Search query: From Andreev to Majorana Natural review

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abstract: Inhomogeneous superconductors can host electronic excitations, known as Andreev bound states (ABSs) below the superconducting energy gap. With the advent of topological superconductivity, a new kind of zero energy ABS with exotic qualities, known as a Majorana bound state (MBS) has been discovered. A special property of MBS wavefunctions is their non locality, which, together with non Abelian braiding, is the key to their promise in topological quantum computation. We focus on hybrid superconductor semiconductor nanowires as a flexible and promising experimental platform to realize one dimensional topological superconductivity and MBSs. We review the main properties of ABSs and MBSs, state of the art techniques for their detection and theoretical progress beyond minimal models, including different types of robust zero modes that may emerge without a band topological transition. Topological Majorana bound states have potential for encoding, manipulating and protecting quantum information in condensed matter systems. This Review discusses emergence and characterization of Majorana bound states in realistic devices based on hybrid semiconducting nanowires and their connection to more conventional Andreev bound states. Non uniform superconductors and hybrid normal metal superconducting systems can develop discrete bound states inside the superconducting gap, known as Andreev bound states (ABSs) through Andreev reflection processes. Andreev bound states are a superposition of electrons and holes, and can also develop a non trivial spin structure if the system exhibits spin orbit coupling and low densities, as is the case in proximitized semiconducting nanowires. Precise experimental characterization of ABSs in proximitized nanowires is now possible through a range of spectroscopic techniques, including tunnelling transport, quantum dot spectroscopy and microwave cavity spectroscopy. The interplay of spin orbit coupling, Zeeman fields and low densities in proximitized semiconducting nanowires can induce a quantum phase transition into a topological superconducting phase, whereupon ABSs transform into zero energy, topologically protected Majorana bound states (MBSs) with exotic properties, promising for quantum computation purposes. The experimental search for MBSs in proximitized nanowires has encountered a rich and complex phenomenology that has required standard theoretical models to be extended substantially, revealing in the process a host of mechanisms for the emergence of zero energy bound states beyond the original band topological framework. These states are known in the field as quasi MBSs, partially separated MBSs or non topological MBSs.
author_names: Elsa Prada

Pablo San-Jose

Michiel W A de Moor

Attila Geresdi

Eduardo J H Lee

Jelena Klinovaja

Daniel Loss

Jesper Nygard

Ramon Aguado

L P Kouwenhoven
title: From Andreev to Majorana bound states in hybrid superconductor semiconductor nanowires
year: 2019

abstract: Zero energy Andreev levels in hybrid semiconductor superconductor nanowires mimic all expected Majorana phenomenology, including $2{e}{2}/h$$2e2/h conductance quantisation, even where band topology predicts trivial phases. This surprising fact has been used to challenge the interpretation of various transport experiments in terms of Majorana zero modes. Here we show that the Andreev versus Majorana controversy is clarified when framed in the language of non Hermitian topology, the natural description for quantum systems open to the environment. This change of paradigm allows one to understand topological transitions and the emergence of zero modes in more general systems than can be described by band topology. This is achieved by studying exceptional point bifurcations in the complex spectrum of the system's non Hermitian Hamiltonian. Within this broader topological classification, Majoranas from both conventional band topology and a large subset of Andreev levels at zero energy are in fact topologically equivalent, which explains why they cannot be distinguished.The existence of Majorana zero modes have been potentially confirmed in superconductor semiconductor nanowires but recent studies suggest the data can also be interpreted using Andreev bound states, throwing into doubt the conclusions regarding Majorana modes. To resolve this controversy the authors use non Hermitian topology to determine the boundaries between the Majorana and Andreev states.
author_names: Julio Avila

Fernando Penaranda

Elsa Prada

Pablo San-Jose

Ramon Aguado
title: Non hermitian topology as a unifying framework for the Andreev versus Majorana states controversy
venue: Communications Physics
year: 2019

abstract: The aim of the present work is to gather the data already acquired about the use of Origanum majorana (manjerona) botanical characteristics, main constituents and scientific studies about the species as a phytotherapeutic agent in dentistry, focusing on potential use as anxiolytic. A literature review was conducted from 2009 to 2019 on the Academic Google and Scientific Electronic Library Online search platforms. The main constituents identified in O. majorana essential oil were terpinen 4 ol, g terpinene and a terpinene. Another important compound of this species would be cis terpineol, which would have anesthetic activity and the potential to modulate GABA A capacity. Studies conducted with O. majorana essential oils promoted muscle relaxation in the gastropod Pomacea canaliculata at concentrations above 100mL L 1, as well as sedation in the fish species Rhamdia quelen at a concentration of 100 mL L 1, and anesthesia at concentrations of 200, 300, 400 and 500 mL L 1 Marjoram is also attributed to antimicrobial, antioxidant, anesthetic, relaxing and cytotoxic effects. Origanum majorana is a species widely used in the treatment of Central Nervous System disorders due to its antiepileptic and sedative effects. Recent research has shown that the antimicrobial effect is also present, but further studies focusing only on isolated microbial strains are needed. Although their results are proving to be effective, it must be emphasized that natural products can also have adverse effects.
author_names: Gabrielli Bezerra Sales

