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Abbreviations and Symbols
VIS
Visible (spectral range)
vdW
van der Waals
WS 2
Tungsten disulfide
WSe 2
Tungsten diselenide
WTe 2
Tungsten ditelluride
X
Exciton, neutral exciton
X*
Charged exciton, also referred to as trion
XP
Exciton–polariton
X d
Dark exciton
XX
Biexciton, neutral biexciton
ZJU
Zhejiang University (Hangzhou)
Symbols
h
Planck’s quantum of action
=
h
2π
≈ 1.054572 · 10
−34 J s
k B
≈ 8.617333 · 10
−5 eV/K, Boltzmann constant
c
= 2.99792458 · 10
8 m
s
, speed of light
π
≈ 3.141593
k
Wave-vector
k ||
Transversal component of the wave-vector, corresponding to an in-plane
momentum, for instance, in the plane of a quantum well; [k ] = μm
−1
k ⊥
Longitudinal component of the wave-vector, corresponding to an out-ofplane momentum, for instance, vertical to the plane of a quantum well
e
≈ 1.602177 · 10
−19 C, elementary charge
m e
≈ 9.109384 · 10
−31 kg, free electron mass
ε 0
≈ 8.854188 · 10
−12 As
Vm
, dielectric constant, vacuum permittivity
ε r
Relative dielectric constant (vacuum: 1 per definition); high frequency
constant: ε r (∞) , background constant ε b ; in general, frequency-dependent
complex dielectric function ε r (ω)
ε
= ε 0 · ε r , permittivity of a medium
˜
n(ω)
Frequency-dependent complex refractive index
n
Refractive index; due to its relationship to ˜
n, in general frequency
dependent
(also used as symbol representing the particle density n = N /V, number
N divided by volume V )
κ
Extinction coefficient; due to its relationship to ˜
n, in general frequency
dependent
α
Absorption coefficient; due to its relationship to the extinction coefficient
and thereby ˜
n, in general frequency dependent
(also used as symbol representing the linearity factor in input–output
measurements)
Abbreviations and Symbols
VIS
Visible (spectral range)
vdW
van der Waals
WS 2
Tungsten disulfide
WSe 2
Tungsten diselenide
WTe 2
Tungsten ditelluride
X
Exciton, neutral exciton
X*
Charged exciton, also referred to as trion
XP
Exciton–polariton
X d
Dark exciton
XX
Biexciton, neutral biexciton
ZJU
Zhejiang University (Hangzhou)
Symbols
h
Planck’s quantum of action
=
h
2π
≈ 1.054572 · 10
−34 J s
k B
≈ 8.617333 · 10
−5 eV/K, Boltzmann constant
c
= 2.99792458 · 10
8 m
s
, speed of light
π
≈ 3.141593
k
Wave-vector
k ||
Transversal component of the wave-vector, corresponding to an in-plane
momentum, for instance, in the plane of a quantum well; [k ] = μm
−1
k ⊥
Longitudinal component of the wave-vector, corresponding to an out-ofplane momentum, for instance, vertical to the plane of a quantum well
e
≈ 1.602177 · 10
−19 C, elementary charge
m e
≈ 9.109384 · 10
−31 kg, free electron mass
ε 0
≈ 8.854188 · 10
−12 As
Vm
, dielectric constant, vacuum permittivity
ε r
Relative dielectric constant (vacuum: 1 per definition); high frequency
constant: ε r (∞) , background constant ε b ; in general, frequency-dependent
complex dielectric function ε r (ω)
ε
= ε 0 · ε r , permittivity of a medium
˜
n(ω)
Frequency-dependent complex refractive index
n
Refractive index; due to its relationship to ˜
n, in general frequency
dependent
(also used as symbol representing the particle density n = N /V, number
N divided by volume V )
κ
Extinction coefficient; due to its relationship to ˜
n, in general frequency
dependent
α
Absorption coefficient; due to its relationship to the extinction coefficient
and thereby ˜
n, in general frequency dependent
(also used as symbol representing the linearity factor in input–output
measurements)