Naman Gupta, Masters student with Prof. David Hawthorn
Introduction to the physics of high-Tc superconductivity
Superconductivity
was
discovered
in
1911
in
elemental
metals
by
K.
Onnes.
Until
the
1980s,
physicists
believed
that
the
Bardeen–Cooper–Schrieffer
(BCS)
theory
—
which
describes
most
of
the
physics
of
conventional
superconductivity
—
barred
superconductivity
at
temperatures
greater
than
30
K.
In
1986,
physicists
G.
Bednorz
and
A.
Müller
at
the
IBM
Laboratory
in
Zurich
reported
that
they
have
created
a
material
(a
Lanthanum
based
cuprate)
that
became
superconducting
at
35
K.
Shortly
after,
other
research
groups
found
similar
materials
that
became
superconducting
at
around
90
K.
Currently,
the
highest
transition
temperature
known
is
around
140
K
at
ambient
pressure.
In
this
meetup,
I
will
give
a
brief
introduction
to
the
standing
problem
of
high-Tc
superconductivity
(which
is
not
described
by
the
BCS
theory)
and
briefly
talk
about
different
competing
phases
and
orders
observed
on
the
cuprate
phase
diagram.
Furthermore,
I
will
introduce
one
of
the
experimental
techniques
to
probe
such
orders,
called
Resonant
X-Ray
Scattering
(REXS),
if
time
permits.
References:
1. From quantum matter to high-temperature superconductivity in copper oxides: https://www.nature.com/articles/nature14165
Tianze Zou, Masters student with Prof. Jan Kycia
Noise sources in low-level voltage measurements
When
measuring
voltage
from
the
sample
during
an
experiment,
the
noise
is
mixed
in
the
detected
signal.
Understand
the
sources
and
magnitude
of
noise
can
help
to
explain
the
results
from
a
low-level
voltage
measurement.
The
first
part
of
the
talk
is
a
checklist
of
different
types
of
noise,
especially
in
the
Hall
voltage
measurement
of
thermoelectric
materials.
The
second
part
is
to
use
the
Agilent
34420A
nano
voltmeter
as
an
example
to
talk
about
the
specifications
section
of
a
voltmeter
and
its
input
noise.
References:
1.
Agilent
technologies.
Agilent
34420A
nano
volt/micro
Ohm
meter
user
guide.
2003
2.
Keithley
Instruments.
Low-level
measurements:
precision
DC
current,
voltage,
and
resistance
measurements.
4th
edition,
1993.
These seminars consist of two 20 minute talks, with 10 minutes for questions and discussion.
We try to keep these talks general and for a broader audience with a basic understanding of condensed matter and quantum mechanics. It’s a monthly meetup by and for graduate students and post-docs; to talk about their research, learn new topics and share interesting ideas. If you have any questions or suggestions, feel free to contact us at qmgradtalks@gmail.com.