lecture 1
Condensed Matter Physics:
Ebinazar Namdas and Peter Jacobson
The University of Queensland
Brisbane, Australia
- Quick overview of admin details
- Why condensed matter?
Today
Teaching staff
Dr. Carla Verdi
Dr. Peter Jacobson
A/ Prof.EbinazarNamdas
- Lecturers (All lectures and tutorials will be delivered in class).
- Lecture # 1-12; 20-22 : A/Prof. Ebinazar Namdas
- Lecture # 13-19; 23-26 : Dr. Carla Verdi
- Lecture # 27-33: Dr. Peter Jacobson
- Tutorials:
|
Assessment Task |
Weighting |
||
|
|
6 Assignments |
30% |
|
|
Presentation |
Topic related to Condensed Matter Physics |
10% |
|
|
|
Examination Period |
60 % |
Assignments
LearningResources
Teaching Timetable
Up on Blackboard
Policies and procedures
University policies and procedures apply to all aspects of student life. As a UQ student, you must comply with University-wide and program-specific requirements, including the:
Policies and procedures
Why condensed matter?
Typical quantum problems
In quantum you’ve dealt with ‘particle in a box’ type problems
Wavefunction of a singleparticle
Or simple atomic systems like hydrogen
But we want to explain
Not particles in a box
Not simple atomic systems
The collectivebehaviour of electrons in materials
Roadmap
Lattice & symmetry: what the material is (structure, reciprocal space)
Electrons & excitations: what the material does (bands, quasiparticles, phonons)
Phases & phenomena: what the material becomes (order, superconductivity, topology/correlation)
What are we doing when we do science?
What are we doing when we do science?
Practically, we:
- Build models
- Test them by measuring
- And improve measurements/bounds
- Keep what is useful within a regime
- Energy or time scales
What are we doing when we do science?
Practically, we:
- Build models
- Simplifications that make quantitative predictions
- Test them by measuring
- And improve measurements/bounds
- Keep what is useful within a regime
- Energy or time scales
Route to scientific progress:New phenomenon (exp/theory) → New model → New tools → New questions
Popper and Kuhn
Two big ideas (yes, others, but this is an intro!)
Not mutually exclusive
- Karl Popper –falsification/falsifiability
- Good theories make risky predictions that could be wrong
- Experiments can rule out models
1962
1934/1959
Popper and Kuhn
Two big ideas (yes, others, but this is an intro!)
Not mutually exclusive
- Karl Popper –falsification/falsifiability
- Good theories make risky predictions that could be wrong
- Experiments can rule out models
- Thomas Kuhn –paradigms
- Most of the time we do normal science following the known and accepted rules
- Anomalies occur, require changes in how we think (paradigm shift)
1962
1934/1959
Popper and Kuhn
Two big ideas (yes, others, but this is an intro!)
Not mutually exclusive
- Karl Popper –falsification/falsifiability
- Good theories make risky predictions that could be wrong
- Experiments can rule out models/parameter ranges
- Thomas Kuhn –paradigms
- Most of the time we do normal science following the known and accepted rules
- Anomalies occur, require changes in how we think (paradigm shift)
- Fits the standard Quantum Mechanics and Relativity narrative (but other ways to think)
1962
1934/1959
Or TL;DR
Karl Popper –how we test our models/assumptions
Thomas Kuhn –how we decide we need something radically new
1962
1934/1959
How does this fit to condensed matter?
How does this fit to condensed matter?
Condensed matter incorporates aspects of many areas:
quantum, E&M, field theory, statistical mechanics
How does this fit to condensed matter?
Condensed matter incorporates aspects of many areas:
quantum, E&M, field theory, statistical mechanics
What counts as an explanation?
How does this fit to condensed matter?
Condensed matter incorporates aspects of many areas:
quantum, E&M, field theory, statistical mechanics
What counts as an explanation?
We want to consider:
- Scale (energy, time, spatial dimension)
- Effective picture at that scale
- Degrees of freedom (quasiparticles)
- Constraints or approximations (and what we can ignore)
How does this fit to condensed matter?
Condensed matter incorporates aspects of many areas:
quantum, E&M, field theory, statistical mechanics
What counts as an explanation?
We want to consider:
- Scale (energy, time, spatial dimension)
- Effective picture at that scale
- Degrees of freedom (quasiparticles)
- Constraints or approximations (and what we can ignore)
Wedon’toftensolvethefullmicroscopicproblem,wechoosetherightpartstoaddresstheproblem.
How should we think about condensed matter?
Phil Anderson –formulated the major question in condensed matter physics
How should we think about condensed matter?
- Many interacting particles means new effective laws
- New entities appear (quasiparticles, order parameters)
- Need to go beyond the few-particle problem
- Emergence
Same atom, different outcomes
Diamond and Graphite
- Both only contain carbon
Different symmetry of C atoms
D –insulator, G –conductor
D –transparent, G –opaque
Structure –electronic bands –properties
How should we think about condensed matter?
What changes in many body systems?
- Degrees of freedom (quasiparticles)
- Organize by symmetry (or more recently, topology)
- predict collective behavior and measure
Condensed Matter Physics
Condensed matter physics is about how unexpectedproperties arise from interactions in materials
Nature Reviews Physics4,508 (2022)
Condensed Matter Physics
Anderson emphasised“broken symmetry” as the central organisingprinciple of condensed matter
- Different phases means different symmetry of the ground state
- crystals (broken translation symmetry)
- magnets (broken spin-rotation symmetry)
- superconductors (broken gauge symmetry)
- But also, connections to quantum field theory!
Motion around the trough is associated with the Goldstone mode. Motion perpendicular to the trough is associated with the "Higgs boson".
Some light reading
“As a theoretical physicist, one of Anderson's greatest strengths was his uncanny ability to strip away the details from a complicated problem and identify its key elements. He would then construct a mathematical model (description) which retained only those elements. Invariably, the models he developed were simple enough to analyzein detail, yet complex enough to exhibit the physical behaviorhe hoped to understand.”
Prologue and Introduction posted on Blackboard
Tools we need to understand emergence
- What are crystals, how are atoms ordered?
- Arrangement of atoms affects wavefunctions overlap
- How do electrons move through materials?
- What is the balance of KE and PE for electrons in solids
- How do crystals move?
- What are quasiparticles?
Where we are now in condensed matter
Topology: protection of wavefunctions from perturbations
Correlations: electrons act collectively
Moiré materials/flat bands: tune interaction with geometry
Some rough numbers
- 130k articles (letters) published in PRL since founded in 1958
- PRL is often considered the top physicsjournal
- 50k articles in the Condensed Matter section
- Caveat, 40k articles not categorized
- ~ 38% of articles in PRL are on Condensed Matter as a lower bound
Physical Review Letters
Listen to this page as a podcast (about 1 hour, generated with AI).
Generate & play 1-hour podcast