Physics 431 - Advanced Laboratory: Condensed Matter Physics
Experiments in condensed matter physics. Examples are electron diffraction, nuclear magnetic resonance, statistics of electronic noise, superconductivity, and the Mössbauer effect
David B. Pengra
Office: Physics/Astronomy Building, Room B256A
Hours & Location
Room B248, Physics/Astronomy Building
Section A – Monday & Wednesday, 1:30–4:20
Section B – Tuesday & Thursday, 1:30–4:20
First 30-45 minutes may be used for lecture and general comments. In the event of online instruction, the sections will be subdivided into Zoom tutorials following initial lecture. See below for details.
Required Reading/Viewing Material
http://courses.washington.edu/phys431 (Standard URL links to Canvas page)
There is no required text. Material will be provided through the course website.
- Experiments in Modern Physics, Adrian C. Melissinos (Academic Press, San Diego, CA, 1966 or 2nd ed, 2003).
- The Art of Experimental Physics, Daryl W. Preston and Eric R. Dietz (John Wiley & Sons, New York, 1991).
- Introduction to Solid State Physics, Charles Kittel (John Wiley & Sons), any edition.
The 43x series of advanced laboratories are intended to provide a bridge between introductory labs, which are mostly "canned," in the sense that there is a fixed sequence of activities and a fairly rigid analysis to perform, and the kind of open-ended research found in real experiments, where you don't really know what will happen or how you should interpret the results. The physics itself is also more complicated than in the intro labs, both in terms of the underlying phenomena and the operation and interpretation of the experimental apparatus.
Measurement techniques, data analysis, and experiment interpretation form the three main emphases of the advanced labs. The first, measurement techniques, concern the things one usually associates with a lab course: experimental apparatus and its use. Measurement techniques in condensed matter span the range of nearly all experimental physics: techniques of spectroscopy (associated with atomic physics and astronomy) and particle detection (associated with nuclear physics) are used, as are measurements of light, magnetic fields, temperature, pressure, and other thermodynamic quantities. In nearly all cases, such measurements are converted to electrical signals for analysis. The phenomena of condensed matter physics are similarly diverse. This lab course has among its collection experiments in superconductivity, the thermodynamics of 2-d matter, the Hall effect, optical properties of metal films, nuclear magnetic resonance and its use in characterizing material properties, electron diffraction and crystal structure, and the amazing energy sensitivity of the Mössbauer effect to measure the magnetic field inside metallic iron.
The advanced labs focus much more on data analysis and experiment interpretation than introductory labs. Data analysis include basic tasks often called data reduction, usually done with a variety of computer programs and computer coding, and further analysis of the reduced data to look at it in different ways, i.e., with different types of graphs, with fits to complex curves, and to consider any calibration steps. Often, the goal of data analysis is to derive final results from the measurements to compare to predictions from theory or to the results of other experiments. In some cases uncertainty calculations must be carried out to complete one's interpretation of the results. This lab will introduce the use of Python coding and useful Python packages in basic data analysis, curve-fitting, and making plots.
Interpretation of experimental results is distinct from data analysis. To interpret the results means to construct a story to explain them within the framework of physical theory, and to note and describe trends, patterns and anomalies in the data. Interpretation also combines the physics of the phenomena being measured (e.g., spin echoes in NMR) with the physics of the apparatus (e.g., the magnet, pulse generator and sequence, and pickup coil). You will be asked to do more than take data and write code: ultimately your goal is to understand and be able to explain the physics of both the experiment technique and the phenomena under study with it.
Physics 431 Online?
The first experiment will be run "online." As of January 2022, the decision from UW administration is to hold the first week of classes online. To accommodate this need the first experiment will be conducted in this manner. Taking a lab course online is a very different experience than in-person.
"Online lab" - what does that even mean? When you think of a "lab," you think of an experience in which you gather with your partners around a lab bench to manipulate apparatus. It is a hands-on activity of turning knobs, connecting wires, operating oscilloscopes and the like. This kind of experience is the foundation of all "in-person" lab courses. Learning of essential skills and a direct encounter with the phenomena are to be found in such courses, and this part of a "lab" cannot be replaced by purely online tools.
