09:00  12:00

informal discussions (onsite & in gather.town)

12:30  13:20

Lunch


Chair: Maksym Serbyn

13:30  14:10

Konstantin Tikhonov
(Skoltech)
Manybody localization in quantum dot models and Anderson localization on random graphs (virtual)

14:10  14:35

Ivan Khaymovich
(MPIPKS Dresden)
Randommatrix approach to slow dynamics in quantum systems
In this talk, we will discuss a randommatrix approach to the description of disordered manybody systems and their Hilbertspace structure, mostly focusing on the slow dynamics in such models.
As a generic example of this approach, we consider the static and the dynamical phases in a RosenzweigPorter random matrix ensemble with a distribution of offdiagonal matrix elements of the form of the largedeviation ansatz.
We present a general theory of survival probability in such a randommatrix model and show that the averaged survival probability may decay with time as a simple exponent, as a stretchexponent and as a powerlaw or slower. Correspondingly, we identify the exponential, the stretchexponential and the frozendynamics phases.
We consider the mapping of the Anderson localization model on Random Regular Graph, the known proxy of MBL, onto the RP model and find exact values of the stretchexponent kappa in the thermodynamic limit.
Our theory allows to describe analytically the finitesize multifractality and to compute the critical length with the exponent 1 associated with it.
Corresponding publication:
I. M. Khaymovich and V. E. Kravtsov "Dynamical phases in a "multifractal" RosenzweigPorter model" [arxiv:2106.01965]

14:35  15:00

Henning Schomerus
(Lancaster University)
Fock space and random matrix perspective on ergodicitybreaking manybody states
I combine a geometric perspective on Fock space with considerations from randommatrix theory to provide insights into quantum systems that obey an area law on entanglement induced by disorder or measurements.
For instance, individual manybodylocalized eigenstates are well approximated by a Slater determinant of singleparticle orbitals, but the orbitals of different eigenstates in a given system display an imperfect degree of compatibility, close to that of completely random states. Such considerations also illuminate the strongly dressed nature of any emergent local conserved quantities, as well as the universal properties of such systems.
Universality of Entanglement Transitions from Stroboscopic to Continuous Measurements
M. Szyniszewski, A. Romito, and H. Schomerus, Phys. Rev. Lett. 125, 210602 (2020).
Fockspace geometry and strong correlations in manybody localized systems
Christian P. Chen and Henning Schomerus,
arXiv:2107.05502 [condmat.disnn]. (2021)
Randommatrix perspective on manybody entanglement with a finite localization length
Marcin Szyniszewski and Henning Schomerus,
Phys. Rev. Research 2, 032010(R) (2020).
Entanglement transition from variablestrength weak measurements
M. Szyniszewski, A. Romito, and H. Schomerus,
Phys. Rev. B 100, 064204 (2019).

15:00  15:25

KenIchiro Imura
(Hiroshima University)
Unusual diffusion and entanglement dynamics in disordered nonHermitian systems (virtual)
Taking the HatanoNelson model as a concrete example, we first consider how diffusion occurs in a nonHermitian disordered system,
and show that it is very different from the Hermitian case. Interestingly, a cascade like diffusion process of an initial wave packet as in the Hermitian case is suppressed in the clean limit and at weak disorder, while it revives in the vicinity the localizationdelocalization transition. Based on this observation, we then analyze how the entanglement entropy of the system evolves in time in the interacting nonHermitian model, revealing its nonmonotonic evolution in time. We clarify the different roles of dephasing in the time evolution of entanglement entropy.

