32
3 Experiment
10 -5
10 -6
10 -7
296K
77K
4.2K
10 -8
10 -9
10 -10
100
1000
10000
f (Hz)
s
Fig. 3.11 Measured thermal noise of an electrical resistor at three different temperatures. Figure
reproduced from Ref. [4]
Naively one might anticipate magnetic monopoles to exhibit thermal noise akin
to electronic Johnson noise (Fig. 3.11)
S V (ω, T ) =
4k B T R
1 + ω 2 τ 2
(3.4)
Here S V (ω, T ) is the open-circuit voltage fluctuations in a resistor R as a function
of temperature T and frequency ω.
However our experimental observation was strikingly different from Johnson
noise. The low temperature dataset in our experiments sat at a higher plateau
height than the high temperature dataset (Fig. 3.10), whereas the opposite is true
for thermal noise from a resistor. This suggested that perhaps a different mechanism
was needed to explain the microscopic mechanism behind magnetization noise we
were observing.
Noise from generation and recombination (GR) of electrons and holes in
semiconductors exhibits unanticipated temperature dependence. The plateau height
of this electronic GR noise fell with rise in temperature [5]. The temperature
and frequency dependence of such GR noise [5] looked similar to experimentally
measured flux noise from Dy 2 Ti 2 O 7 (Fig. 3.12).
Thermal noise in a resistor is generated by random motion of electrons due
to their kinetic energy which is directly proportional to temperature. Generationrecombination noise occurs due to thermally stimulated generation of electron-hole
3 Experiment
10 -5
10 -6
10 -7
296K
77K
4.2K
10 -8
10 -9
10 -10
100
1000
10000
f (Hz)
s
Fig. 3.11 Measured thermal noise of an electrical resistor at three different temperatures. Figure
reproduced from Ref. [4]
Naively one might anticipate magnetic monopoles to exhibit thermal noise akin
to electronic Johnson noise (Fig. 3.11)
S V (ω, T ) =
4k B T R
1 + ω 2 τ 2
(3.4)
Here S V (ω, T ) is the open-circuit voltage fluctuations in a resistor R as a function
of temperature T and frequency ω.
However our experimental observation was strikingly different from Johnson
noise. The low temperature dataset in our experiments sat at a higher plateau
height than the high temperature dataset (Fig. 3.10), whereas the opposite is true
for thermal noise from a resistor. This suggested that perhaps a different mechanism
was needed to explain the microscopic mechanism behind magnetization noise we
were observing.
Noise from generation and recombination (GR) of electrons and holes in
semiconductors exhibits unanticipated temperature dependence. The plateau height
of this electronic GR noise fell with rise in temperature [5]. The temperature
and frequency dependence of such GR noise [5] looked similar to experimentally
measured flux noise from Dy 2 Ti 2 O 7 (Fig. 3.12).
Thermal noise in a resistor is generated by random motion of electrons due
to their kinetic energy which is directly proportional to temperature. Generationrecombination noise occurs due to thermally stimulated generation of electron-hole