Floquet higher-order **topological** **insulators** and superconductors with
space-time symmetries

**topological**

**insulators**and superconductors (HOTI/SCs) with an order-two space-time symmetry or antisymmetry are classified. This is achieved by considering unitary loops, whose nontrivial topology leads to the anomalous Floquet

**topological**phases, subject to a space-time symmetry/antisymmetry. By mapping these unitary loops to static Hamiltonians with an order-two crystalline symmetry/antisymmetry, one is able to obtain the $K$ groups for the unitary loops and thus complete the classification of Floquet HOTI/SCs. Interestingly, we found that for every order-two nontrivial space-time symmetry/antisymmetry involving a half-period time translation, there exists a unique order-two static crystalline symmetry/antisymmetry, such that the two symmetries/antisymmetries give rise to the same

**topological**classification. Moreover, by exploiting the frequency-domain formulation of the Floquet problem, a general recipe that constructs model Hamiltonians for Floquet HOTI/SCs is provided, which can be used to understand the classification of Floquet HOTI/SCs from an intuitive and complimentary perspective.

10/10 relevant

arXiv

Quantum anomalous Hall effect in two dimensional Janus Mn2Cl3Br3 with large magnetic anisotropy energy

**topological**

**insulators**. Expand abstract.

**topological**

**insulators**. However, the QAH effect only at extremely low temperatures due to the weak magnetic coupling, small band gap and low carrier mobility. Here, based on first-principles density functional theory, we predict that the Janus Mn2Cl3Br3 is high Curie temperature ferromagnet that host the QAH phase. Furthermore, we find that it is a Dirac half-metal characterized by a Dirac cone in one spin channel with carrier mobilities comparable to freestanding germanene and an large band gap in other spin channel. Simultaneously, when the spin-orbital coupling interaction is considered, the Janus Mn2Cl3Br3 exhibit lager magnetic anisotropic energy of 11.89 meV/cell and a nontrivial band gap. More interestingly, both the Chern number sign and the chiral edge current are tuned by changing the direction of magnetization. Our finding would suggest the possibility of not only realized the QAH effect but also designed the flow direction of the edge current.

4/10 relevant

arXiv

Anomalous localization at the boundary of an interacting **topological**
**insulator**

**topological**

**insulator**(TI) hosts an anomaly restricting its possible phases: e.g. 3D strong and weak TIs maintain surface conductivity at any disorder if symmetry is preserved on-average, at least when electron interactions on the surface are weak. Expand abstract.

**topological**

**insulator**(TI) hosts an anomaly restricting its possible phases: e.g. 3D strong and weak TIs maintain surface conductivity at any disorder if symmetry is preserved on-average, at least when electron interactions on the surface are weak. However the interplay of strong interactions and disorder with the boundary anomaly has not yet been theoretically addressed. Here we study this combination for the edge of a 2D TI and the surface of a 3D weak TI, showing how it can lead to an "Anomalous Many Body Localized" (AMBL) phase that preserves the anomaly. We discuss how the anomalous Kramers parity switching with pi flux arises in the bosonized theory of the localized helical state. The anomaly can be probed in localized boundaries by electrostatically sensing nonlinear hopping transport with e/2 shot noise. Our AMBL construction in 3D weak TIs fails for 3D strong TIs, suggesting that their anomaly restrictions are distinguished by strong interactions.

7/10 relevant

arXiv

Multipolar **Topological** Field Theories: Bridging Higher Order **Topologic**al
**Insulators** and Fractons

**topological**phases, namely fractons and higher order

**topological**

**insulators**(HOTIs), share at least superficial similarities. The wide variety of proposals for these phases calls for a universal field theory description that captures their key characteristic physical phenomena. In this work, we construct

**topological**multipolar response theories that capture the essential features of some classes of fractons and higher order

**topological**

**insulators**. Remarkably, we find that despite their distinct symmetry structure, some classes of fractons and HOTIs can be connected through their essentially identical

**topological**response theories. More precisely, we propose a

**topological**quadrupole response theory that describes both a 2D symmetry enriched fracton phase and a related bosonic quadrupolar HOTI with strong interactions. Such a

**topological**quadrupole term encapsulates the protected corner charge modes and, for the HOTI, predicts an anomalous edge with fractional dipole moment. In 3D we propose a dipolar Chern-Simons theory with a quantized coefficient as a description of the response of both second order HOTIs harboring chiral hinge currents, and of a related fracton phase. This theory correctly predicts chiral currents on the hinges and anomalous dipole currents on the surfaces. We generalize these results to higher dimensions to reveal a family of multipolar Chern-Simons terms and related $\theta$-term actions that can be reached via dimensional reduction or extension from the Chern-Simons theories.

10/10 relevant

arXiv

Elastic higher-order **topological** **insulators** with quantization of the
quadrupole moments

**topological**edge states and zero-dimensional (0D)

**topologic**al corner states are visualized and can be transformed each other by tuning the crystalline symmetry in a hierarchical structure. Expand abstract.

**topological**edge states and zero-dimensional (0D)

**topological**corner states are visualized and can be transformed each other by tuning the crystalline symmetry in a hierarchical structure. The systematic band structure calculations indicate that elastic wave energy in the hierarchical structure can be localized with remarkable robustness, which is very promising for new generations of integrated solid-state phononic circuits with a great versatility.

