DQMP Forum - Quench Dynamics of Coupled Luttinger Liquids - NMR Studies of the Perovskite Rare-earth Nickelates

16.03.2021 13:00 – 14:30

Quench Dynamics of Coupled Luttinger Liquids
Paola Ruggiero (group of prof. Giamarchi)

Quantum systems in low-dimensions are special in that the effects of strong correlations and interactions are enhanced and lead to dramatic effects. A celebrated example from condensed matter physics is the breakdown of Landau’s Fermi liquid theory in 1D, which is replaced by the Luttinger liquid (LL) paradigm. The latter has been largely employed to study both equilibrium and out-of-equilibrium problems, with particular reference in more recent times to the dynamics generated after a quantum quench protocol. In this last case, while a lot is known for a single LL, less is known when two (or more) of them are coupled: this situation is relevant, for example, for the quench dynamics in the Hubbard model, or in tunnel-coupled tubes in cold atoms experiments.
This problem was initially studied under the assumption for the two LLs to be identical, which leads to major simplifications. Recently, instead, a couple of works considered the quench dy-namics of two different LL, aiming at understanding the effect of the imbalance between them. In our contributions, the problem was solved at first relying on semiclassical approximation [1]. This approximation gives access already to a very rich phenomenology,with (i) the emergence of multiple light cones, separating different decaying regimes; (ii) a prethermal regime even-tually decaying into a quasi-thermal one; (iii) non-trivial effects of a non-zero temperature in the initial state. We then extended such results to more general situations relying on Conformal Fiel Theory methods


NMR Studies of the Perovskite Rare-earth Nickelates
Lukas Korosec (group of prof. Triscone)

The perovskite rare-earth nickelates (RE NiO3) are complex oxide materials that are well-known for their strongly-correlated electron physics. Their phase diagram contains paramagnetic metallic, paramagnetic insulating, and antiferromagnetic insulating phases. In the insulating phases, a structural modulation by alternating large and small NiO6 octahedra is observed, which has often been interpreted as an effect of a charge disproportionation. Antiferromagnetic order occurs at the unusual wavevector (1/4, 1/4, 1/4)pc, with four Ni sites per period. Nuclear magnetic resonance (NMR) spectroscopy in 17O-enriched samples has offered a new experimental perspective on these materials the nuclear electric quadrupole moment can act as a probe for charge disproportionation n this system. Nuclear spin relaxation has allowed us to study the magnetic dynamics of the antiferromagnetic state, the role of magnetic fluctuations in the phase transitions of RE NiO3, and the nature of the metallic phase.

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