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Realization of a vertical topological p-n junction in epitaxial Sb2Te3/Bi2Te3 heterostructures.

Eschbach M, Młyńczak E, Kellner J, Kampmeier J, Lanius M, Neumann E, Weyrich C, Gehlmann M, Gospodarič P, Döring S, Mussler G, Demarina N, Luysberg M, Bihlmayer G, Schäpers T, Plucinski L, Blügel S, Morgenstern M, Schneider CM, Grützmacher D - Nat Commun (2015)

Bottom Line: Three-dimensional (3D) topological insulators are a new state of quantum matter, which exhibits both a bulk band structure with an insulating energy gap as well as metallic spin-polarized Dirac fermion states when interfaced with a topologically trivial material.Here we show a direct experimental proof by angle-resolved photoemission of the realization of a vertical topological p-n junction made of a heterostructure of two different binary 3D TI materials Bi2Te3 and Sb2Te3 epitaxially grown on Si(111).We demonstrate that the chemical potential is tunable by about 200 meV when decreasing the upper Sb2Te3 layer thickness from 25 to 6 quintuple layers without applying any external bias.

View Article: PubMed Central - PubMed

Affiliation: Forschungszentrum Jülich GmbH, Peter Grünberg Institute (PGI-6) and JARA-FIT, 52425 Jülich, Germany.

ABSTRACT
Three-dimensional (3D) topological insulators are a new state of quantum matter, which exhibits both a bulk band structure with an insulating energy gap as well as metallic spin-polarized Dirac fermion states when interfaced with a topologically trivial material. There have been various attempts to tune the Dirac point to a desired energetic position for exploring its unusual quantum properties. Here we show a direct experimental proof by angle-resolved photoemission of the realization of a vertical topological p-n junction made of a heterostructure of two different binary 3D TI materials Bi2Te3 and Sb2Te3 epitaxially grown on Si(111). We demonstrate that the chemical potential is tunable by about 200 meV when decreasing the upper Sb2Te3 layer thickness from 25 to 6 quintuple layers without applying any external bias. These results make it realistic to observe the topological exciton condensate and pave the way for exploring other exotic quantum phenomena in the near future.

No MeSH data available.


Field-dependent transport measurements.Hall resistance Rxy of four different samples with varying top Sb2Te3 layer thickness investigated at fixed gate voltages and low temperature. For thinner top layer thickness of 3 QL (black curve) and 6 QL (green curve), the heterostructure is in an n-type (electron) transport regime, whereas for thicker films of 17 QL (red curve) and 28 QL (blue curve) p-type (hole) transport is dominant.
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f2: Field-dependent transport measurements.Hall resistance Rxy of four different samples with varying top Sb2Te3 layer thickness investigated at fixed gate voltages and low temperature. For thinner top layer thickness of 3 QL (black curve) and 6 QL (green curve), the heterostructure is in an n-type (electron) transport regime, whereas for thicker films of 17 QL (red curve) and 28 QL (blue curve) p-type (hole) transport is dominant.

Mentions: High-quality MBE-grown Bi2Te3 films are known to exhibit mostly n-type charge carriers due to Te vacancies that introduce donors. Besides vacancies, also ionized BiTe antisite defects generate the n-type doping1719. On the contrary, in Sb2Te3 the major defects are SbTe antisite defects, which impose p-type charge carriers. For this reason, Sb2Te3/Bi2Te3 heterostructures are expected to exhibit a separation of opposite carrier character making them a natural p–n junction system. To prove the existence of different regimes of charge carrier types, we performed magnetic field-dependent transport measurements at 1.4 K in standard Hall-bar geometry with sample widths between 20 and 40 μm and lengths between 150 and 300 μm.. The resulting Hall resistances are shown in Fig. 2.


Realization of a vertical topological p-n junction in epitaxial Sb2Te3/Bi2Te3 heterostructures.

Eschbach M, Młyńczak E, Kellner J, Kampmeier J, Lanius M, Neumann E, Weyrich C, Gehlmann M, Gospodarič P, Döring S, Mussler G, Demarina N, Luysberg M, Bihlmayer G, Schäpers T, Plucinski L, Blügel S, Morgenstern M, Schneider CM, Grützmacher D - Nat Commun (2015)

Field-dependent transport measurements.Hall resistance Rxy of four different samples with varying top Sb2Te3 layer thickness investigated at fixed gate voltages and low temperature. For thinner top layer thickness of 3 QL (black curve) and 6 QL (green curve), the heterostructure is in an n-type (electron) transport regime, whereas for thicker films of 17 QL (red curve) and 28 QL (blue curve) p-type (hole) transport is dominant.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4660041&req=5

f2: Field-dependent transport measurements.Hall resistance Rxy of four different samples with varying top Sb2Te3 layer thickness investigated at fixed gate voltages and low temperature. For thinner top layer thickness of 3 QL (black curve) and 6 QL (green curve), the heterostructure is in an n-type (electron) transport regime, whereas for thicker films of 17 QL (red curve) and 28 QL (blue curve) p-type (hole) transport is dominant.
Mentions: High-quality MBE-grown Bi2Te3 films are known to exhibit mostly n-type charge carriers due to Te vacancies that introduce donors. Besides vacancies, also ionized BiTe antisite defects generate the n-type doping1719. On the contrary, in Sb2Te3 the major defects are SbTe antisite defects, which impose p-type charge carriers. For this reason, Sb2Te3/Bi2Te3 heterostructures are expected to exhibit a separation of opposite carrier character making them a natural p–n junction system. To prove the existence of different regimes of charge carrier types, we performed magnetic field-dependent transport measurements at 1.4 K in standard Hall-bar geometry with sample widths between 20 and 40 μm and lengths between 150 and 300 μm.. The resulting Hall resistances are shown in Fig. 2.

Bottom Line: Three-dimensional (3D) topological insulators are a new state of quantum matter, which exhibits both a bulk band structure with an insulating energy gap as well as metallic spin-polarized Dirac fermion states when interfaced with a topologically trivial material.Here we show a direct experimental proof by angle-resolved photoemission of the realization of a vertical topological p-n junction made of a heterostructure of two different binary 3D TI materials Bi2Te3 and Sb2Te3 epitaxially grown on Si(111).We demonstrate that the chemical potential is tunable by about 200 meV when decreasing the upper Sb2Te3 layer thickness from 25 to 6 quintuple layers without applying any external bias.

View Article: PubMed Central - PubMed

Affiliation: Forschungszentrum Jülich GmbH, Peter Grünberg Institute (PGI-6) and JARA-FIT, 52425 Jülich, Germany.

ABSTRACT
Three-dimensional (3D) topological insulators are a new state of quantum matter, which exhibits both a bulk band structure with an insulating energy gap as well as metallic spin-polarized Dirac fermion states when interfaced with a topologically trivial material. There have been various attempts to tune the Dirac point to a desired energetic position for exploring its unusual quantum properties. Here we show a direct experimental proof by angle-resolved photoemission of the realization of a vertical topological p-n junction made of a heterostructure of two different binary 3D TI materials Bi2Te3 and Sb2Te3 epitaxially grown on Si(111). We demonstrate that the chemical potential is tunable by about 200 meV when decreasing the upper Sb2Te3 layer thickness from 25 to 6 quintuple layers without applying any external bias. These results make it realistic to observe the topological exciton condensate and pave the way for exploring other exotic quantum phenomena in the near future.

No MeSH data available.