include these pathambiguous singular points and consider configuration space as an orbifold. This orbifold topological approach allows unified analysis of exchange statistics in any dimension and predicts novel possibilities for anyons in onedimensional systems, including nonabelian anyons obeying alternate strand groups. It also clarifies the nontopological origin of fractional statistics in onedimensional anyon models. 
Tuesday, May 31, 2022 3:18PM  3:30PM 
E08.00005: Radiofrequency spectroscopy near a pwave Feshbach resonance in one dimension Kenneth G Jackson, Colin J Dale, Kevin G. S. Xie, Ben A Olsen, Jeff A Maki, Shizhong Zhang, Joseph H Thywissen We study scattering of identical fermions confined in two orthogonal standing waves near a pwave Feshbach resonance. By varying the lattice depth and magnetic field, we observe the confinement induced resonance shift and compare to recent parameterizations of this resonance. By performing fast radiofrequency (rf) spectroscopy, we measure the dependence of the rf spectrum on onedimensional (1D) interaction strength. We relate the rf transfer rate through universal relations to the 1D pwave contact, which is a measure of correlation strength in the gas. By amplitude modulating and frequency modulating the optical lattice, we test the influence of band population on the observed rf spectra. 
Tuesday, May 31, 2022 3:30PM  3:42PM 
E08.00006: Thermodynamic contacts and breathing mode physics of 1D oddwave Fermi gases in the high temperature limit Jeff A Maki An important tool for understanding the effects of interactions in harmonically trapped atomic gases is the examination of their collective modes. One such mode is the breathing or monopole mode, which is special as it is constrained to occur at twice the harmonic trapping frequency when the interactions are scale invariant. When the interactions are not scale invariant, the frequency of the breathing mode will deviate from twice the trap frequency. The deviation itself depends on the thermodynamic contacts, which describe how the energy changes with the interactions. In this talk I study the thermodynamic contacts and the breathing mode of a spinolarized onedimensional Fermi gas with odd wave interactions in the hightemperature limit. In this case, the energy dependence of the interactions, characterized by the effective range, can not be neglected. I explicitly show how the breathing mode changes with interaction strength from weak to strong interactions for a finite effective range. Such dynamics can be studied in experiments and provide a tool for understanding how the dynamics depend on interactions with a finite effective range. 
Tuesday, May 31, 2022 3:42PM  3:54PM 
E08.00007: An algebraic geometric classification of the solutions of the 1D GrossPitaevskii equation David Reinhardt, Matthias Meister, Dean J Lee, Wolfgang P Schleich The stationary solutions of the Schrödinger equation with box or periodic boundaries show a clear correspondence to solutions found for the nonlinear GrossPitaevskii equation commonly used to model BoseEinstein condensates. However, in the nonlinear case there exists an additional class of solutions for periodic boundaries first identified by L.D. Carr et al. [1]. These nodeless solutions have no corresponding counterpart in the linear case. To fully classify these solutions and to understand their origin, we study the underlying algebraic geometry. Therefore, we treat both equations in the hydrodynamic framework, resulting in a firstorder differential equation for the density determined by a quadratic polynomial in the linear case and by a cubic polynomial in the nonlinear case, respectively. Our approach allows for a clear geometric interpretation and complete classification of the solution space in terms of the nature and location of the roots of these polynomials. Furthermore, we consider possible generalizations of our method towards higher dimensional systems and beyondmeanfield corrections. 
Tuesday, May 31, 2022 3:54PM  4:06PM 
E08.00008: Mobile dissipative impurities in onedimensional Bose gases Martin Will, Jamir Marino, Michael Fleischhauer We study an impurity immersed into a onedimensional Bose gas with a fluctuating impurityBose interaction (i.e. a dissipative „polaron“). We use a meanfield description which takes the deformation of the quasi condensate into account such that quantum fluctuations are small. The stochastic coupling creates a coherent flow of particles towards the impurity, similar to the effect of a local loss. In addition there is an outward flowing incoherent current of particles. Depending on the amplitude of the noise and the velocity of the impurity a normal or Zenolike quasi stationary state emerges. Above a critical value of the velocity there is a continuous emission of solitons such that no stationary state forms even for a subsonic impurity. In the case of two impurities, we find evidence for a dissipationmediated longrange interaction between the impurities for weak noise, while strong noise results, similar as a moving impurity, in a constant creation of solitons. 
Tuesday, May 31, 2022 4:06PM  4:18PM 
E08.00009: Measuring Rapidities of a Bosonic Dipolar 1D Quantum Gas in Tonks and SuperTonks Regimes Kangning Yang, KuanYu Li, KuanYu Lin, Sarang Gopalakrishnan, Benjamin L Lev, Yicheng Zhang, Marcos Rigol The distribution of rapidities—quasimomenta of a onedimensional (1D) manybody system that depends on the interactions within particles—are of great interest in characterizing manybody states. The bosonic 1D dipolar gas, with its integrabilitybreaking longrange interactions, is a perfect platform to explore rapidity distributions in a nearly integrable system. We report the measurement of rapidity distributions in a 1D dipolar quantum gas of dysprosium, where we use a Feshbach resonance to tune the shortrange interaction strength and a magnetic field angle to tune the longrange dipoledipole interaction sign and strength. In addition to ground state measurements, we also topologically pump the gas into superTonks regime to measure the rapidities of prethermal longlived excited states (akin to manybody scar states). 
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