Photoemission studies of topological insulators
Başlık çevirisi mevcut değil.
- Tez No: 402951
- Danışmanlar: DR. BORIS SINKOVIC
- Tez Türü: Doktora
- Konular: Fizik ve Fizik Mühendisliği, Physics and Physics Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2016
- Dil: İngilizce
- Üniversite: The Unıversıty Of Connectıcut
- Enstitü: Yurtdışı Enstitü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: Belirtilmemiş.
Özet
Özet yok.
Özet (Çeviri)
Topological insulators (TIs) attracted scientist due to its distinct electronic structure. TIs possess metallic surfaces due to strong spin orbit coupling, while the bulk shows the insulating behavior. On the surface of TIs topologically protected surface states obeys the massless Dirac equation, namely electron energy disperses linearly with respect its momentum. In addition, these surface states are protected against to backscattering because of the perpendicular locking of spin and momentum to each other. The work presented in this thesis focused on the growth method of Bi2Se3 topological insulator under the ultra-high vacuum conditions and interaction of the topological surface states of Bi2Se3 with magnetic impurities and superconductors. We presented x-ray photoemission spectroscopy (XPS) and angle resolved photoemission spectroscopy (ARPES) study to demonstrate high crystal quality of Molecular Beam Epitaxy (MBE) grown Bi2Se3 on Al2O3 (0001) substrate. We further supported our study by performing x-ray diffraction (XRD) and low energy electron diffraction (LEED) on Bi2Se3 thin film. In addition, one of the interest on TIs is to introduce magnetic impurities into bulk and on the surface to break time reversal symmetry (TRS), which leads to open an energy gap at the Dirac point of TIs. Such experiment is important for experimental observation of Quantum Anomalous Hall effect. For this reason, XPS and ARPES study on Cr bulk and surface doped Bi2Se3 were presented in order to investigate magnetic impurity doping impact on the electronic and chemical environment of Bi2Se3. ARPES measurements revealed that Cr bulk doping opens an energy gap at the Dirac point without ferromagnetism, while gapless surface states are robust against Cr surface deposition. Another interest on TIs is to obtain proximity induced superconductivity in order to open experimental avenue for possible experimental detection of long sought Majorana fermions. Therefore, we presented ARPES study on Bi2Se3/ Bi2Sr2CaCu2O8+δ (BSCCO) heterostructure in order to search for proximity induced superconductivity. In contrast to expectations, ARPES measurements do not show any sign of the proximity induced superconductivity in the thickness range from 0.5 quintuple layer of Bi2Se3 to 15 quintuple layer of Bi2Se3.
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