title: Topologically protected Dirac plasmons and their evolution across the quantum phase transition in a (Bi(1-x)In(x))2Se3 topological insulator.
abstract: A 3D Topological Insulator (TI) is an intrinsically stratified electronic material characterized by an insulating bulk and Dirac free electrons at the interface with vacuum or another dielectric. In this paper, we investigate, through terahertz (THz) spectroscopy, the plasmon excitation of Dirac electrons on thin films of (Bi1-xInx)2Se3 TI patterned in the form of a micro-ribbon array, across a Quantum Phase Transition (QPT) from the topological to a trivial insulating phase. The latter is achieved by In doping onto the Bi-site and is characterized by massive electrons at the surface. While the plasmon frequency is nearly independent of In content, the plasmon width undergoes a sudden broadening across the QPT, perfectly mirroring the single particle (free electron) behavior as measured on the same films. This strongly suggests that the topological protection from backscattering characterizing Dirac electrons in the topological phase extends also to their plasmon excitations.
authors: INFN and Dipartimento di Fisica, Università di Roma "La Sapienza", Piazzale A. Moro 2, I-00185 Roma, Italy. stefano.lupi@roma1.infn.it.
authors: Marta
authors: M
authors: Autore
authors: INFN and Dipartimento di Fisica, Università di Roma "La Sapienza", Piazzale A. Moro 2, I-00185 Roma, Italy. stefano.lupi@roma1.infn.it.
authors: Flavio
authors: F
authors: Giorgianni
authors: Istituto Italiano di Tecnologia and Dipartimento di Fisica, Università di Roma "La Sapienza", Piazzale A. Moro 2, I-00185 Roma, Italy.
authors: Fausto
authors: F
authors: D' Apuzzo
authors: CNR - Institute for Photonics and Nanotechnologies, Via Cineto Romano 42, 00156 Rome, Italy.
authors: Alessandra
authors: A
authors: Di Gaspare
authors: Dipartimento di Fisica, Università di Roma "La Sapienza", Piazzale A. Moro 2, I-00185 Roma, Italy.
authors: Irene
authors: I
authors: Lo Vecchio
authors: Department of Physics and Astronomy Rutgers, The State University of New Jersey, 136 Frelinghuysen Road, Piscataway, NJ 08854-8019, USA.
authors: Matthew
authors: M
authors: Brahlek
authors: Department of Physics and Astronomy Rutgers, The State University of New Jersey, 136 Frelinghuysen Road, Piscataway, NJ 08854-8019, USA.
authors: Nikesh
authors: N
authors: Koirala
authors: Department of Physics and Astronomy Rutgers, The State University of New Jersey, 136 Frelinghuysen Road, Piscataway, NJ 08854-8019, USA.
authors: Seongshik
authors: S
authors: Oh
authors: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH Elektronenspeicherring BESSY II, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany.
authors: Urlich
authors: U
authors: Schade
authors: CNR - Institute for Photonics and Nanotechnologies, Via Cineto Romano 42, 00156 Rome, Italy.
authors: Michele
authors: M
authors: Ortolani
authors: INFN and Dipartimento di Fisica, Università di Roma "La Sapienza", Piazzale A. Moro 2, I-00185 Roma, Italy. stefano.lupi@roma1.infn.it.
authors: Stefano
authors: S
authors: Lupi