Condensed Matter & Materials Physics — 60 Terms Defined

Hardness Condensed Matter & Materials Physics MPa or GPa (Mohs scale 1 to 10) A material's resistance to localized plastic surface deformation induced by mechanical scratching, abrasion, or indentation. H = Load / Indentation Surface Area (Mohs, Vickers, Rockwell)

Intrinsic Semiconductor Condensed Matter & Materials Physics cm⁻³ (Carrier Density) An ultra-pure semiconductor crystal containing no significant dopant impurity species, where carrier concentration is determined purely by thermal excitation across the band gap. n = p = n_i = √(N_c N_v) e^(-E_g / (2 k_B T))

Josephson Effect Condensed Matter & Materials Physics mA (Current), μV (Voltage) The quantum tunneling of Cooper pairs across a thin insulating barrier separating two superconductors (a Josephson junction). I = I_c sin(Δφ), V = (ℏ / 2e) (dΔφ / dt)

Liquid Crystals Condensed Matter & Materials Physics Dimensionless Orientational Order S States of matter possessing physical properties intermediate between conventional isotropic liquids and ordered crystalline solids. Nematic Order Parameter S = ½ ⟨3 cos² θ - 1⟩

Magnetic Domains Condensed Matter & Materials Physics μm to mm (Domain Size) Microscopic regions within a ferromagnetic material where atomic magnetic moments are aligned parallel in a uniform direction. Domain Wall Energy E_total = E_exchange + E_anisotropy

Majority & Minority Carriers Condensed Matter & Materials Physics cm⁻³ (Carrier Density) The classification of charge carriers in a doped semiconductor based on their relative concentrations. N-Type: n_majority = N_D, p_minority = n_i² / N_D

Malleability Condensed Matter & Materials Physics Qualitative / Quantitative Plastic Strain A material's physical ability to deform plastically under compressive stress without cracking, typically tested by hammering or rolling into thin sheets. Compressive strain tolerance without cracking

Martensitic Transformation Condensed Matter & Materials Physics Transformation Temperature M_s A rapid, diffusionless solid-state phase transformation driven by collective lattice shear displacement of atoms. Diffusionless shear transformation: Austenite (FCC) → Martensite (BCT)

Meissner Effect Condensed Matter & Materials Physics T (Magnetic Flux Density B) The active expulsion of magnetic flux from the interior of a superconductor as it cools below its critical temperature T_c. B_internal = 0, M = -H (Perfect Diamagnetism)

Metamaterials Condensed Matter & Materials Physics Dimensionless Index n < 0 Artificially engineered composite structures designed with subwavelength resonant features that display electromagnetic properties not found in natural materials. n_refractive = - √(ε_r μ_r) (Negative Refractive Index)

Miller Indices Condensed Matter & Materials Physics Dimensionless Notation System A standardized three-integer crystallographic notation system (h k l) used to specify direction vectors and orientation of planes in a crystal lattice. (h k l) = Reciprocals of lattice axis intercepts

N-type Semiconductor Condensed Matter & Materials Physics cm⁻³ (Electron Concentration) An extrinsic semiconductor in which pentavalent donor impurities create an excess concentration of free electrons as majority charge carriers. n ≈ N_D ≫ p, n p = n_i²

Non-Newtonian Fluids Condensed Matter & Materials Physics Pa·s (Apparent Viscosity η) Fluids whose shear viscosity changes depending on applied shear rate, stress magnitude, or shear history. τ = K (du / dy)^n (n ≠ 1)

P-type Semiconductor Condensed Matter & Materials Physics cm⁻³ (Hole Concentration) An extrinsic semiconductor in which trivalent acceptor impurities create an excess concentration of positive holes as majority charge carriers. p ≈ N_A ≫ n, n p = n_i²

Peltier Effect Condensed Matter & Materials Physics W (Cooling / Heating Rate) The absorption or emission of heat at the junction of two dissimilar electrical conductors when an electric current flows across it. Q_rate = Π_AB I = (S_A - S_B) T I

Phonon Condensed Matter & Materials Physics eV or J (Phonon Energy) A quantized collective vibrational wave excitation traveling through the periodic atomic or molecular lattice of a solid. E = (n + ½) ℏ ω, p_crystal = ℏ q

Piezoelectric Effect Condensed Matter & Materials Physics C/N or m/V (Piezoelectric Coefficient d) The generation of electric polarization charge in non-centrosymmetric crystals when subjected to mechanical stress (and vice versa). Direct: P_i = d_ijk σ_jk; Reverse: ε_jk = d_ijk E_i

Poisson's Ratio Condensed Matter & Materials Physics Dimensionless Ratio (-1 to 0.5) The ratio of transverse lateral strain to axial longitudinal strain in a material subjected to uniaxial stress. ν = -ε_transverse / ε_axial = -(Δd / d₀) / (ΔL / L₀)

Polaron Condensed Matter & Materials Physics Quasiparticle Mass A composite quasiparticle consisting of a conduction electron (or hole) bound together with its surrounding self-induced lattice polarization distortion cloud in an ionic crystal. m*_polaron = m* (1 + α_coupling / 6)

Quantum Confinement Effect Condensed Matter & Materials Physics eV (Confinement Energy Shift) The shift and quantization of electronic energy levels when charge carriers are confined within spatial dimensions smaller than their De Broglie wavelength. E_confinement ∝ 1 / L² (When dimension L ≤ De Broglie wavelength)

Quantum Hall Effect Condensed Matter & Materials Physics Ω (Von Klitzing Constant R_K ≈ 25812.807 Ω) A quantum mechanical version of the Hall effect observed in 2D electron gases at low temperatures and intense magnetic fields, where Hall resistance is quantized in integer multiples of h/e². R_H = h / (ν e²), ν = 1, 2, 3...

Reciprocal Lattice Condensed Matter & Materials Physics m⁻¹ (Reciprocal Distance) The Fourier transform space of a real-space crystal lattice, where every point corresponds to a set of parallel lattice planes in the real crystal. b₁ = 2π (a₂ × a₃) / (a₁ · (a₂ × a₃)), G · R = 2π n

Seebeck Effect Condensed Matter & Materials Physics μV/K (Seebeck Coefficient S) The direct conversion of a temperature gradient into an electrical voltage across a conductor or semiconductor. V = S ΔT = S (T_hot - T_cold)

Semiconductor Condensed Matter & Materials Physics S/m (Electrical Conductivity) A class of crystalline solids possessing electrical conductivity between that of conductors and insulators, controllable by temperature, light, or doping. σ = e (n μ_e + p μ_h), n_i = √(N_c N_v) e^(-E_g / (2 k_B T))