You may wonder with the loss of such practical hands-on experience how any "lab" could be done online. This loss is real and should not be downplayed. However, in actual experimental research, hardware manipulation and direct data collection usually forms only a small part of an experimental project. Indeed, if one conducts experiments at certain large facilities, such as a telescope or particle accelerator, one may never set foot in the lab itself, since the apparatus may be inaccessible (orbiting around the earth or in a desert in Australia), or it may be too specialized and delicate to allow anyone other than trained technicians to operate it (such as a synchrotron beamline at Brookhaven National Laboratory). Even when you have all of the apparatus to yourself in a single room, most of your time and effort will not be on taking data. Instead, you spend your days (and sometimes nights) staring at your data, writing code, making graphs, deriving formulas, checking units, staring at other peoples' data, talking to your colleagues, reading the literature, staring at your data, and finally writing your paper.
Online labs will concentrate on these aspects. The experiment operation part will be presented in video form, and the videos will mainly deal with how the apparatus is assembled and used, and what the experiment looks like when it is running properly. Data sets will be recorded in a form that most closely matches what you would do yourself were you to be in the lab room; these may be handwritten tables and notes, digital files produced by data collection software, or photographs of oscilloscope traces. After that, you will carry out the rest of the experimental investigation in the same manner that you would in the normal in-person version of the experiment.
"Learning goals" are the most important skills and understanding you should expect to learn by taking this course. At the end of this Condensed Matter Physics Laboratory course, you should be able to
- Explain the basic concepts and operation of a variety of measurement techniques used in the experiments you perform.
- Describe how the measurements reveal the underlying phenomena being studied in terms of the physical operation and chain of cause and effect in each experiment.
- Carry out complete numerical analysis of experimental data using Python and common computer libraries (numpy, LMFit, matplotlib, etc.)
- Explain features in experimental data in terms of known physics, and point out features of data that may not be captured by the expected models.
The following are rules. The first two are safety rules and are required by University policy and Washington State law.
- No food or drink may be consumed in the lab. Washington State Law forbids the consumption of food or drink in these labs because they are officially "radiation laboratories:" there are radioactive substances in the lab.
- No students may work in the lab without the presence of lab staff.
The next two concern your participation and what is expected of you in the course. These may be subject to modification by the instructor, depending on circumstance.
- Experimental groups are limited to three persons. With four persons or more, there is not enough to do to keep everyone busy.
- Each student must carry out their own data analysis and write their own individual report. Students will work together on experiment operation, data recording, and record keeping, and they are encouraged to discuss their results with each other (and with other students) but each must independently create their own individual analysis computer coding and their own written reports.
Every person is welcome in this course. Instances of discrimination (e.g., shunning, belittling, bullying, harassment) for any reason (e.g., ethnicity, religion, sexual orientation, gender identity, different-ability, or political beliefs) will incur thorough investigation and possible sanction through University approved processes. If you believe you have been subject to such discrimination, please contact the instructor directly, or see University Policies for information on how to contact University officials.
The experiments will duplicate some foundational discoveries in condensed matter physics. All are associated with Nobel-Prize winning research, and the techniques used in them continue to be used in current research. This means that each experiment will give only a brief introduction to a deep, rich and complex sub-field in CM physics; indeed, one could easily spend 10 weeks on any one of the experiments and its related phenomena.
Each experimental cycle will include between 3 and 4 class meetings (i.e., be 2 weeks in length). All assignments associated with an experiment should be completed before starting a new experiment. The first meetings of a cycle will mostly involve learning the apparatus and making measurements; later meetings will mostly involve data analysis and interpretation.
Grades will be derived from (1) Daily Participation (Day X), (2) the Group Notebook (GN), (3) the Individual Analysis (IA), and (4) the Individual Report (IR). More details on each of these is given elsewhere, but briefly, the Group Notebook is the group's data collection and analysis record. It includes information about the apparatus, links to data sets, and copies of hand-written notes or calculations, and may pull items from members' Individual Analysis. The Group Notebook will consist of a document prepared on Google Docs, submitted for grading as a PDF. The Individual Analysis is a Jupyter Notebook written in Python, and submitted as a PDF for grading. The Individual Report may include a written summary of the experiment and/or answers to specific questions concerning the interpretation of the experiment, also submitted as a PDF to Canvas.
Daily Participation credit is awarded as you show up to class, either in person to work with your partners, or via the record kept by Zoom for attendance to online meetings.
There is no final exam (or any exam). Your grade is based on the work submitted.
Attend class every scheduled session. Lectures will be given at the beginning of most sessions, especially at the beginning of each cycle. You also need to meet with your group to carry out the measurements as well as work on data analysis and discuss your interpretations. It is expected that students will work approximately 9 hours/week on this course, 6 hours/week in the lab and 3 hours/week at home. A full experimental cycle should take about 18 hours to complete, sometimes less, other times more. Over each experimental cycle, students should plan to accomplish the following tasks during the course sessions and at home.