15:25  16:15

Coffee break


Chair: Vedika Khemani

16:15  16:55

Dragana Popovic
(The National High Magnetic Field Laboratory)
Screening the Coulomb interaction leads to a prethermal regime in twodimensional bad conductors (virtual)
The absence of thermalization in certain isolated manybody systems is of great fundamental interest and potential technological importance. However, it is not well understood how the interplay of disorder and interactions affects thermalization, especially in two dimensions (2D), and experiments on solidstate materials remain scarce. We report on the study of nonequilibrium dynamics exhibited after a rapid change of electron density $n_\mathrm{s}$, in two sets of disordered 2D electron systems in Si, poorly coupled to a thermal bath. In the low conductivity regime at low $n_\mathrm{s}$, we find that, while the dynamics is glassy in devices with the longrange Coulomb interaction, in the case of screened Coulomb interaction the thermalization is anomalously slow, consistent with the proximity to a manybodylocalized (MBL) phase, i.e. the MBLlike, prethermal regime. Our results demonstrate that the MBL phase in a 2D electron system can be approached by tuning the interaction range, thus paving the way to further studies of the breakdown of thermalization and MBL in real materials.

16:55  17:35

Jens H. Bardarson
(KTH Royal Institute of Technology)
Timeevolution of local information: thermalization dynamics of local observables (virtual)

17:35  18:15

William Morong
(University of Maryland, College Park)
Quantum simulations of nonthermal phenomena with trapped ions
Recent years have seen the development of isolated quantum simulator platforms capable of exploring interesting questions at the frontiers of manybody physics. We describe our platform, based on a chain of Ytterbium ions in a linear trap, and describe its capabilities, which include longrange spinspin interactions and singlesite manipulation and readout. We then describe some recent studies undertaken with this machine, focusing on two. The first is the observation of domainwall confinement, in which the longrange interactions cause individual domain walls to become bound into mesonlike quasiparticles. The second, observation of Stark manybody localization, in which a linearly increasing gradient halts thermalization in favor of a state similar to disorderinduced manybody localization. These results show some of the richness possible in nonthermalizing behavior, and we discuss possible relations between them and recently studied mechanisms for breaking ergodicity such as Hilbert space fragmentation.

18:15  19:30

Dinner


Chair: Romain Vasseur

19:30  20:10

Ehud Altman
(University of California, Berkeley)
Critical behavior near the manybody localization transition in driven open systems (virtual)

20:10  20:35

Andrea De Luca
(CNRS)
Spectral form factor in extended translational invariant systems (virtual)
We introduce a class of unitary circuits which are invariant under translations. In the limit of large local Hilbert space dimensions, we compute explicitly the spectral form factor, characterizing the spectral correlation of the model. We show that at time larger than the Thouless time, the random matrix behavior is recovered. Additionally, we identify a scaling function which characterize an extended transient regime towards the random matrix prediction. Compared with the inhomogeneous system, we identify logarithmic corrections which are the direct consequence of translation invariance. We discuss the generalization of these results to arbitrary chaotic model which have a translation symmetry.

20:35  21:00

Sergey Syzranov
(University of California, Santa Cruz)
Equivalence of interacting semimetals and lowdensity manybody systems to singleparticle systems with quenched disorder (virtual)
We demonstrate that a broad class of interacting disorderfree systems, such as nodal semimetals (e.g. graphene, Weyl, nodalline semimetals) and dilute interacting gases, can be mapped to noninteracting systems with quenched disorder. The interacting systems that allow for such a mapping include systems with a small singleparticle density of states at the chemical potential (e.g. near a nodal point or a nodal line in a topological semimetal), which leads to a suppressed screening of the interactions. The established duality suggests a new approach for analytical and numerical studies of manybody phenomena in a class of interacting disorderfree systems by reducing them to singleparticle problems. It allows one to predict, describe and classify manybody phenomena by mapping them to the effects known for disordered noninteracting systems. We illustrate the mapping by showing that clean semimetals with attractive interactions exhibit interactiondriven transitions at low temperatures in the same universality classes as the nonAnderson disorderdriven transitions predicted in highdimensional noninteracting semimetals. Furthermore, we find a new nonAnderson disorderdriven transition dual to a previously known interactiondriven transition in clean bosonic gases. The established principle may also be used to classify and describe phase transitions in dissipative systems described by nonHermitian Hamiltonians.

21:00  21:15

Closing
