اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدDisordered insulator in an optical lattice
119
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Disorder can profoundly affect the transport properties of a wide range of quantum materials. Presently, there is significant disagreement regarding the effect of disorder on transport in the disordered Bose-Hubbard (DBH) model, which is the paradigm used to theoretically study disorder in strongly correlated bosonic systems. We experimentally realize the DBH model by using optical speckle to introduce precisely known, controllable, and fine-grained disorder to an optical lattice5. Here, by measuring the dissipation strength for transport, we discover a disorder-induced SF-to-insulator (IN) transition in this system, but we find no evidence for an IN-to-SF transition. Emergence of the IN at disorder strengths several hundred times the tunnelling energy agrees with a predicted SF--Bose glass (BG) transition from recent quantum Monte Carlo (QMC) work. Both the SF--IN transition and correlated changes in the atomic quasimomentum distribution--which verify a simple model for the interplay of disorder and interactions in this system--are phenomena new to the unit filling regime explored in this work, compared with the high filling limit probed previously. We find that increasing disorder strength generically leads to greater dissipation in the regime of mixed SF and Mott-insulator (MI) phases, excluding predictions of a disorder-induced, or re-entrant, SF (RSF). While the absence of an RSF may be explained by the effect of finite temperature, we strongly constrain theories by measuring bounds on the entropy per particle in the disordered lattice.
قيم البحث
اقرأ أيضاً
Topology and disorder have deep connections and a rich combined influence on quantum transport. In order to probe these connections, we synthesized one-dimensional chiral symmetric wires with controllable disorder via spectroscopic Hamiltonian engine
ering, based on the laser-driven coupling of discrete momentum states of ultracold atoms. We characterize the systems topology through measurement of the mean chiral displacement of the bulk density extracted from quench dynamics. We find evidence for the topological Anderson insulator phase, in which the band structure of an otherwise trivial wire is driven topological by the presence of added disorder. In addition, we observed the robustness of topological wires to weak disorder and measured the transition to a trivial phase in the presence of strong disorder. Atomic interactions in this quantum simulation platform will enable future realizations of strongly interacting topological fluids.
One of the most important issues in disordered systems is the interplay of the disorder and repulsive interactions. Several recent experimental advances on this topic have been made with ultracold atoms, in particular the observation of Anderson loca
lization, and the realization of the disordered Bose-Hubbard model. There are however still questions as to how to differentiate the complex insulating phases resulting from this interplay, and how to measure the size of the superfluid fragments that these phases entail. It has been suggested that the correlation function of such a system can give new insights, but so far little experimental investigation has been performed. Here, we show the first experimental analysis of the correlation function for a weakly interacting, bosonic system in a quasiperiodic lattice. We observe an increase in the correlation length as well as a change in shape of the correlation function in the delocalization crossover from Anderson glass to coherent, extended state. In between, the experiment indicates the formation of progressively larger coherent fragments, consistent with a fragmented BEC, or Bose glass.
We propose a model to realize a fermionic superfluid state in an optical lattice circumventing the cooling problem. Our proposal exploits the idea of tuning the interaction in a characteristically low entropy state, a band-insulator in an optical bil
ayer system, to obtain a superfluid. By performing a detailed analysis of the model including fluctuations and augmented by a variational quantum Monte Carlo calculations of the ground state, we show that the superfluid state obtained has high transition temperature of the order of the hopping energy. Our system is designed to suppress other competing orders such as a charge density wave. We suggest a laboratory realization of this model via an orthogonally shaken optical lattice bilayer.
We propose a realization of the one-dimensional random dimer model and certain N-leg generalizations using cold atoms in an optical lattice. We show that these models exhibit multiple delocalization energies that depend strongly on the symmetry prope
rties of the corresponding Hamiltonian and we provide analytical and numerical results for the localization length as a function of energy. We demonstrate that the N-leg systems possess similarities with their 1D ancestors but are demonstrably distinct. The existence of critical delocalization energies leads to dips in the momentum distribution which serve as a clear signal of the localization-delocalization transition. These momentum distributions are different for models with different group symmetries and are identical for those with the same symmetry.
Quasicrystals are long-range ordered but not periodic, representing an interesting middle ground between order and disorder. We experimentally and numerically study the ground state of non- and weakly-interacting bosons in an eightfold symmetric quas
icrystalline optical lattice. We find extended states for weak lattices but observe a localisation transition at a lattice depth of $V_0=1.78(2),E_{mathrm{rec}}$ for the non-interacting system. We identify this transition by measuring the timescale required for adiabatic loading into the lattice, which diverges at the critical lattice depth for localisation. Gross-Pitaevskii simulations show that in interacting systems the transition is shifted to deeper lattices, as expected from superfluid order counteracting localisation. Our experimental results are consistent with such a mean-field shift. Quasiperiodic potentials, lacking conventional rare regions, provide the ideal testing ground to realise many-body localisation in 2D.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
