Scale invariance emerges and plays an important role in strongly correlated many-body systems such as critical regimes nearby phase transitions and the unitary Fermi gases. Discrete scaling symmetry also manifests itself in quantum few-body systems such as the Efimov effect. Here we report both theoretical predication and experimental observation of a novel type expansion dynamics for scale invariant quantum gases. When the frequency of the harmonic trap holding the gas decreases continuously as the inverse of time t, surprisingly, the expansion of cloud size exhibits a sequence of plateaus. Remarkably, the locations of these plateaus obey a discrete geometric scaling law with a controllable scale factor and the entire expansion dynamics is governed by a log-periodic function. This striking expansion of quantum Fermi gases shares similar scaling laws and same mathematical description as the Efimov effect. Our work demonstrates the first expansion dynamics of a quantum many-body system with the temporal discrete scaling symmetry, which reveals the underlying spatial continuous scaling symmetry of the many-body system.Interaction between dilute ultracold atoms is described by the s-wave scattering length. For a spin-1/2 Fermi gas, when the scattering length diverges at a Feshbach resonance, there is no length scale other than the interparticle spacing in this many-body system, and therefore the system, known as the unitary Fermi gas, becomes scale invariant. The spatial scale invariance leads to universal thermodynamics and transport properties as revealed by many experiments [1][2][3][4][5][6][7][8][9][10][11][12][13]. On the other hand, in a boson system with an infinite scattering length, threebody bound state can form, where an extra length scale of the three-body parameter sets a short-range boundary condition for all three bosons being very close. It turns the continuous scaling symmetry into a discrete scaling symmetry, and gives rise to infinite number of three-body bound states whose energies obey a geometric scaling symmetry. This is well known as the Efimov effect [14,15], which has been observed in quite a few cold atom experiments [16][17][18][19][20][21][22][23][24], and recent experiments have also confirmed the geometric scaling of the energy spectrum [25][26][27][28]. Both the continuous and the discrete scaling symmetry are interesting emergent phenomena in a strongly interacting system. For a harmonic trapped gas, the expansion dynamics offers great insight to the property of the gas. Well known example is the anisotropic expansion that proves hydrodynamics behavior due to the Bose condensation [29,30] or strong interactions of Fermi gas [31]. Other examples are, for instance, slowing down of expansion in a disorder potential provides evidence for localization behaviors [32,33] and expansion in the presence of optical lattice reveals correlation effects [34]. In this work, we ask a question that, considering a scale invariant quantum gas hold by a harmonic trap, when the trap is gradually opened...

In this letter we show that the recently theoretically predicted and experimentally observed "orbital Feshbach resonance" in alkali-earth-like 173 Yb atom is a narrow resonance in energy, while it is hundreds Gauss wide in term of magnetic field strength, taking the advantage that the magnetic moment difference between the open and closed channels is quite small. Therefore this is an ideal platform for the experimental realization of a strongly interacting Fermi superfluid with narrow resonance. We show that the transition temperature for the Fermi superfluid in this system, especially at the BCS side of the resonance, is even higher than that in a wide resonance, which is also due to the narrow character of this resonance. Our results will encourage experimental efforts to realize Fermi superfluid in the alkali-earth-like 173 Yb system, the properties of which will be complementary to extensively studied Fermi superfluids nearby a wide resonance in alkali 40 K and 6 Li systems.Pairing of fermions is a universal mechanism for both superconductivity in materials and Fermi superfluid in neutral atoms. In the weakly attractive BCS regime, the transition temperature T c is much smaller than the Fermi temperature T F [1]. In cold atom systems, the Feshbach resonance (FR) provides a tool to significantly enhance the attraction between atoms [2, 3], with which the T c can be increased to the order of 0.1T F [4, 5]. So far, in term of T c /T F , this is the highest transition temperature ever achieved and in the past decade or so it has been realized and extensively studied by many laboratories with 40 K and 6 Li atoms [4, 5].Interactions between ultracold atomic gases are usually dominated by s-wave scattering and can be well described by the s-wave phase shift θ k , which can be expanded as [2][3][4] where k is the relative momentum between two atoms. The leading order term gives the scattering length a s which diverges at a resonance. The next order term is characterized by an effective range r 0 , which describes how fast the scattering phase shift changes in energy. Effective range also controls how sensitive the a s depends on the magnetic field strength. Normally around a FR the magnetic field dependence of a s can be casted intowhere B res is the field location of a FR, a bg is so-called the background scattering length, ∆ B is the resonance width. Neglecting the short range van de Waals physics, ∆ B is related to r 0 via [6,7] where m is the single-atom mass and δµ is the magnetic moment difference between the open and closed channels. A resonance can be classified as a wide or narrow resonance, depending on how r 0 compares with the characteristic length scales of the system. This length scale could be either van der Waals length r vdW or the inverse of the Fermi momentum 1/k F . One can introduce a parameter called s res = 8πr vdW /(Γ(1/4) 2 |r 0 |), and resonances with s res 1 are called narrow resonances [3]. So far all experiments on fermion superfluid nearby a FR are performed with a wide resonance, such ...

