Fate of the Amplitude Mode in a Trapped Dipolar Supersolid

Abstract

We theoretically investigate the spectrum of elementary excitations of a trapped dipolar quantum gas across the BEC-supersolid phase transition. Our calculations reveal the existence of distinct Higgs and Nambu-Goldstone modes that emerge from the softening roton modes of the dipolar BEC at the phase transition point. On the supersolid side of the transition, the energy of the Higgs mode increases rapidly, leading to a strong coupling to higher-lying modes. Our study highlights how the symmetry-breaking nature of the supersolid state translates to finite-size systems.arXiv:1907.09315v1 [cond-mat.quant-gas]

Pattern Formation in Quantum Ferrofluids: from Supersolids to Superglasses

“…When another density minimum is present in the center of the trap, multiple rings with connecting density bridges and honeycomb patterns with six, seven or more density minima form. These structures feature strong density connections, facilitating superfluid flow along the honeycomb pattern [12,74,79,92,127]. In combination with the crystalline structure that develops, these states form a supersolid phase [29,100].…”

“…Understanding that these morphologies are stabilized by repulsive quantum fluctuations [57,59,[70][71][72] was crucial for the experimental discovery of elongated dipolar supersolids in cigar-shaped traps [73][74][75][76][77]. Despite rapid developments in this field, the dipolar supersolids have been experimentally limited to the droplet morphology and mostly one-dimensional (1D) crystal structures [13,68,[73][74][75][76][77][78][79][80][81][82][83][84][85][86], although first steps toward two-dimensional (2D) supersolid droplets have recently been made [87][88][89][90][91]. In an infinite system, the ground-state phase diagram of 2D arrangements of dipolar supersolids showed honeycomb supersolid structures [92].…”

New opportunites for interactions and control with ultracold lanthanides

“…In this context, studies have focused on various excitation modes of the supersolid states, which feature both superfluid and crystaline character. In particular, the emergence of two excitation branches, each related to a spontaneous symmetry breaking, have been experimentally observed via probing symmetric axial compression modes with crystaline, superfluid, and hybrid character [126][127][128], as well as a low-energy Goldstone-mode [129]. Rotational properties have been studied through measurements of angular oscillations [130], and studies of the evaporative formation and phase-locking dynamics of supersolids have explored the process by which phase coherence is established across a supersolid [131].…”

Self-bound dipolar droplets and supersolids in molecular Bose-Einstein condensates

“…Details of our numerical procedure to solve Eq. 1 have been discussed in detail in previous works [16,19,73].…”

“…This counterintuitive behavior leads to a rich phase diagram that contains, for example, self-bound quantum droplets [5,6] and supersolid states [7][8][9][10]. While many aspects like rotonic excitation spectra [11][12][13][14][15][16][17][18][19], anisotropic superfluidity [20,21], droplet formation [1,6,22], crystallization in 1D [23][24][25][26][27][28], 2D [3,18,19,29,30] and into more exotic patterns [31,32], have been extensively discussed for weakly-dipolar magnetic atoms, systematic studies for molecules, with their much larger and tunable electric dipole moments, have so far remained scarce. Here, we show that Bose-Einstein condensates of ground-state molecules are ideal candidates to further explore the rich phase diagrams of dipolar Bose gases in experiments [33].…”