- Watch any videos associated with the current experiment. These give overview of the experiment and how the apparatus is to be used. If the experiment is run completely online you will need to watch these videos multiple times to learn the experiment sufficiently. Not all experiments will have videos; for these you will get more direct instruction in the lab. (0-4 hours, depending on instruction mode)
- If Online: Attend the live Zoom sessions: (1) the overview/general comments at beginning of class period and (2) the tutorial discussion as scheduled for your group. (0.5 hrs first meeting, 1 hrs second meeting)
- Do the experiment: assemble and learn to operate apparatus, take data, document the experiment in your Group Notebook. If the lab is online, attend the tutorial sessions for your group and participate in the discussions. (2-6 hours, depending on instruction mode)
- Carry out data reduction and analysis in your Jupyter notebook for the Individual Analysis. (5 hours)
- Annotate, discuss, and check each other's contributions to the Group Notebook (4-5 hours)
- Write your Individual Report, based on assigned prompt(s). (2 hours)
In-Person Lab: Class Meetings
Most class meetings will start with a lecture or whole-class discussion about what the day's tasks will be. Toward the end of the term, when every group is working on a different experiment, the whole class discussion will be brief. In these cases, you may be expected to review the theory & experiment videos, or there may be a focused meeting on the experiment between your group and a TA or instructor.
During most of the meeting time students will work with their group on the experiment and data analysis. See Working Groups below for details. You are expected to attend the full scheduled period.
Participation credit will be awarded based on an attendance record taken by the instructor or TA. Late arrival or early departure may result in a lower participation grade.
In the event that you are unable to attend in person, you may coordinate with the instructor to attend remotely and work with your group via a Zoom session. This would happen, for example, if you contracted a mild or asymptomatic case of COVID-19 or needed to quarantine but could otherwise attend to your courses.
Online Lab: Zoom Meetings
If an experiment cycle is to be run online there will be scheduled Zoom meetings. Each class period will contain two different Zoom meetings.
The Lecture Meeting will start promptly at 1:30 pm, Pacific Time, and last about 30 minutes, sometimes less. All students in the section are expected to attend because this will be the meeting where information concerning the course as a whole will be discussed, for example, class management and due dates, general questions about the week's activities, or additional lecture material not included in the videos. The Lecture Meeting will be automatically recorded and saved in the Zoom folder.
The Tutorial Meeting(s) will start at a later time (e.g., 2:30 or 3:00) and consist of approximately half the students in the section (5-9 persons), comprising 2 to 3 experiment groups. It will last 30 minutes. The second meeting will provide participation credit. The purpose of the second meeting is for you and your partners to discuss with the instructor, TAs, and other students topics related to the experiment. These topics may come from prompts provided by the instructors or from your own contributions to Slack for the experiment. The second meeting will not be recorded.
To earn participation credit, you must attend the Tutorial Meeting. Attendance will be verified from the list of attendees for the Zoom meeting.
Office hours. In addition to the scheduled meetings above, the instructor and TAs may be available on Zoom for "office hours" at other times during the week. The schedule for these office hours will be worked out as the course progresses. You may also request specific times to meet via Canvas email or Slack notification.
Course materials include two different types of videos.
Theory Lectures are about 15-40 minutes in length. These are voice-over-slide videos that discuss the important theoretical ideas behind the week's experiments. The focus of the "theory" is to help you make sense of the experiments themselves: how the apparatus works, how/where the high-energy particles come from, and how to understand the ways that the experiment illustrates the underlying physics. The longer videos are copies of Zoom sessions from a previous version of the class.
Experiment Operation and Data Collection videos show an experiment in detail: what the apparatus is, how it is assembled, how the electronics are configured and connected together, and any other important physical detail you would need to know in order to operate it. The videos will also show how data are collected, plus other measurements needed for calibration or analysis. Experiment videos will be broken up into sections of variable length, typically between 5 and 25 minutes each. For example, one video may give an overview of the apparatus, another may delve into its setup and calibration, and a third may show how data are collected.
Not all experiments have the same number and/or duration of videos. Experiments that have less video material will have more in-person instruction.
Research is a collaborative process. Most scientific work is done in teams, some quite large. Even if you are a solo theorist, you need to talk to others to refine your ideas, brainstorm and challenge assumptions. Thus, learning how to work in a group is essential. In experimental research, projects are broken down into specific tasks to be accomplished by subject experts (e.g., coding, hardware, sample preparation) and those who may be learning the field (e.g., grad students).