Delivery of high capacity with high thermal and air stability is a great challenge in the development of Ni-rich layered cathodes for commercialized Li-ion batteries (LIBs). Herein we present a surface concentration-gradient spherical particle with varying elemental composition from the outer end LiNiCoMnO (NCM) to the inner end LiNiCoAlO (NCA). This cathode material with the merit of NCM concentration-gradient protective buffer and the inner NCA core shows high capacity retention of 99.8% after 200 cycles at 0.5 C. Furthermore, this cathode material exhibits much improved thermal and air stability compared with bare NCA. These results provide new insights into the structural design of high-performance cathodes with high energy density, long life span, and storage stability materials for LIBs in the future.

We investigate the non-Abelian Josephson effect in F=2 spinor Bose-Einstein condensates with double optical traps. We propose a real physical system which contains non-Abelian Josephson effect and has very different density and spin tunneling characters compared with the Abelian case. We calculate the frequencies of the pseudo Goldstone modes in different phases between two traps, respectively, which are the crucial feature of the non-Abelian Josephson effect. We also give an experimental protocol to observe this novel effect in future experiments.

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Some nuclear proteins that are crucial in interphase relocate during the G2/M-phase transition in order to perform their mitotic functions. However, how they perform these functions and the underlying mechanisms remain largely unknown. Here, we report that a fraction of the nuclear periphery proteins lamin-A/C, LAP2α and BAF1 (also known as BANF1) relocate to the spindle and the cell cortex in mitosis. Knockdown of these proteins by using RNA interference (RNAi) induces short and fluffy spindle formation, and disconnection of the spindle from the cell cortex. Disrupting the microtubule assembly leads to accumulation of these proteins in the cell cortex, whereas depolymerizing the actin microfilaments results in the formation of short spindles. We further demonstrate that these proteins are part of a stable complex that links the mitotic spindle to the cell cortex and the spindle matrix by binding to spindle-associated dynein, the actin filaments in the cell cortex and the spindle matrix. Taken together, our findings unveil a unique mechanism where the nuclear periphery proteins lamin-A/C, LAP2α and BAF1 are assembled into a protein complex during mitosis in order to regulate assembly and positioning of the mitotic spindle.

Many unconventional quantum matters, such as fractional quantum Hall effect and d-wave high-Tc superconductor, are discovered in strongly interacting systems. Understanding quantum many-body systems with strong interaction and the unconventional phases therein is one of the most challenging problems in physics nowadays. Cold atom systems possess a natural way to create strong interaction by bringing the system to the vicinity of a scattering resonance. Although this has been a focused topic in cold atom physics for more than a decade, these studies have so far mostly been limited for s-wave resonance. Here we report the experimental observation of a broad d-wave shape resonance in degenerate 41 K gas. We further measure the molecular binding energy that splits into three branches as a hallmark of d-wave molecules, and find that the lifetime of this many-body system is reasonably long at strongly interacting regime. From analyzing the breathing mode excited by ramping through this resonance, it suggests that a quite stable low-temperature atom and molecule mixture is produced. Putting all the evidence together, our system offers great promise to reach a d-wave molecular superfluid.

It is known from the solution of the two-body problem that an anisotropic dipolar interaction can give rise to s-wave scattering resonances, which are named dipolar interaction induced resonances (DIIR). In this Letter, we study the zero-temperature many-body physics of a two-component Fermi gas across a DIIR. In the low-density regime, it is very striking that the resulting pairing order parameter is a nearly isotropic singlet pairing and the physics can be well described by an s-wave resonant interaction potential with finite range conditions, despite the anisotropic nature of the dipolar interaction. The pairing energy is as strong as a unitary Fermi gas near a magnetic Feshbach resonance. In the high-density regime, the anisotropic effect plays an important role. We find phase transitions from singlet pairing to a state with mixed singlet and triplet pairing and then from mixed pairing to pure triplet pairing. The state with mixed pairing spontaneously breaks the time-reversal symmetry.