Cooling molecules in optical cavities

Lu, Weiping; Zhao, Yang; Barker, P. F.

doi:10.1103/physreva.76.013417

Cited by 34 publications

(38 citation statements)

References 14 publications

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“…Equation (6) is consistent with the mean-field approximation [19] and our previous work [20] under the relation mσ 2 0 /2 = k B T /2. Since g ∝ 1/ √ V where V is the cavity mode volume, Eq.…”

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Deceleration of molecules in a supersonic beam by the optical field in a low-finesse cavity

et al. 2010

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We study the dynamics of a supersonic molecular beam in a low-finesse optical cavity and demonstrate that most molecules in the beam can be decelerated to zero central velocity by the intracavity optical field in a process analogous to electrostatic Stark deceleration. We show that the rapid switching of the optical field for slowing the molecules is automatically generated by the cavity-induced dynamics. We further show that ∼ 1% of the molecules can be optically trapped at a few millikelvin in the same cavity.The generation of ultracold molecules is opening up new directions in ultracold physics and chemistry. Ultracold molecules offer the possibility of studying exotic quantum phases through anisotropic electric dipole-dipole interactions [1]. These interactions, however, only become important when they are in the submillikelvin range. The ability to create cold molecules and subsequently trap them in external electric and magnetic fields allows long interaction and interrogation times and therefore high-resolution spectroscopic measurements. Such measurements have already been undertaken with OH radical in the millikelvin temperature range [2], which could be used to constrain the time variation in fine structure constant [3]. Such trapped cold molecules are anticipated to be also important in the search for parity violation [4], and for tests of physics beyond the standard model [5]. Although yet to be explored experimentally, chemistry at ultracold temperatures is dominated by resonance and tunneling phenomena, with reaction rates predicted to be many orders of magnitude larger than at room temperature for some species [6].Cooling of molecules has proven to be considerably more difficult to achieve than laser cooling of atoms [7]. Ultracold molecules can be created from association of laser-cooled atomic species by photoassociation and on magnetic Feshbach resonances at microKelvin temperatures [8]. Recently, progress has been made to transfer these molecules in high vibrational levels to low rovibrational states [9,10]. The methods are, however, limited to atoms that can be laser cooled. Buffer gas cooling is a general method, which can dissipatively cool complex molecular species. This method utilizes elastic collisions within a buffer gas in a cryogenic cell in the 100-mK range [11]. Another technique for creating complex cold molecules is via phase space filtering, in which conservative electrostatic, magnetic, or optical potentials are used to filter out a narrow energy distribution of a hotter gas and then transfer them to zero velocity in the laboratory frame [12][13][14][15][16]. Electrostatic Stark deceleration is a well-developed scheme of this type where gas of 10 6 cm −3 polar molecules in a single quantum state at 10 mK is produced [12]. This scheme uses rapidly switched electrical fields to create a moving potential that traps and slows a subset of the initial molecular distribution. The rate and duration of the switched field change as the trapped molecules are brought to rest. * lanzhihao7@...

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“…1(a). The center-of-mass motion of the molecules in the cavity can be described by the wellestablished semiclassical equations [18][19][20] in one dimension:arXiv:1410.4699v1 [physics.atom-ph] …”

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Deceleration of molecules in a supersonic beam by the optical field in a low-finesse cavity

et al. 2010

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“…Schemes for cooling OH and CN molecules have been suggested [230][231][232] but there are a number of inherent practical challenges. The molecules must be confined within the cavity long enough for appreciable cooling to occur, requiring the design of traps compatible with high-finesse optical cavities, which are typically much smaller than the sources currently used to produce cold molecules.…”

Section: Cavity-assisted Laser Coolingmentioning

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Ultracold molecules and ultracold chemistry

2009

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“…Moreover, optical bistability [31,32], a roton-type softening in the atomic dispersion relation [26,[33][34][35] and optomechanical Bloch oscillations [36] were uncovered. Similar effects occur also for polarizable and thermal particles in a cavity at finite temperature [37][38][39].In this work, motivated by recent experiments [2, 10], we study a hybrid atom-optomechanical setup in the form of a "membrane-in-the-middle" cavity [1,2,[8][9][10][11]], see Fig. 1.…”

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Nonequilibrium Quantum Phase Transition in a Hybrid Atom-Optomechanical System

et al. 2018

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We consider a hybrid quantum many-body system formed by a vibrational mode of a nanomembrane, which interacts optomechanically with light in a cavity, and an ultracold atom gas in the optical lattice of the out-coupled light. The adiabatic elimination of the light field yields an effective Hamiltonian which reveals a competition between the force localizing the atoms and the membrane displacement. At a critical atom-membrane interaction, we find a nonequilibrium quantum phase transition from a localized symmetric state of the atom cloud to a shifted symmetry-broken state, the energy of the lowest collective excitation vanishes, and a strong atom-membrane entanglement arises. The effect occurs when the atoms and the membrane are non-resonantly coupled.Hybrid quantum systems combine complementary fields of physics, such as solid-state physics, quantum optics and atom physics, in one set-up. Recently, a hybrid atom-optomechanical system [1] has been realized experimentally [2] in which a single mechanical mode of a nanomembrane in an optical cavity is optically coupled to a far distant cloud of cold 87 Rb atoms residing in the optical potential of the out-coupled standing wave of the cavity light. When displaced, the membrane experiences the radiation pressure force of the cavity light, and in the bad-cavity limit, the field follows the membrane displacement adiabatically. This modulates the light phase which leads to a shaking of the atom gas in the lattice. The nanomechanical motion of the membrane then couples non-resonantly to the collective motion of the atoms. The aim is twofold [1][2][3][4][5][6][7]: The gas can cool the nanomembrane, and, emergent phenomena of the correlated quantum many-body system are of interest [8][9][10][11][12][13][14][15][16][17].State-of-the-art optomechanics [3-6] is nowadays able to realize optical feedback cooling [18,19] of the mechanical oscillator to its quantum-mechanical ground state [20,21]. Yet, the resolved sideband limit allows ground-state cooling only if the oscillator frequency exceeds the photon loss rate in the cavity [22][23][24]. Hence, cooling a macroscopic low-frequency nanomembrane close to its ground state is so far not possible. One promising alternative [1,7] is to utilize an ultracold atom gas, which has been demonstrated recently [2] by sympathetic cooling down to 650 mK. Current investigations aim to a coherent state transfer of robust quantum entanglement [15].Apart from cooling the nanomembrane, an interesting fundamental feature is the collective quantum-many body behavior of the hybrid system. For instance, the atom-atom interaction can in principle be coherently modulated by the back-action of the cavity light on the nanooscillator. By this, a long-range interaction emerges which resembles that of a dipolar Bose-Einstein condensate (BEC) [25]. In fact, a simpler hybrid quantum many-body system has also been implemented in the form of a BEC in an optical lattice inside a transversely pumped optical cavity. A Dicke quantum phase transition between a n...

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Cooling molecules in optical cavities

Cited by 34 publications

References 14 publications

Deceleration of molecules in a supersonic beam by the optical field in a low-finesse cavity

Deceleration of molecules in a supersonic beam by the optical field in a low-finesse cavity

Ultracold molecules and ultracold chemistry

Nonequilibrium Quantum Phase Transition in a Hybrid Atom-Optomechanical System

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