You will be expected to form a group of 2-3 persons in your section. Group membership will be discussed during the first class meeting. You may already know people in the class you would like to work with. We will have a class discussion on working styles and your own and others' experience: For example, are you a strong computer coder or are you just beginning to learn? Do you like to plan your tasks in detail or just start fiddling with the data? Which would you rather do: experiments or theory?
After class, you should join a group by adding your name to a Google Doc linked on the main page. Ideally, you should communicate with possible group members before you form a group. The group memberships will be posted on the main page. Any students not in a group by the time of the second class meeting will be assigned to a group by the instructor.
Group members are not bound to the same group for the duration of the course, but if possible, those groups working well together will be preserved.
What Your Group Should Do
At minimum, your group must decide which members are primarily responsible for which tasks to complete the Group Notebook. Other members will be expected to review the work entered into the Group Notebook, comment on it and correct it, if necessary.
For each experiment there will be a set of tasks assigned to the group. For example, to create a diagram of the apparatus, to record and plot a data set, to perform basic data reduction, to carry out a particular calculation, or to do outside reading on a topic and write up a few paragraphs on it. Your group should decide who is primarily responsible for a particular task.
Members should also plan to rotate tasks from experiment to experiment. In other words, do not always have the same person draw the apparatus diagram, or carry out basic data reduction coding.
The other main purpose of the group is to work together to accomplish the data analysis tasks that should be completed by every member. Such tasks are important enough that these will be assigned to all students. However, it is expected that your group may work together and help each other solve these problems.
The "group notebook" is the primary product of the working group. It should be created with a collaboration platform such as Google Docs. The group document should be made accessible to the TAs and instructor so that they can view and comment on it during the course of the experiment. The easiest way to do this is create such a document on Google Docs or Microsoft OneDrive and link it to your Slack channel.
What Goes in the Group Document?
To complete the group document, use the task list posted on the experiment page. It lists tasks to be completed and some information on how to accomplish them.
Each person should indicate their contribution by initials and date. This is standard scientific record-keeping practice. Do not "back-date" entries into the notebook, but be honest. Entries need to be made roughly equally by every member of the team.
More information on what should go into Group Notebooks, such as expectations for graphs, apparatus diagrams and annotations, discussion of data and results, inclusion of calculations and computer code, etc., are in Getting Started with Group Notebooks.
Individual Data Analysis Assignments
Some data analysis assignment will be broken out of the group document and assigned separately to all students. You may think of these like "homework" for a lecture class, but distinct from the writing focus of the Individual Reports.
There are two reasons for making such assignments not part of the group.
First, such assignments usually concern core concepts, such as creating a calibration, or finding an important quantity with a line fit. Everyone in the class should know how to do these things, not just the one person who might be assigned to that task in the group.
Second, among the learning goals of this course is building skills with computation as applied to experimental physics. Data analysis tasks will be carried out with Python on Jupyter Notebooks. This is part of an overall department effort to teach computation within the physics major. The use of Python is based upon current trends in physics research, data science generally, and the growth and maturation of collaborative tools associated with Python. See Python and Jupyter Notebooks for more information.
Each student must also write and submit their own Individual Report, as a PDF uploaded to a Canvas assignment. The structure and content of the report will be described in the assignment, and will vary as the course proceeds, but there are a few common aspects:
- It must conform to strict formatting rules and length limits. Typically, a report must be between 1 and 4 pages, be typed, single-spaced, and use 11 or 12 point font and 1 inch margins.
- It must be written well, with complete, grammatically correct sentences and structured paragraphs.
- It must address the writing prompt: typically questions about the experiment.
- It should have an opening paragraph to provide context so that the reader can understand what the report is about without having read the writing prompt (or done the experiment).
Some experiments have been adapted for online instruction. When the course is conducted online, everyone will work on the same experiment.The experiments are listed in scheduled order for a completely online course:
Johnson and Shot Noise and Fundamental Constants
Pulsed Nuclear Magnetic Resonance
As noted above, the first experiment will be online. If we are able to teach the rest of the course in person, each group will work on a different experiment, based on a sign-up sheet. The experiments that can only be done in-person are:
The Hall effect
Surface plasmon resonance
Physical adsorption of gases
Groups may sign up for any experiment they have not already done. Links to information about these experiments are posted on the main course page.
Overall grade portions are 35% Group Notebook, 25% Individual Analysis, 30% Individual Reports, 10% Participation. These are further broken down as described below.
