Date(s) - 20/06/2017
13h00 - 14h30
Controlling the Intrinsic Polarization State in RF Sputtering Grown Ferroelectric Ultrathin Films Christian Weymann (group of Prof. Paruch & Triscone)
Ferroelectric ultrathin films are a technologically important field of study, proposed as potential memory devices, memristors, or as a platform for novel integrated electronics using domain wall conduction. Crucial to all of these applications is the intrinsic polarization state of the thin film.
We show that we can manipulate this intrinsic polarization state by acting on the electrostatic boundary conditions via the use of dielectric spacer layers to increase the depolarizing field1,2, or modulating the built-in field through changes in the growth temperature of PbTiO3 thin films, allowing full control over the intrinsic polarization state (monodomain up vs. polydomain vs. monodomain down).
1 Tuning of the depolarization field and nanodomain structure in ferroelectric thin films, C. Lichtensteiger et al., Nano Letters 14(8) 42025 (2014)
2 Built-in voltage in thin ferroelectric PbTiO3 films: the effect of electrostatic boundary conditions, C. Lichtensteiger et al., New Journal of Physics 18 043030 (2016)
Exponential Lifetime Improvement in Topological Quantum Memories Charles Bardyn (group of Prof. Giamarchi)
I will present a simple yet efficient mechanism for passive error correction in topological quantum memories.
The scheme relies on driven-dissipative ancilla systems which couple to local excitations (anyons) and make them “sink” in energy, with no required interaction among ancillae or anyons. Through this process, anyons created by some thermal environment end up trapped in potential “trenches” that they themselves generate, which can be interpreted as a “memory foam” for anyons. This self-trapping mechanism provides an energy barrier for anyon propagation, and removes entropy from the memory by favoring anyon recombination over anyon separation (responsible for memory errors). We demonstrate that our scheme leads to an exponential increase of the memory-coherence time with system size L, up to an upper bound Lmax which can increase exponentially with Δ/T, where T is the temperature and Δ is some energy scale defined by potential trenches. This results in a double exponential increase of the memory time with Δ/T, which greatly improves over the Arrhenius (single-exponential) scaling found in typical quantum memories.
Forum Committee : C.Lichtensteiger, A.Tamai, N.Ubrig (14.06.2017)