Janaina Barbosa de Alencar

Rafaela Oliveira Santos

Servulo da Costa Rodrigues Neto

Aleson Sousa

Abrahao Alves de Oliveira Filho
title: Origanum majorana as ansiolitic agent in dentistry: a literary review
year: 2020

abstract: Focusing specifically on the recently retracted Nature 2018 Zhang et al. work [Zhang et al. Nature (2021) and the related recently available correctly analyzed data from this Delft experiment [Zhang et al. arXiv:2101.11456 (2021) we discuss the general problem of confirmation bias in experiments verifying various theoretical topological quantization predictions. We show that the Delft Majorana experiment is most likely dominated by disorder, which produces trivial (but quite sharp and large) zero bias Andreev tunneling peaks with large conductance 2e/h in the theory, closely mimicking the data. Thus, although the corrected Delft data are by far the best tunnel spectroscopy results available in the literature, manifesting large and sharp zero bias peaks rising above the background with an impressive hard superconducting gap, our theory shows that the most natural explanation for these zero bias peaks is that they are disorder induced and not topological Majorana modes. It is possible to misinterpret such disorder induced zero bias trivial peaks as the apparent Majorana quantization, as was originally done in 2018 arising from confirmation bias. One characteristic of the disorder induced trivial peaks is that they manifest little stability as a function of Zeeman field, chemical potential, and tunnel barrier, distinguishing their trivial behavior from the expected topological robustness of non Abelian Majorana zero modes. We also analyze a more recent nanowire experiment [Yu et al. Nature Physics (2021) which is known to have a huge amount of disorder, showing that such highly disordered nanowires may produce very small above background trivial peaks with conductance values 2e/h in a dirty system manifesting very soft superconducting gap with substantial in gap conduction, as were already reported by several groups almost 10 years ago. Removing disorder and producing cleaner samples through materials quality improvement and better fabrication is the only way for future progress in this field.
author_names: Sankar Das Sarma

Haining Pan
title: Disorder induced zero bias peaks in Majorana nanowires
year: 2021

abstract: The search for new states that exhibit topological order is currently a very active and exciting area of research. Like a topological insulator, superconducting order can also exhibit topological order, which is different from that of a conventional superconductor. This superconductor is so called " topological superconductor" which has a full pairing gap in the bulk and gapless surface state. Majorana Fermions obey non Abelian fractional statistics, and have been proposed to construct topological qubits, so there is a great prospect of scientific research and application in topological quantum computing. It is very interesting that Majorana Fermions are predicted to exist in topological superconductors. However, natural topological superconductor is very rare. Inspired by the realization of topological insulators, theoretical physicists have proposed that via the fabrication of the s wave superconductor/topological insulator heterostructure, Majorana Fermions may exist in the superconducting topological insulator induced by proximate effect. Due to various kinds of topological insulators and conventional s wave superconductors, heterostructures constructed by this method can greatly increase the variety of artificial topological superconductors. In this paper we review the experimental progress in the heterostructure composed of the Bi2Te3 type topological insulator and the conventional s wave superconductor NbSe2. Using molecular beam epitaxy, atomically flat topological insulator film can be fabricated at the top of superconductor substrate. The spatial distribution of Majorana Fermions on the surface of topological insulator can be directly observed by in situ scanning tunneling microscopy/spectroscopy. In the center of a magnetic vortex, Majorana Fermions will appear as the Majorana zero mode, a zero energy peak inside the superconducting gap. Although the energy gap between low energy quasiparticle excitation and the Majorana zero mode is very small, the evidences such as zero bias conductance anomaly, Y shape splitting of zero bias conductance, spin selective Andreev reflection are self consistent and reveal that the Majorana zero mode exists in the center of a magnetic vortex. These experiments have led to a new insight into superconductivity. It may open a door to probing the novel physics of Majorana fermions.
author_names: Li Yaoyi

