Condensed matter: from a material to its evidence

An electrical current can reveal an energy gap, a magnetic arrangement or a charge packet moving through a sensor. Start with the effect you want to understand, then follow the apparatus to what was measured and what it supports.

Try a controlled experiment

Eight instruments, eight different questions

Each instrument uses a defined teaching model and synthetic data. Follow its visible process to the resulting curve or readout, and open the model notes for its assumptions.

Control a transistor
Carrier injection and output curves
Cross a material interface
Band offsets and carrier injection
Make blue light
Recombination and efficiency
Move an image as charge
Clocked transfer and readout noise
Rotate a spin valve
Relative magnetization and resistance
Thread a superconducting loop
Flux and two-junction interference
Compare repeated switching
Thermal and tunneling escape limits
Watch flux enter a superconductor
Critical fields near the transition

Reading path · C-R1

Materials that control current and light

Follow the device from carrier supply to a measured electrical or optical signal.

Thermionic emission: a hot surface sets a current limit
How did Richardson separate electrons leaving a hot metal from currents caused by gas?
The first transistor: a small input controlled a larger current
What did the point-contact experiment demonstrate that an ordinary resistor could not?
Esaki’s tunnel diode: more voltage could give less current
Why did a heavily doped junction develop a falling section in its current curve?
Heterostructures: an interface became a device control
What changes when a junction joins two different semiconductor materials?
Integrated circuits: putting a circuit into one piece of material
Why was integrating components a different achievement from inventing the transistor?
Giant magnetoresistance: relative magnetization changed the resistance
Why did alternating magnetic layers carry current differently when their magnetizations aligned?
CCD imaging: move the charge before measuring it
How did a clocked chain of charge wells turn an optical exposure into an electrical image?
Graphene: a thin flake became an electrical experiment
What made the 2004 thin-carbon experiment more than a successful exfoliation?
Blue LEDs: a wide band gap was only the beginning
Why did efficient blue light require advances in crystal growth and hole injection?

Reading path · C-R2

Cold liquids and superconducting order

Read what cooling revealed, which theories followed and how independent measurements tested them.

Liquid helium: building access to a new temperature range
Why was liquefying helium a scientific instrument as well as a technical feat?
Landau’s helium: describe the liquid’s excitations
How did collective excitations connect heat, sound and superfluid motion?
Kapitsa’s helium flow: viscosity depended on how it was tested
Why did helium below the lambda transition defeat a single ordinary-viscosity picture?
BCS theory: one paired state had to explain several experiments
Why did an excitation gap matter more than another explanation of zero resistance?
Giaever’s junction: current revealed the superconducting gap
How could a thin insulating layer turn electrical current into spectroscopy?
Josephson’s prediction: phase could drive a zero-voltage current
What was new about a supercurrent through an insulating barrier?
Cuprate superconductivity: a ceramic changed the temperature scale
What evidence turned an unusual resistance drop into a new superconducting material family?
Helium-three: a pressure anomaly changed its interpretation
How did pressure and nuclear resonance reveal a transition in liquid helium-three?
Ginzburg–Landau theory: describe how superconducting order varies
How could a phenomenological field predict interfaces and magnetic response before microscopic pairing was known?
Abrikosov vortices: magnetic flux entered without ending superconductivity
How can a superconductor contain magnetic flux and remain superconducting between the flux cores?
Leggett’s helium-three: resonance identified the pairing order
Why could a tiny spin-dependent interaction reveal the structure of a strongly paired liquid?

Reading path · C-R3

The evidence for dilute-gas condensation

Start with preparation and release images, then distinguish occupation, coherence and superfluid response.

BEC in a dilute gas: the expanding cloud carried the evidence
How did preparation and time-of-flight images establish a Bose–Einstein condensate?

Reading path · C-R4

A collective circuit variable became quantum

Compare switching statistics with microwave evidence for discrete levels.

Macroscopic quantum circuits: escape and resonances told different parts
How did a biased Josephson circuit reveal tunneling and discrete energy levels?

Reading path · C-R5

Magnetism, disorder and topological response

Separate the roles of magnetic order, coherent disorder and many-electron correlations.

Néel’s magnetic order: zero net moment need not mean disorder
How can a material have ordered atomic moments without behaving like a simple ferromagnet?
Anderson localization: disorder could stop diffusion
Why can a quantum wave remain localized even when the lattice still has connected paths?
Mott’s insulating states: counting bands was not enough
Why can electrons fail to conduct when a simple independent-electron picture suggests a metal?
Van Vleck’s susceptibility: excited states influence a quiet magnet
How can virtual changes of quantum state contribute to magnetization?
Integer quantum Hall effect: a plateau became a resistance reference
Why was a flat Hall-resistance interval more informative than a single crossing of a predicted value?
Fractional quantum Hall effect: the plateau required a correlated liquid
What went beyond the integer Hall picture when the lowest Landau level was only partly filled?
Vortex unbinding: a two-dimensional fluid could change without ordinary order
How can vortex pairs drive a transition in two dimensions?
Haldane’s spin chains: integer and half-integer spins parted ways
Why did changing the spin quantum number alter the low-energy behavior of an antiferromagnetic chain?
Thouless and Hall topology: an integer organized the response
How did the geometry of occupied quantum states explain robust integer Hall conductance?

Reading path · C-R6

A material choice improved measurement

Follow thermal expansion from a measured alloy property to precision instruments.

Invar: a length standard that changed less with temperature
How did an unusual nickel–steel alloy improve precision measurement?

Follow the connections through time

Experiments, theories and the later prizes

The first date marks a milestone discussed in the article; the second marks its Nobel contribution. Some advances are experiments, others are theories. Open a reading for the sequence and its sources.

Open the 32-stop evidence timeline