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Projects / Programmes source: ARIS

Physics of Majorana fermions in Kitaev magnets

Research activity

Code Science Field Subfield
1.02.01  Natural sciences and mathematics  Physics  Physics of condesed matter 

Code Science Field
1.03  Natural Sciences  Physical sciences 
Keywords
quantum magnetism, quantum spin liquids, Kitaev magnet, anyons, Majorana fermions, topological matter, nuclear magnetic resonance
Evaluation (rules)
source: COBISS
Points
1,840.96
A''
509.21
A'
881.62
A1/2
1,451.89
CI10
3,272
CImax
114
h10
28
A1
6.8
A3
0
Data for the last 5 years (citations for the last 10 years) on March 3, 2024; A3 for period 2018-2022
Data for ARIS tenders ( 04.04.2019 – Programme tender, archive )
Database Linked records Citations Pure citations Average pure citations
WoS  260  5,171  4,212  16.2 
Scopus  263  5,475  4,484  17.05 
Researchers (6)
no. Code Name and surname Research area Role Period No. of publicationsNo. of publications
1.  53450  Tina Arh  Physics  Junior researcher  2020 - 2024  35 
2.  39140  PhD Nejc Janša  Physics  Junior researcher  2020 - 2021  12 
3.  20209  PhD Martin Klanjšek  Physics  Head  2020 - 2024  193 
4.  32911  PhD Georgios Kordogiannis  Physics  Researcher  2021 - 2024  182 
5.  26465  PhD Matej Pregelj  Physics  Researcher  2020 - 2024  130 
6.  21558  PhD Andrej Zorko  Physics  Researcher  2020 - 2024  290 
Organisations (1)
no. Code Research organisation City Registration number No. of publicationsNo. of publications
1.  0106  Jožef Stefan Institute  Ljubljana  5051606000  90,038 
Abstract
This project aims to be at the heart of lively and fascinating field of research initiated by Alexei Kitaev in 2006 with his seminal paper "Anyons in an exactly solved model and beyond". Kitaev showed that the exact ground state of the spin-1/2 model on a honeycomb lattice with bond-dependent Ising interactions is a topological quantum spin liquid, whose elementary excitations are two distinct types of fractional quasiparticles, i.e., Majorana fermions and gauge Z2 fluxes. They turn out to be anyons, meaning that they are neither fermions nor bosons. Their main virtue is that, in contrast to fermions or bosons, the exchange operations between anyons are topologically protected. This makes them stable against various types of disorder including thermal effects. Kitaev suggested that such a honeycomb magnet thus offers a unique potential platform for intrinsically fault-tolerant quantum computer and even developed the corresponding computing protocols. In the last five years, a-RuCl3 has been recognized as the most promising realization of the Kitaev honeycomb model. In the last two years, observations consistent with the existence of anyons in a-RuCl3 accumulated, perhaps the most straightforward two being reported in 2018 by the Japanese group in Nature and by the group led by me in Nature Physics. Now that the existence of anyons in a-RuCl3 is established, their highly unusual properties should be inspected, in order to be once able to manipulate them for the purpose of quantum computing. This opens three immediate problems related to the properties of anyons in Kitaev materials. (1) How do the properties of anyons and, in particular, Majorana fermions change across the phase diagram spanned by the external parameters, such as temperature, magnetic field, hydrostatic pressure, electron doping? (2) What kind of novel physics can one expect in the collective behavior of Majorana fermions? A theory predicts an intriguing formation of a thermal metal of Majorana fermions. The experimental evidence of such a bulk conductor of spin density instead of electricity, which would start to conduct only when thermally excited, is still missing. (3) Could novel Kitaev materials, which would overcome the drawback of a-RuCl3 that it orders magnetically at low temperatures and low magnetic fields, offer cleaner Kitaev physics and thus more perfect realization of anyons, where BaCo2As2O8 is the most recent example? We will address these three problems using nuclear magnetic resonance (NMR) as the main experimental technique. NMR is a very powerful technique for measuring the static and dynamic spin responses of quantum magnets, complementary to neutron scattering techniques. When necessary, we will complement NMR with magnetic property measurements, muon spin rotation (uSR) and electron spin resonance (ESR) characterization. Using these techniques, we will study Kitaev materials a-RuCl3 and BaCo2As2O8. We will compare the experimental results to numerous recently obtained and thus not yet tested theoretical predictions, such as the existence of the exotic thermal metal phase of Majorana fermions. As Kitaev materials currently represent a very active and fascinating field of research on the crossroads of topological properties of matter (2016 Nobel prize for physics) and quantum computing (Quantum Flagship funded by European Commission from October 2018 as the third such large-scale EU initiative), the proposed project is highly relevant and its results are certainly anticipated.
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