Projekteja vuodessa
Abstrakti
The typeII Weyl and typeII Dirac points emerge in semimetals and also in relativistic systems. In particular, the typeII Weyl fermions may emerge behind the event horizon of black holes. In this case the horizon with Painlevé–Gullstrand metric serves as the surface of the Lifshitz transition. This relativistic analogy allows us to simulate the black hole horizon and Hawking radiation using the fermionic superfluid with supercritical velocity, and the Dirac and Weyl semimetals with the interface separating the typeI and typeII states. The difference between such type of the artificial event horizon and that which arises in acoustic metric is discussed. At the Lifshitz transition between typeI and typeII fermions the Dirac lines may also emerge, which are supported by the combined action of topology and symmetry. The typeII Weyl and Dirac points also emerge as the intermediate states of the topological Lifshitz transitions. Different configurations of the Fermi surfaces, involved in such Lifshitz transition, are discussed. In one case the typeII Weyl point connects the Fermi pockets and the Lifshitz transition corresponds to the transfer of the Berry flux between the Fermi pockets. In the other case the typeII Weyl point connects the outer and inner Fermi surfaces. At the Lifshitz transition the Weyl point is released from both Fermi surfaces. They loose their Berry flux, which guarantees the global stability, and without the topological support the inner surface disappears after shrinking to a point at the second Lifshitz transition. These examples reveal the complexity and universality of topological Lifshitz transitions, which originate from the ubiquitous interplay of a variety of topological characters of the momentumspace manifolds. For the interacting electrons, the Lifshitz transitions may lead to the formation of the dispersionless (flat) band with zero energy and singular density of states, which opens the route to roomtemperature superconductivity. Originally, the idea of the enhancement of T_{c} due to flat band has been put forward by the nuclear physics community, and this also demonstrates the close connections between different areas of physics.
Alkuperäiskieli  Englanti 

Sivut  276299 
Sivumäärä  24 
Julkaisu  Journal of Low Temperature Physics 
Vuosikerta  189 
Numero  56 
DOI  pysyväislinkit  
Tila  Julkaistu  1 jouluk. 2017 
OKMjulkaisutyyppi  A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä 
Sormenjälki
Sukella tutkimusaiheisiin 'Lifshitz Transitions, TypeII Dirac and Weyl Fermions, Event Horizon and All That'. Ne muodostavat yhdessä ainutlaatuisen sormenjäljen.Projektit
 2 Päättynyt

TOPVAC: From Topological Matter to Relativistic Quantum Vacuum
Volovik, G., Nissinen, J., Eltsov, V., Rysti, J., Rantanen, R., Mäkinen, J., Zhang, K., Volard, M., Kamppinen, T. & Ikäheimo, A.
01/10/2016 → 30/09/2022
Projekti: EU: ERC grants

Matalien lämpötilojen kvanttiilmiöiden ja komponenttien huippuyksikkö
Eltsov, V., Hietala, N., Rysti, J., Mäkinen, J. & Volovik, G.
01/01/2015 → 31/12/2017
Projekti: Academy of Finland: Other research funding