Interplay of Superconducting Gap and Spin-Orbit Coupling in Rhombohedral Graphite Proximitized by NbSe2

Zoltán Tajkov

IEEE NAP, Sept 14, 2023

Centre of Low Temperature Physics, Institute of Experimental Physics, Slovak Academy of Sciences

This work was supported by the Slovak Academy of Sciences project IMPULZ IM-2021-42

outline of the talk

ABC graphite

The unique properties of ABC-stacked rhombohedral graphite. Flat band emerged from SSH chain like topology, strongly correlated states around the Fermi energy,

nbse2

Single layer superconductor niobium diselenide is an Ising superconductor, has quantum metallic state, and  hosts strong enhancement of charge density wave order.

Heterostructure

Combining 2D materials in heterostructures unlocks potent synergies, enhancing their properties and catalyzing scientific and technological breakthroughs.

IEEE NAP, Sept 14, 2023

ABC graphite

E(\mathbf{q}) \propto |\mathbf{q}|^N

SSH chain

Imre Hagymási et al., Sci. Adv.8,eabo6879(2022)

IEEE NAP, Sept 14, 2023

outline of the talk

ABC graphite

The unique properties of ABC-stacked rhombohedral graphite. Flat band emerged from SSH chain like topology, strongly correlated states around the Fermi energy and

nbse2

Single layer superconductor niobium diselenide is an Ising superconductor, has quantum metallic state, and  hosts strong enhancement of charge density wave order.

Heterostructure

Combining 2D materials in heterostructures unlocks potent synergies, enhancing their properties and catalyzing scientific and technological breakthroughs.

IEEE NAP, Sept 14, 2023

nbse2

F. Soto et al. / Physica C 460–462 (2007) 789–790

M. R. Sahu et al. Phys. Rev. B 94, 235451 2016

\( T_c \approx 7 K \)

\( 2\Delta \approx 2.7 \, \mathrm{meV} \)

Xi, X., et al. Nature Phys 12, 139–143 (2016).

Ising superconductor

IEEE NAP, Sept 14, 2023

outline of the talk

ABC graphite

The unique properties of ABC-stacked rhombohedral graphite. Flat band emerged from SSH chain like topology, strongly correlated states around the Fermi energy and

nbse2

Single layer superconductor niobium diselenide is an Ising superconductor, has quantum metallic state, and  hosts strong enhancement of charge density wave order.

Heterostructure

Combining 2D materials in heterostructures unlocks potent synergies, enhancing their properties and catalyzing scientific and technological breakthroughs.

IEEE NAP, Sept 14, 2023

Heterostructure

26 C

7 Se

7 Nb

7 Se

Rotation angle 13.89°

Missfit is 3%

The unit cell contains

  • 14 Se
  • 7 Nb
  • 26 \(\times\) (number of graphene layers) C

DFT

Fully relaxed geometry

Single points SOC calculation

Geometry

BZ of a regular graphene unit cell

BZ of the investigated unit cell

IEEE NAP, Sept 14, 2023

Heterostructure

1 layer of C

2 layers of C

3 layers of C

4 layers of C

5 layers of C

6 layers of C

Band structures

Heterostructure

1 layer of C

2 layers of C

3 layers of C

4 layers of C

5 layers of C

6 layers of C

Band structures

Heterostructure

1 layer of C

2 layers of C

3 layers of C

4 layers of C

5 layers of C

6 layers of C

Band structures

Heterostructure

1 layer of C

2 layers of C

3 layers of C

4 layers of C

5 layers of C

6 layers of C

Band structures

Heterostructure

1 layer of C

2 layers of C

3 layers of C

4 layers of C

5 layers of C

6 layers of C

Band structures

Heterostructure

1 layer of C

2 layers of C

3 layers of C

4 layers of C

5 layers of C

6 layers of C

Band structures

Heterostructure

1 layer of C

2 layers of C

3 layers of C

4 layers of C

5 layers of C

6 layers of C

Band structures

Heterostructure

Tight binding

FIT

\( \gamma_0 \) is set

Graphite parameters obtained by SIESTA calculations without the NbSe\(_2\) layers

We solely contemplated the contributions of \( p_z\) orbitals.

Heterostructure

Tight binding

FIX

fixed \( \gamma_0 \) 

FIT

\( \gamma_0 \) is fix, fit \( \gamma_{1,2,3} \) 

Graphite parameters obtained by SIESTA calculations without the NbSe\(_2\) layers

We solely contemplated the contributions of \( p_z\) orbitals.

IEEE NAP, Sept 14, 2023

Heterostructure

Tight binding

\( \gamma_i \)  fixed

 NbSe\(_2\) influences the on-site terms

Heterostructure

Tight binding

\( \gamma_i \)  fixed

 NbSe\(_2\) influences the on-site terms

Heterostructure

Tight binding

\( \gamma_i \)  fixed

 NbSe\(_2\) influences the on-site terms

Heterostructure

Tight binding

\( \gamma_i \)  fixed

 NbSe\(_2\) influences the on-site terms

\( e^{\left( -\alpha N \right)} \)

$$\alpha=1.001$$

Conclusion and outlook

\( e^{\left( -\alpha N \right)} \)

$$\alpha=1.001$$

The influence wanishes after 6-7 layers

From 3 to 5 layers

the Fermi energy gets populated

Closest

Farthest

3 layers ABC

5 layers ABC