208 research outputs found
Non-Abelian inverse Anderson transitions
Inverse Anderson transitions, where the flat-band localization is destroyed
by disorder, have been wildly investigated in quantum and classical systems in
the presence of Abelian gauge fields. Here, we report the first investigation
on inverse Anderson transitions in the system with non-Abelian gauge fields. It
is found that pseudospin-dependent localized and delocalized eigenstates
coexist in the disordered non-Abelian Aharonov-Bohm cage, making inverse
Anderson transitions depend on the relative phase of two internal pseudospins.
Such an exotic phenomenon induced by the interplay between non-Abelian gauge
fields and disorder has no Abelian analogy. Furthermore, we theoretically
design and experimentally fabricate nonAbelian Aharonov-Bohm topolectrical
circuits to observe the non-Abelian inverse Anderson transition. Through the
direct measurements of frequency-dependent impedance responses and voltage
dynamics, the pseudospin-dependent non-Abelian inverse Anderson transitions are
observed. Our results establish the connection between inverse Anderson
transitions and non-Abelian gauge fields, and thus comprise a new insight on
the fundamental aspects of localization in disordered non-Abelian flat-band
systems
Observation of inverse Anderson transitions in Aharonov-Bohm topolectrical circuits
It is well known that Anderson transition is a disorder-induced
metal-insulator transition.Contrary to this conventional wisdom, some
investigations have shown that disorders could destroy the phase coherence of
localized modes in flatbands, making the localized states melt into extended
states. This phenomenon is called the inverse Anderson transition. While, to
date, the experimental observation of inverse Anderson transitions is still
lacking. In this work, we report the implementation of inverse Anderson
transitions based on Aharonov-Bohm topolectrical circuits. Different types of
disorders, including symmetric-correlated, antisymmetric-correlated and
uncorrelated disorders, can be easily implemented in Aharonov-Bohm circuits by
engineering the spatial distribution of ground settings. Through the direct
measurements of frequency-dependent impedance responses and time-domain voltage
dynamics, the inverse Anderson transitions induced by antisymmetric-correlated
disorders are clearly observed. Moreover, the flat bands and associated spatial
localizations are also fulfilled in clean Aharonov-Bohm circuits or
Aharonov-Bohm circuits sustaining symmetric-correlated and uncorrelated
disorders, respectively. Our proposal provides a flexible platform to
investigate the interplay between the geometric localization and Anderson
localization, and could have potential applications in electronic signal
control.Comment: 12 pages, 4 figure
Exploring topological phase transition andWeyl physics in five dimensions with electric circuits
Weyl semimetals are phases of matter with gapless electronic excitations that
are protected by topology and symmetry. Their properties depend on the
dimensions of the systems. It has been theoretically demonstrated that
five-dimensional (5D) Weyl semimetals emerge as novel phases during the
topological phase transition in analogy to the three-dimensional case. However,
experimental observation of such a phenomenon remains a great challenge because
the tunable 5D system is extremely hard to construct in real space. Here, we
construct 5D electric circuit platforms in fully real space and experimentally
observe topological phase transitions in five dimensions. Not only are Yang
monopoles and linked Weyl surfaces observed experimentally, but various phase
transitions in five dimensions are also proved, such as the phase transitions
from a normal insulator to a Hopf link of twoWeyl surfaces and then to a 5D
topological insulator. The demonstrated topological phase transitions in five
dimensions leverage the concept of higher-dimensional Weyl physics to control
electrical signals in the engineered circuits
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