scholarly journals Observing multifarious topological phase transitions with real-space indicator

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Yong-Heng Lu ◽  
Yao Wang ◽  
Feng Mei ◽  
Yi-Jun Chang ◽  
Hang Zheng ◽  
...  

Abstract First- and second-order topological phases, capable of inherent protection against disorder of materials, have been recently experimentally demonstrated in various artificial materials through observing the topologically protected edge states. Topological phase transition represents a new class of quantum critical phenomena, which is accompanied by the changes related to the bulk topology of energy band structures instead of symmetry. However, it is still a challenge to directly observe the topological phase transitions defined in terms of bulk states. Here, we theoretically and experimentally demonstrate the direct observation of multifarious topological phase transitions with real-space indicator in a single photonic chip, which is formed by integration of 324 × 33 waveguides supporting both first- and second-order topological phases. The trivial-to-first-order, trivial-to-second-order and first-to-second-order topological phase transitions signified by the band gap closure can all be directly detected via photon evolution in the bulk. We further observe the creation and destruction of gapped topological edge states associated with these topological phase transitions. The bulk-state-based route to investigate the high-dimensional and high-order topological features, together with the platform of freely engineering topological materials by three-dimensional laser direct writing in a single photonic chip, opens up a new avenue to explore the mechanisms and applications of artificial devices.

2017 ◽  
Vol 19 (43) ◽  
pp. 29647-29652 ◽  
Author(s):  
Yi-zhen Jia ◽  
Wei-xiao Ji ◽  
Chang-wen Zhang ◽  
Ping Li ◽  
Shu-feng Zhang ◽  
...  

Topological phases, especially topological crystalline insulators (TCIs), have been intensively explored and observed experimentally in three-dimensional (3D) materials.


2020 ◽  
Author(s):  
Chunyin Qiu ◽  
Huahui Qiu ◽  
Meng Xiao ◽  
Fan Zhang

Abstract Discovering new topological phases of matter is a major theme in fundamental physics and materials science1,2. Dirac semimetal features isolated fourfold linear band crossings, i.e., Dirac points, and provides an exceptional platform for exploring topological phase transitions under symmetry breaking3. Recent theoretical studies4,5 have revealed that a three-dimensional Dirac semimetal can harbor fascinating hinge states, a high-order (HO) topological manifestation not known before. However, realization of such a HO Dirac phase in experiment is yet to be achieved, not to mention the fascinating hinge states, although candidate solid-state materials have been suggested5. Here we propose a minimum model to construct a spinless HO Dirac semimetal protected by C_6v symmetry. By breaking different symmetries, this parent phase transitions into a variety of novel topological phases including HO topological insulator, HO Weyl semimetal, and HO nodal-ring semimetal. Furthermore, for the first time, we experimentally realize this unprecedented HO topological phase in a sonic crystal and unambiguously present the smoking-gun observation of the desired hinge states via momentun-space spectroscopy and real-space visualization. Our findings may offer new opportunities to manipulate classical waves such as sound and light.


Small ◽  
2017 ◽  
Vol 13 (11) ◽  
pp. 1603190 ◽  
Author(s):  
Sergey Kruk ◽  
Alexey Slobozhanyuk ◽  
Denitza Denkova ◽  
Alexander Poddubny ◽  
Ivan Kravchenko ◽  
...  

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