Jia Jin-Feng
title: Search for Majorana zero mode in the magnetic vortex of artificial topological superconductor
year: 2019

abstract: The epidemic associated with the new Sars CoV 2 coronavirus has affected almost all countries of the world and no reliable treatment for this infection exists yet Many laboratories in the world are currently conducting intensive experimental and theoretical/in silico studies to find effective drugs specific for this disease (COVID 19) but unfortunately, it may take a long time before new drugs appear in the clinical practice One of the currently widely accepted approaches for finding active compounds is based on the possibility of using existing drugs approved by government medical organizations (as the FDA) Their choice is based on screening, based on the use of computer models that evaluate the specific binding (energy minimization) of such drugs to target molecules that are important for the life cycle Thus, a few well known antiviral drugs against HIV, hepatitis C and others selected on this basis exerted an antiviral effect in vitro, but their real effectiveness was far from expected It should be emphasized that the severe clinical manifestation of the disease is an acute respiratory distress syndrome, mediated by oxidative stress and an aggressive immune attack on its own cells In this regard, the use of compounds with high antioxidant activity could have advantages both prophylactically and medically There is a huge range of natural compounds, including official and traditional medicine, which represent valuable unlimited potential for COVID 19 therapy, the advantage of such compounds in their low toxicity In this review, we tried to focus on the clinical and pharmacological properties of natural substances, mainly flavonoids, which can become promising drugs for the treatment and prevention of COVID 19 The review includes information on possible virus targets and antiviral drugs Much attention is paid to the question of inhibition of viral activity Based on published data, including structural features of various compounds, a prediction is made about the prospects of using these compounds as inhibitors of viral activity, as well as anti inflammatory drugs for the treatment of COVID 19 An important step in the analysis of compounds was the study of the possibility of their interaction with cellular targets of the virus, as well as the ability to bind to the proteins of the Sars CoV 2 virus itself Epidemiia, sviazannaia s novym koronavirusom Sars CoV 2, porazila prakticheski vse strany zemnogo shara, i nadezhnykh lechebnykh sredstv ot etoi infektsii poka ne sushchestvuet Mnogie laboratorii v mire v nastoiashchee vremia vedut intensivnye eksperimental'nye i teoreticheskie issledovaniia s tsel'iu poiska effektivnykh preparatov, spetsifichnykh dlia etogo zabolevaniia (COVID 19) no, k sozhaleniiu, mozhet potrebovat'sia mnogo vremeni, prezhde chem novye lekarstva poiaviatsia v klinicheskoi praktike Odin iz samykh populiarnykh podkhodov osnovan na vozmozhnosti ispol'zovaniia dlia lecheniia sushchestvuiushchikh preparatov, odobrennykh pravitel'stvennymi meditsinskimi organizatsiiami Ikh vybor osnovan na skrininge, v osnove kotorogo lezhit ispol'zovanie komp'iuternykh modelei, otsenivaiushchikh spetsificheskoe sviazyvanie (minimizatsiia energii sviazyvaniia) takikh preparatov s molekulami misheniami, vazhnykh dlia zhiznennogo tsikla Tak, riad izvestnykh antivirusnykh preparatov protiv VICh, gepatita S, vybrannykh podobnym obrazom, okazyvali protivovirusnyi effekt in vitro, no ikh klinicheskaia effektivnost' byla nevysokoi Sleduet podcherknut' chto tiazhelaia forma klinicheskogo proiavleniia zabolevaniia predstavliaet soboi ostryi respiratornyi distress sindrom, oposredovannyi okislitel'nym stressom i agressivnoi immunnoi atakoi na sobstvennye kletki V etoi sviazi primenenie soedinenii s vysokoi antioksidantnoi aktivnost'iu mozhet imet' preimushchestva kak v profilakticheskom, tak i v lechebnom plane Sushchestvuet ogromnyi spektr prirodnykh soedinenii, vkliuchaia preparaty ofitsial'noi i traditsionnoi meditsiny, kotorye predstavliaiut neogranichennyi potentsial, v tom chisle dlia terapii virusnykh zabolevanii Osnovnym preimushchestvom podobnykh soedinenii iavliaetsia ikh nizkaia toksichnost' V dannom obzore my postaralis' sdelat' aktsent na klinicheskie i farmakologicheskie svoistva prirodnykh veshchestv, preimushchestvenno flavonoidov, kotorye mogut stat' perspektivnymi preparatami dlia lecheniia i profilaktiki COVID 19 V obzor vkliuchena informatsiia o vozmozhnykh misheniakh virusa i protivovirusnykh preparatakh Bol'shoe vnimanie udeleno voprosu ingibirovaniia virusnoi aktivnosti Na osnove literaturnykh dannykh, v tom chisle o strukturnykh osobennostiakh razlichnykh soedinenii, sdelan prognoz o perspektivnosti ispol'zovaniia dannykh soedinenii v kachestve ingibitorov virusnoi aktivnosti, a takzhe v kachestve protivovospalitel'nykh sredstv dlia terapii COVID 19 Vazhnym etapom pri analize soedinenii bylo izuchenie vozmozhnosti ikh vzaimodeistviia s kletochnymi misheniami virusa, a takzhe sposobnosti sviazyvaniia s belkami samogo virusa Sars CoV 2
author_names: Sergey M Andreev

