Topological phase diagram of BiTeX-graphene hybrids

\( (d \circ f)\varphi \), Balatonfenyves, 2019

Zoltán Tajkov, PhD Student

ELTE, BFT

\( (d \circ f)\varphi \), Balatonfenyves, 2019

WHY SO TOPOLOGICAL?

  • Dissipationless transistor
  • Quantum Computation
  • Majorana fermions
  • Optoelectronics

\( (d \circ f)\varphi \), Balatonfenyves, 2019

GRAPHENE IS GOOD...

... as a base

\( (d \circ f)\varphi \), Balatonfenyves, 2019

ABOUT GRAPHENE

and its friends

\( (d \circ f)\varphi \), Balatonfenyves, 2019

HOW TO MAKE GRAPHENE TOPOLOGICAL?

\mathcal{H}=\sum_{ij\alpha}t c^\dagger_{i\alpha}c_{j\alpha} \sigma_0

\( (d \circ f)\varphi \), Balatonfenyves, 2019

HOW TO MAKE GRAPHENE TOPOLOGICAL?

\mathcal{H}=\sum_{ij\alpha}t c^\dagger_{i\alpha}c_{j\alpha} \sigma_0+\sum_{ij\alpha\beta}it'c^\dagger_{i\alpha}c_{j\beta}\sigma_z

\( (d \circ f)\varphi \), Balatonfenyves, 2019

HOW TO MAKE GRAPHENE TOPOLOGICAL?

K

 \( E_F \)

t'=0

 \( E_F \)

t'\neq 0

TOPOLOGICAL

turn on SOC

K

\( (d \circ f)\varphi \), Balatonfenyves, 2019

CHANGING THE PROPERTIES OF GRAPHENE

  • Adatoms
  • Strain
  • Curvature
  • Composite

\( (d \circ f)\varphi \), Balatonfenyves, 2019

HOW TO MAKE GRAPHENE TOPOLOGICAL?

Weak inherent SOC...

Buff it!

\( (d \circ f)\varphi \), Balatonfenyves, 2019

HOW TO MAKE GRAPHENE TOPOLOGICAL?

\( (d \circ f)\varphi \), Balatonfenyves, 2019

HOW TO MAKE GRAPHENE TOPOLOGICAL?

K   \( \leftarrow \)    \( \Gamma \)    \( \rightarrow \)   M 

 \( E_F \)

REMAINS METALLIC

\( (d \circ f)\varphi \), Balatonfenyves, 2019

HOW TO MAKE GRAPHENE TOPOLOGICAL?

Pressure!

\( (d \circ f)\varphi \), Balatonfenyves, 2019

HOW TO MAKE GRAPHENE TOPOLOGICAL?

Pressure!

Pressure opens gap!

... but it's trivial...

\( (d \circ f)\varphi \), Balatonfenyves, 2019

HOW TO MAKE GRAPHENE TOPOLOGICAL?

Strain?!

\( (d \circ f)\varphi \), Balatonfenyves, 2019

HOW TO MAKE GRAPHENE TOPOLOGICAL?

\( (d \circ f)\varphi \), Balatonfenyves, 2019

CAN WE UNDERSTAND IT?

\( (d \circ f)\varphi \), Balatonfenyves, 2019

THANK YOU FOR YOUR ATTENTION!

László Oroszlány     János Koltai        Dávid Visontai       Gergő Kukucska

Bálint Fülöp      Szabolcs Csonka        Péter Makk              Sándor Bordács

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