FisMat2017 - Submission - View

Abstract's title: Finite-temperature phase diagram and critical point of the Aubry pinned sliding transition in a 2D monolayer
Submitting author: Nicola Manini
Affiliation: Dip. di Fisica - Universita` degli Studi di Milano
Affiliation Address: Via Celoria 16 20133 MILANO Italy
Country: Italy
Oral presentation/Poster (Author's request): Oral presentation
Other authors and affiliations: Andrea Silva (Dip. Fisica, Univ. di Milano, Via Celoria 16, 20133 Milano, Italy), Andrea Vanossi (CNR-IOM Democritos National Simulation Center, Via Bonomea 265, 34136 Trieste, Italy), Erio Tosatti (SISSA, Via Bonomea 265, 34136 Trieste, Italy), Roberto Guerra (Dip. Fisica, Univ. di Milano, Via Celoria 16, 20133 Milano, Italy), Davide Mandelli (Tel Aviv University, Tel Aviv 6997801, Israel), Thorsten Brazda (2nd Institute of Physics, University of Stuttgart, Germany), Clemens Bechinger (2nd Institute of Physics, University of Stuttgart, Germany)
Abstract

In a recent experimental breakthrough, the controlled sliding of
two-dimensional colloidal crystals over perfectly regular, laser generated
periodic "corrugation" potentials has been realized [1], providing a novel
opportunity to emulate friction between crystals.  In this context, there
is the unprecedented possibility to study the Aubry superlubric (S) -
pinned (P) transition in two dimensions (2D) when the spacing of the
colloidal lattice and the period of the corrugation are mutually
incommensurate.  Until now, this transition in 2D has only been addressed
theoretically.
As it turns out, real incommensurate 2D lattices come into contact
generally developing, in full equilibrium, a mutual Novaco-McTague
misalignment, conditions in which the existence of a sharp depinning
transition is not trivial.  Simulations [2] have predicted a sharp
Aubry-type transition between an unpinned and a pinned phase as a function
of corrugation.  Unlike 1D, this 2D transition is now of first order, and
remains well defined at T>0.  The transition is heavily structural, with a
local rotation of moire pattern domains from the nonzero initial
Novaco-McTague equilibrium angle to nearly zero [3,4].  In the temperature
(T) -- corrugation strength (W0) plane, the thermodynamical coexistence
line between the S and P phases is strongly oblique, indicating that the S
phase has a larger entropy.  This first-order Aubry line terminates with a
novel critical point T=Tc, marked by a susceptibility peak [5].  The
expected static sliding friction upswing between the S and the P phase
decreases and disappears upon heating from T=0 to T=Tc.  In this
experimental-theoretical effort, we will show the experimental evidence of
the Aubry S-P transition of its frictional implications, and of the added
complexity introduced by the S-P phase coexistence regime in between.


[1] T. Bohlein, J. Mikhael, and C. Bechinger, Nature Mat. 11, 126 (2012).

[2] A. Vanossi, N. Manini, and E. Tosatti, PNAS 109, 16429 (2012).

[3] D. Mandelli, A. Vanossi, N. Manini, E. Tosatti, Phys. Rev. Lett. 114, 108302 (2015).

[4] D. Mandelli, A. Vanossi, M. Invernizzi, S. Paronuzzi, N. Manini, and E. Tosatti,
    Phys. Rev. B 92, 134306 (2015).

[5] D. Mandelli, A. Vanossi, N. Manini, and E. Tosatti, in print in Phys Rev. B.