Group document grading will reflect "real-world" assessments: the kinds of assessments that are typical in work environments and active research. Notebook assessments will be listed as letter grades A, B, C, D, F which correspond to numerical grades 4, 3, 2, 1, 0, (or 100%, 75%, 50%, 25%, 0%) and are based on the typical workplace assessments outstanding, exceeds expectations, meets expectations, does not meet expectations, nothing to assess. These may also have +/- refinements ("+" adds 0.3 to the numerical grade, "–" subtracts 0.3, i.e., +/- 7.5%).
Although the group notebook is nominally the product of the group, students will be graded according to their own contributions.
Grades will depend on
- Form and format: Entries need to be initialed and dated. Notebook should be available to all members and to the TAs and instructor.
- Timeliness: Add information to the notebook as you do the experiment. A notebook mostly created after the experiment is done will get a lower grade.
- Context: Entries should explain what is recorded and what it means. Lack of context is the main reason notebooks receive low grades.
- Completeness: Everything produced by the group that the group needs should be in the notebook: raw data, apparatus diagrams, pictures of the setup, plots, equipment settings or operations you would need to duplicate the measurements. But: you should NOT copy Python code from the Python assignment unless you specifically discuss it in the context of some point you want to make.
- Discussion and interpretation: Take some time to write down how you understand the experiment and what it means. Make your discussion quantitative and based on clear physics reasoning.
- Corrections and comments: Did you get a different result from your partner? If so, you should notice it and say so. Do you think that an entry needs more context? If so, provide that context, initial it, and get credit for it. Failure to pay attention to your partners' entries will lower your own grade.
Individual Data Analysis
Individual data analysis assignments will be done in Jupyter notebooks on the JupyterHub for the course, converted to HTML, and uploaded to canvas for grading. They will be graded according to the letter scale used for the Group document (A-F).
The Individual Report will be subject to grading as follows:
If it is turned in by the due date (or a mutually agreed upon extension of the due date) it will be graded on a 3 level scale, corresponding to typical decisions made by scientific journals: accepted (A), accepted with revisions (AwR), and rejected (R). These will correspond to letter/numeric grades of A/4.0, B/3.0, and F/0.0. Reports that earn AwR or R may be resubmitted once. Exceptions to the submission process may occur if there is not enough time to grade, return, and resubmit, such as at the end of the term. A report that falls below a grade of AwR on its final submission will be graded B-, ..., R. Reports that are originally graded R (0) but not resubmitted will retain the grade of 0.
Resubmissions are due within 1 week of the initial grade decision. The last report of the term will only be graded once, unless you have arranged with the TA or instructor on acceptable due dates.
If it is turned in past the due date, even if submitted within the grace period (see below), it will be graded once on an A, AwR, B-, ..., R scale. (Note there will be no A-, B+ grades, to make the scale consistent with the preferred submission-cycle scale)
|Contribution||Scale||Percent of total|
|Participation||A - F||10%|
|Group notebook||A - F||35%|
|Individual Data Analysis||A - F||25%|
|Individual Report||A, AwR, R or A, AwR - F||30%|
Due dates & Extensions
- There is one due date for the final version of the Group Notebook and Individual Analysis: midnight (i.e., 11:59 pm) on the last class day of the experiment cycle (typically Thursday or Friday night, depending of section).
- The due date for the Individual Report is at midnight (11:59 pm) on the first class day of the following experiment cycle, e.g., Tuesday or Wednesday night, depending on section.
- There is an automatic grace period of 48 hours following the due dates. Think of this as an automatic extension, should you need to talk to the TA or instructor. You do not need to ask for this extension.
- Extensions beyond the grace period will be granted, but they must be requested before the end of the grace period. A new date will be assigned to work granted an extension. New dates will be decided by the TA or instructor. These will typically be set to 2-3 days following the request. There is no grace period attached to an extension; the only thing that will change is the availability date.
- Each student must individually request an extension.
- Without an extension granted and set in Canvas, the assignment will become unavailable following the grace period.
If you need an extension on the Individual Report and you want to have it subject to revise/resubmit grading, you must ask for the extension before the due date. Extensions requested after the due date will make the paper be graded once.
The final grade will be calculated according to the formula
Thus, to earn a 4.0, you need about 95%.
Writing ("W") Option
A writing "W" credit will be awarded to any student who earns at least 4 "Accept" grades on their Individual Reports.
A number of University of Washington policies pertain to this course. See University Policies.