Nadezhda Shershakova

Ksenia V Kozhikhova

Artyom A Shatilov

Anastasiia V Timofeeva

Evgeny A Turetskiy

Dmitry A Kudlay

Musa R Khaitov
title: Promising compounds from natural sources against COVID 19
year: 2020

abstract: This review paper presents a framework to evaluate the artificial intelligence (AI) readiness for the healthcare sector in developing countries: a combination of adequate technical or technological expertise, financial sustainability, and socio political commitment embedded in a healthy psycho cultural context could bring about the smooth transitioning toward an AI powered healthcare sector. Taking the Vietnamese healthcare sector as a case study, this paper attempts to clarify the negative and positive influencers. With only about 1500 publications about AI from 1998 to 2017 according to the latest Elsevier AI report, Vietnamese physicians are still capable of applying the state of the art AI techniques in their research. However, a deeper look at the funding sources suggests a lack of socio political commitment, hence the financial sustainability, to advance the field. The AI readiness in Vietnam's healthcare also suffers from the unprepared information infrastructure using text mining for the official annual reports from 2012 to 2016 of the Ministry of Health, the paper found that the frequency of the word "database" actually decreases from 2012 to 2016, and the word has a high probability to accompany words such as "lacking" "standardizing" "inefficient" and "inaccurate." Finally, manifestations of psycho cultural elements such as the public's mistaken views on AI or the non transparent, inflexible and redundant of Vietnamese organizational structures can impede the transition to an AI powered healthcare sector.
author_names: Quan-Hoang Vuong

Thu-Trang Vuong

Viet-Phuong La

Kien-Cuong P Nghiem

Hai-Ha Giang

Thu-Vu Giang

Carl A Latkin

Roger C M Ho
title: Artificial Intelligence vs. Natural Stupidity: Evaluating AI Readiness for the Vietnamese Medical Information System
venue: Journal of clinical medicine
year: 2019

abstract: In these notes, we review the main results of our approach to fermion masses. The marge mass ratios between fermions, confronted with a unique breaking mechanism leading to vector bosons masses, led us to consider the possibility that they result from the overlap of fermion wave functions. Such overlaps vary indeed very strongly if the observed fermion families in 4 dimensions originate in a single family in 6 dimensions, through localized wave functions. This framework leads in a natural way to large mass ratios and small mixing angles between quarks. What came as a surprise is that if we impose that neutrinos behave as 2 component "Majorana" particles in 4D, a completely different situation is obtained for them. Instead of diagonal mass matrices, anti diagonal ones emerge and lead to a generic prediction of combined inverted hierarchy, large mixing angles in the leptonicsector, and a suppression of neutrinoless double beta decay placing it at the lower limit of the inverted hierarchy branch, a challenging situation for on going and planned experiments. Our approach predicted the size of the th13 mixing angle before its actual measurement. Possible signals at colliders are only briefly evoked.
author_names: Jean Marie Frere

Maxim Libanov

Simon Mollet

S V Troitsky
title: Fermion masses from six dimensions and implications for Majorana neutrinos
year: 2014

abstract: We suggest a way to overcome the obstacles that disorder and high density of states pose to the creation of unpaired Majorana fermions in onedimensional systems. This is achieved by splitting the system into a chain of quantum dots, which are then tuned to the conditions under which the chain can be viewed as an effective Kitaev model, so that it is in a robust topological phase with well localized Majorana states in the outermost dots. The tuning algorithm that we develop involves controlling the gate voltages and the superconducting phases. Resonant Andreev spectroscopy allows us to make the tuning adaptive, so that each pair of dots may be tuned independently of the other. The calculated quantized zero bias conductance serves then as a natural proof of the topological nature of the tuned phase. 4 Author to whom any correspondence should be addressed. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. New Journal of Physics 15 (2013) 04502
author_names: Hoi-Yin Hui

J P Dahlhaus

Bjorn Zocher

Mats Horsdal

Bernd Rosenow

Patrik Recher
title: Adaptive tuning of Majorana fermions in a quantum dot chain
year: 2013

abstract: We review recent progress in the exploration of topological quantum states of matter in iron based superconductors. In particular, we focus on the non trivial topology existing in the band structures and superconducting states of iron's 3d orbitals. The basic concepts, models, materials and experimental results are reviewed. The natural integration between topology and high temperature superconductivity in iron based superconductors provides great opportunities to study topological superconductivity and Majorana modes at high temperature.
author_names: Ningning Hao

Jiangping Hu
title: Topological quantum states of matter in iron based superconductors: from concept to material realization
year: 2019