Structural Properties of Two-Component Coulomb Crystals in Linear Paul Traps

Abstract

We report on structural properties of two-component Coulomb crystals in a linear Paul trap. The crystals consist of two laser cooled ion species, 24Mg+ and 40Ca+. The lighter 24Mg+ ions form an inner cylindrical crystal structure surprisingly similar to that of an infinitely long single component crystal, while the outermost shell of the surrounding 40Ca+ ions have a spheroidal shape, which is highly insensitive to the presence of the 24Mg+ ions. Observed changes in the radial separation of the two ion species with the radius of the inner cylindrical crystal is explained by a simple model.

Fast and efficient transport of large ion clouds

“…To valid our fit procedure, for the same ion cloud, simply deformed by changing the trapping parameters, we use the two calculated semi-axis lengths R e and L e to estimate the ellipse aspect ratio ρ e = R e /L e and volume V e = 4πR 2 e L e /3 extracted from experimental data. We can compare the aspect ratio with the expected one, deduced from the effective pseudo-potential ρ = f (ω z /ω r ) by an equation demonstrated in [28] and experimentally confirmed in [30]. More precisely, we measure the relative shift δ L between the length deduced from the fit and the one deduced by the fitted radius, assuming a known aspect ratio : δ L = (L e − R e /ρ)/L e .…”

Optically induced structural phase transitions in ion Coulomb crystals

“…For medium sized crystals often employed in experiments [26, 27] (∼ 10 3 − 10 5 ions), the structure is generally not very stable, and thermally induced transitions between a large variety of states including metastable bcc and fcc structures and incommensurable crystallite formations can be observed [40,41]. While structural stability can be dramatically increased using two-species crystals [21,23], means to control and manipulate the structures of single-species crystals are highly wanted, not only for applications in quantum information science, but also for exploiting Coulomb crys- In this Letter, we report on molecular dynamics (MD) simulations of harmonically trapped ion Coulomb crystals in the presence of an additional periodically corrugated potential in the form of an induced dipole potential originating from a far off-resonant standing-wave light field [44]. We demonstrate how such a potential can be exploited to prevent thermally induced crystal phase transitions and/or to induce controlled and efficient transitions between bcc and fcc crystal structures.…”

“…For medium sized crystals often employed in experiments [26,27] (∼ 10 3 − 10 5 ions), the structure is generally not very stable, and thermally induced transitions between a large variety of states including metastable bcc and fcc structures and incommensurable crystallite formations can be observed [40,41]. While structural stability can be dramatically increased using two-species crystals [21,23], means to control and manipulate the structures of single-species crystals are highly wanted, not only for applications in quantum information science, but also for exploiting Coulomb crystals as simulators of solid state physics, like structural transitions of iron under extreme pressure [42] of relevance for geophysics and thin-film growth [43] of importance for nanotechnology.…”

“…Ty, 37.10.Vz, 64.70.kp, 36.40.Ei When an ensemble of confined ions with the same sign of charge is cooled to a sufficiently low temperature, the ionic system forms a crystalline structure [1], often referred to as an ion Coulomb crystal. Since the first experimental realizations of ion Coulomb crystals through laser cooling of atomic ions into the milli-Kelvin regime in electromagnetic traps [2,3], there has been growing theoretical [4][5][6][7][8][9][10][11][12][13][14] and experimental [15][16][17][18][19][20][21][22][23][24] interest in studying the structural and dynamic properties of these crystals under different trapping conditions and for various ion compositions.The unique localization and isolation of the individual ions constituting the crystals have already led to a large number of amazing results within precision measurements [25], cavity quantum electrodynamics (CQED) [26][27][28][29][30], quantum information science [31][32][33][34][35], and cold molecular science [36][37][38][39]. For experiments involving larger three-dimensional ion Coulomb crystals, such as CQED related experiments [26,27] with the interesting prospect of creating quantum memories and other quantum devices, ...…”

“…Ty, 37.10.Vz, 64.70.kp, 36.40.Ei When an ensemble of confined ions with the same sign of charge is cooled to a sufficiently low temperature, the ionic system forms a crystalline structure [1], often referred to as an ion Coulomb crystal. Since the first experimental realizations of ion Coulomb crystals through laser cooling of atomic ions into the milli-Kelvin regime in electromagnetic traps [2,3], there has been growing theoretical [4][5][6][7][8][9][10][11][12][13][14] and experimental [15][16][17][18][19][20][21][22][23][24] interest in studying the structural and dynamic properties of these crystals under different trapping conditions and for various ion compositions.…”