Search results

  1. S

    Metable states in a Laser

    A1 to B1 belongs to quantum dynamics, and A1 to A2 is due to thermal diffusion. Eletron itself doesn't know which state it should go, but the detail physical process will decide where the electron is going
  2. S

    Metable states in a Laser

    I do not get your point, either. Here's my suggestion. Metastable state is in company with a certain state. In general, there is a small gap between their energy levels (Metastable level belows certain one). Given 2 certain states, A and B, and suppose their have some metastable states...
  3. S

    Spin direction through ferromagnetic material

    You have to clarify what kind of ferromagnetic material is. there is no common answer for such a question. Give you a suggestion, please refer to the concept of spin valve.
  4. S

    Weak Anti Localisation concept

    Abstracted from Wikipedia, "In a system with spin-orbit coupling the spin of a carrier is coupled to its momentum. The spin of the carrier rotates as it goes around a self-intersecting path, and the direction of this rotation is opposite for the two directions about the loop. Because of this...
  5. S

    How does or does not BCS theory explain Meissner's Effect?

    In my knowledge, BCS did make a deep prediction in the situation of the weak electromagnetic field of type-I superconductor. Please refer to the book <theory of superconductivity> written by J. R. Schrieffer, who is the third person in BCS theory. Surely spontaneous symmetry breaking and...
  6. S

    Density-density interaction in Luttinger liquids

    Agree with OhYoungLions. Fourier transformation. The variable x in Eq. (6) strictly accords with momentum space。
  7. S

    How does or does not BCS theory explain Meissner's Effect?

    That was one of significant paper exciting everyone in the field of superconductor. In history of superconductor,"two current" model (Normal current and superconducting one) was first proposed by London brothers, explaining such zero-resistance conducting phenomenon. Company with...
  8. S

    What happens when you connect a ptype semiconductor to a metal conductor?

    The electric properties of a metal can be viewed as a highly degenerated N-type semiconductor. Therefore, P-metal can be treated as a pn diode. And it properties depends, as what yasir.ustb stated, on the work function of each materials.
  9. S

    Negative absorption peak in FTIR

    Something are exciting over the UV illumination processes.
  10. S

    What's the relationship between phonon spectrum and thermal conductivity

    Thank you! You really give me a lesson. Noted the eq. 6 in the paper you given. The thermal conductivity to be calculated requires not only the group volecity v but also the relaxation time torr. Please refer to "proposal for a single molecule field effect transistor for phonons" (Phys...
  11. S

    Impurity State Green's functions

    The intermediate term is the Self-energy term. It is calculated by infinite iteration. It also can be solved in the limit of Born approximation The detail solution you may find please refer to the "Many particle physics" authored by G. Mahan. Please take a good book to learn Green's function...
  12. S

    Cold temperature measurement

    It requires ultra high vaccum. And the cooling technology can be utilized is "Laser cooling" and "Magnetic refrigeration".
  13. S

    What's the relationship between phonon spectrum and thermal conductivity

    To comparison for the thermal conductivity of two different materials, you need to know the respective velocity of phonon. Without the velocity, it is hard to do anything. I dont know what phonon spectrum you have. Generally, the spectrum respresents the number of phonon (axis Y) at each...
  14. S

    Impedance in a superconductor

    There are one thing we need to clarify. For the second kind superconductor, as called high temperature superconductor, the magnetic flux can be enter into the superconducting bulk, and it will be pined at the center of defect. Around the flux, one can image a superconducting circuit current is...
  15. S

    Band bending

    Yes, the amount of potential change depends on the donor concentration. Or we can say, the degree of the conduction (valence) band bending will be affected due to the dopant.
  16. S

    What's the relationship between phonon spectrum and thermal conductivity

    It's hard to get the formula of thermal conductivity only by the spectrum. Because: The spectrum is analyzed when the material is under thermal equilibrium, which suggesting the temperature of the material is a fixed value, i.e. T0. During the analysis of thermal conductivity, two different...
  17. S

    High Temperature Superconductivity

    Who get the complete theory for H-Tc Supercon~, who gain the Nobel Prize.
  18. S

    I've read that ferromagnetism is a quantum mechanical phenomenon and

    In understanding the Ferromagnetism theory, you'd better look in Heisenberg theory. Heisenberg is the first man using the asymmetry exchanging of electron wavefunction to explain successfully the origination of magnetism (including Ferro- and Antiferro- magnetism).
  19. S

    I've read that ferromagnetism is a quantum mechanical phenomenon and

    What you said is called " correlation " and the system you mentioned are strong correlation system. Where tolds us the phase of spin A is correlated to spin B, which is different from the "coherence". He is asking whether or not the ferromagnetism comes from the coherence of electrons. It...
  20. S

    I've read that ferromagnetism is a quantum mechanical phenomenon and

    Ferromagnetism is caused by the wave properties of electrons. There is nothing can be related to the coherence in the origination of Ferromagnetism. But we do study the spin dynamics of a chain of magnetic lattice by the "spin wave theory". Please link to the following URL, you may get...
  21. S

    Spintronics vs GMR Effect

    GMR denotes such the special materials which behave a giant difference in resistance under the various magnetic field. One may observe GMR in a composited device and also in some Perovskite materials. Spintronics is a general concept of the device design, which includes GMR-device, such as spin...
  22. S

    I've read that ferromagnetism is a quantum mechanical phenomenon and

    Ferromagnetism is a quantum mechanical phenomenon because it is originated from the asymmetry of wave function exchanging between two fermions, i.e. electrons, which can not be understood in the classical mechanism.
  23. S

    Semiconductor Carrier Concentration Basics

    Please refer to the book "Simon M. Sze, 3rd, Physics of Semiconductor Devices"
  24. S

    I'm confused

    I am not familiar with these equations, but I try to give some opinions for discussion. The problem is that there will be an unexpected term, i.e. exp(i*q), if the B(m)B(m+1) are transformed in K-space. As I learned, B(m)B(m+1) denotes the transition process between state m and state m+1. The...
  25. S

    Ohmic junction in Cat's-whisker detector

    I suggest a method usually used in our experiment. Depositing Au film on the sample first, and then you have 2 choices: 1. sticking the detecting wire by sliver adhesive. 2. preparation with the indium electrode.
  26. S

    Question about Fields?

    The field travels by the wave-type. We do not say the B field propagate from the wire. It is said that the B field is changing from 0 to some value in intensity, which is the result of the propagation of electromagnetic wave from the wire after you switched.
  27. S

    Relation between Energy & Data

    Is this a Atomic, Solid State, or Comp. Physical problem? data transfer rate = bitwidth * frequency / 8 ; unit= bits/second
  28. S

    Maximum distance of quantum tunneling using an STM

    And the MUCH HIGHER voltage is no helpful. There's two reason: 1. Additional electrical noise will be introduced. 2. New physical phenomenon will be introduced, i.e. electron emission in a strong electric field.
  29. S

    Maximum distance of quantum tunneling using an STM

    In theoretically, there is no exact limitation for the distance. But In realitically, farther the distance, much more ambiguous the image you derived. That's because the tunneling current has an exponential relation with the distance, i.e. about exp(-d^0.5). If the distance is set to be far...
  30. S

    Magnetic property of Molecules

    It may be hard to have a discussion with the macroscopic magnetism in a molecule, but it is allowed to have a discussion with the spin alignment of each magnetic ion in a molecule. There are many possible states, such as ferro-alignment, antiferro-alignment, ferri-alignment. If the spin...
Top