8/10 relevant

arXiv

Flux Free Single Crystal Growth and Detailed Physical Property
Characterization of Bi1-xSbx (x = 0.05, 0.1 and 0.15) **Topological** **Insulator**

**topological**

**insulators**and their technological applications. Expand abstract.

**topological**

**insulator**. Single crystals of Bi1-xSbx (x = 0.05, 0.1 and 0.15) were grown by melting bismuth and antimony together using the facile self flux method. The XRD measurements displayed highly indexed 00l lines and confirmed the crystalline nature as well as the rhombohedral structure of the Bi1-xSbx (x = 0.05, 0.1 and 0.15) crystals. Raman spectroscopy measurements for Bi1-xSbx system revealed four peaks within the spectral range of 10 to 250 cm-1 namely A1g and Eg modes corresponding to Bi-Bi and Sb-Sb vibrations. Scanning electron microscopy (SEM) and energy dispersive Temperature dependent electrical resistivity curves with and without applied magnetic field exhibited a metallic behaviour and linear non-saturating magneto-resistance (MR) respectively for all the antimony (Sb) concentrations of x = 0.05, 0.1 and 0.15. The lowest Sb concentration sample with x = 0.05 (Bi0.95Sb0.05) exhibited the highest MR value of about 1400%, followed by x = 0.1 and 0.15 samples (Bi0.9Sb0.1 and Bi0.85Sb0.05) with MR values reaching up to 500% and 110% respectively at 2K and 6Tesla applied field. The magneto-conductivity (MC) is fitted to the HLN (Hikami Larkin Nagaoka) equation and it is found that the charge conduction mechanism is mainly dominated by WAL (weak anti-localization) along with a small contribution from WL (weak localization) effect. Summarily, the short letter discusses the synthesis, interesting transport and magneto-transport properties of Bi1-xSbx (x = 0.05, 0.1 and 0.15), which could be useful in understanding the fascinating properties of

**topological**

**insulators**and their technological applications.

10/10 relevant

arXiv

Odd-frequency superconductivity and Meissner effect in the doped
**topological** **insulator** Bi$_2$Se$_3$

5/10 relevant

arXiv

Theoretical investigation of the applicability of the Meservey-Tedrow
technique to the surface states of **topological** **insulators**

**topological**

**insulators**. Expand abstract.

**topological**surface states is of high interest for possible applications in spintronics. At present, the only technique capable to measure the surface state spin texture is spin and angle resolved photoemission spectroscopy (SARPES). However, values reported by SARPES differed strongly. An established technique to measure the spin polarization of ferromagnetic materials is the so-called Meservey-Tedrow technique, which is based on spin dependent tunneling from a superconducting electrode to a ferromagnet. Here, we theoretically investigate how the Meservey-Tedrow technique can be adapted to

**topological**

**insulators**. We demonstrate that with a specific device geometry it is possible to determine the in-plane component of the spin polarization of

**topological**surface states. More complex device geometries can access the full momentum dependence of the spin polarization. We also show that it is possible to extract the spin-flip scattering rate of surface electrons with the same devices.

10/10 relevant

arXiv

Floquet **topological** **insulators**: from band structure engineering to novel
non-equilibrium quantum phenomena

**topological**phases in many-body Floquet systems is their tendency to absorb energy from the drive and thereby to heat up. Expand abstract.

**topological**phenomena in quantum many-body systems. We discuss how such fields can be used to change the

**topological**properties of the single particle spectrum, and key experimental demonstrations in solid state, cold atomic, and photonic systems. The single particle Floquet band structure provides a stage on which the system's dynamics play out; the crucial question is then how to obtain robust

**topological**behaviour in the many-particle setting. In the regime of mesoscopic transport, we discuss manifestations of

**topological**edge states induced in the Floquet spectrum. Outside the context of mesoscopic transport, the main challenge of inducing stable

**topological**phases in many-body Floquet systems is their tendency to absorb energy from the drive and thereby to heat up. We discuss three routes to overcoming this challenge: long-lived transient dynamics and prethermalization, disorder-induced many-body localization, and engineered couplings to external baths. We discuss the types of phenomena that can be explored in each of these regimes, and their experimental realizations.

8/10 relevant

arXiv

Stability of dynamical quantum phase transitions in quenched **topological**
**insulators**: From multiband to disordered systems

**topological**

**insulators**and superconductors with disorder. Expand abstract.

**topological**properties. Here, we contribute to broadening the systematic understanding of this relation between topology and DQPTs to multi-orbital and disordered systems. Specifically, we provide a detailed ergodicity analysis to derive criteria for DQPTs in all spatial dimensions, and construct basic counter-examples to the occurrence of DQPTs in multi-band

**topological**

**insulator**models. As a numerical case study illustrating our results, we report on microscopic simulations of the quench dynamics in the Harper-Hofstadter model. Furthermore, going gradually from multi-band to disordered systems, we approach random disorder by increasing the (super) unit cell within which random perturbations are switched on adiabatically. This leads to an intriguing order of limits problem which we address by extensive numerical calculations on quenched one-dimensional

**topological**

**insulators**and superconductors with disorder.

10/10 relevant

arXiv