English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Defects are believed to play a fundamental role in the supersolid state of4He. We have studied solid 4He in two dimensions (2D) as function of the numberof vacancies n_v, up to 30, inserted in the initial configuration at rho =0.0765 A^-2, close to the melting density, with the exact zero temperatureShadow Path Integral Ground State method. The crystalline order is found to bestable also in presence of many vacancies and we observe two completelydifferent regimes. For small n_v, up to about 6, vacancies form a bound stateand cause a decrease of the crystalline order. At larger n_v, the formationenergy of an extra vacancy at fixed density decreases by one order of magnitudeto about 0.6 K. In the equilibrated state it is no more possible to recognizevacancies because they mainly transform into quantum dislocations andcrystalline order is found almost independent on how many vacancies have beeninserted in the initial configuration. The one--body density matrix in thislatter regime shows a non decaying large distance tail: dislocations, that in2D are point defects, turn out to be mobile, their number is fluctuating, andthey are able to induce exchanges of particles across the system mainlytriggered by the dislocation cores. These results indicate that the notion ofincommensurate versus commensurate state loses meaning for solid 4He in 2D,because the number of lattice sites becomes ill defined when the system is notcommensurate. Crystalline order is found to be stable also in 3D in presence ofup to 100 vacancies.

Quantum dislocations: the fate of multiple vacancies in two dimensional solid 4He